1 Introduction to splanchnology.
2 Digestive system.
3 Anatomy of the respiratory system.
Lesson # 2
Theme 1. Introduction to splanchnology.
SPLANCHNOLOGY is doctrine about viscera, which disposed in thoracic, abdominal and pelvic cavities, also in head and neck. Internal organs may be divided into digestive, respiratory, urinary and genital systems and endocrine glands.
The digestive system is a group of organs that work like wrecking equipment to break down the chemical components of food, through the use of digestive juices, into tiny nutrients which can be absorbed to generate energy for the body. Digestion begins in the mouth with the teeth, which grind the food into small particles; the tongue, a powerful muscle which detects "good" and "bad" flavours in food and manipulates the food between the teeth for chewing, and saliva, a watery fluid which lubricates chewing and swallowing and begins the process of digestion. The digestive system begins in the mouth, continues in the pharynx (throat) and oesophagus and into the "gut" region: the stomach, small and large intestines, the rectum and the anus. Food is chewed, pulped and mixed with saliva to become a soft mass which will easily travel down the oesophagus. The tongue traps the food and forces it into the throat, which is a mass of muscles and tissues which transports food into the gut system for final processing and distribution. The liver and the pancreas also secrete digestive juices that break down food as it passes through the digestive ducts. Not all that we eat can be digested, so the waste must be disposed of in an efficient way. It may not be a savoury ending for the food or drink we thought was so delicious in the mouth, but it is just as important for our health.
Theme 2. Digestive system.
The apparatus for the digestion (Apparatus Digestorius; Organs Of Digestion) of the food consists of the digestive tube and of certain accessory organs.
The Digestive Tube (alimentary canal) is a musculomembranous
The accessory organs are the teeth, for purposes of mastication; the three pairs of salivary glands—the parotid, submandibular, and sublingual—the secretion from which mixes with the food in the mouth and converts it into a bolus and acts chemically on one of its constituents; the liver and pancreas, two large glands in the abdomen, the secretions of which, in addition to that of numerous minute glands in the walls of the alimentary canal, assist in the process of digestion.
The Development of the Digestive Tube.—The primitive digestive tube consists of two parts, viz.: (1) the fore-gut, within the cephalic flexure, and dorsal to the heart; and (2) the hind-gut, within the caudal flexure. Between these is the wide opening of the yolk-sac, which is gradually narrowed and reduced to a small foramen leading into the vitelline duct. At first the fore-gut and hind-gut end blindly. The anterior end of the fore-gut is separated from the stomodeum by the buccopharyngeal membrane. the hind-gut ends in the cloaca, which is closed by the cloacal membrane.
Human embryo about fifteen days old. Brain and heart represented from right side. Digestive tube and yolk sac in median section.
The Mouth.—The mouth is developed partly from the stomodeum, and partly from the floor of the anterior portion of the fore-gut. By the growth of the head end of the embryo, and the formation of the cephalic flexure, the pericardial area and the buccopharyngeal membrane come to lie on the ventral surface of the embryo. With the further expansion of the brain, and the forward bulging of the pericardium, the buccopharyngeal membrane is depressed between these two prominences. This depression constitutes the stomodeum. It is lined by ectoderm, and is separated from the anterior end of the fore-gut by the buccopharyngeal membrane. This membrane is devoid of mesoderm, being formed by the apposition of the stomodeal ectoderm with the fore-gut entoderm; at the end of the third week it disappears, and thus a communication is established between the mouth and the future pharynx. No trace of the membrane is found in the adult; and the communication just mentioned must not be confused with the permanent isthmus faucium. The lips, teeth, and gums are formed from the walls of the stomodeum, but the tongue is developed in the floor of the pharynx.
The visceral arches extend in a ventral direction between the stomodeum and the pericardium; and with the completion of the mandibular arch and the formation of the maxillary processes, the mouth assumes the appearance of a pentagonal orifice. The orifice is bounded in front by the fronto-nasal process, behind by the mandibular arch, and laterally by the maxillary processes. With the inward growth and fusion of the palatine processes, the stomodeum is divided into an upper nasal, and a lower buccal part. Along the free margins of the processes bounding the mouth cavity a shallow groove appears; this is termed the primary labial groove, and from the bottom of it a downgrowth of ectoderm takes place into the underlying mesoderm. The central cells of the ectodermal downgrowth degenerate and a secondary labial groove is formed; by the deepening of this, the lips and cheeks are separated from the alveolar processes of the maxillæ and mandible.
The Salivary Glands.—The salivary glands arise as buds from the epithelial lining of the mouth; the parotid appears during the fourth week in the angle between the maxillary process and the mandibular arch; the submandibular appears in the sixth week, and the sublingual during the ninth week in the hollow between the tongue and the mandibular arch.
Head end of human embryo of about thirty to thirty-one days.
The Tongue is developed in the floor of the pharynx, and consists of an anterior or buccal and a posterior or pharyngeal part which are separated in the adult by the V-shaped sulcus terminalis. During the third week there appears, immediately behind the ventral ends of the two halves of the mandibular arch, a rounded swelling named the tuberculum impar, which was described by His as undergoing enlargement to form the buccal part of the tongue. More recent researches, however, show that this part of the tongue is mainly, if not entirely, developed from a pair of lateral swellings which rise from the inner surface of the mandibular arch and meet in the middle line. The tuberculum impar is said to form the central part of the tongue immediately in front of the foramen cecum, but Hammar insists that it is purely a transitory structure and forms no part of the adult tongue. From the ventral ends of the fourth arch there arises a second and larger elevation, in the center of which is a median groove or furrow. This elevation was named by His the furcula, and is at first separated from the tuberculum impar by a depression, but later by a ridge, the copula, formed by the forward growth and fusion of the ventral ends of the second and third arches. The posterior or pharyngeal part of the tongue is developed from the copula, which extends forward in the form of a V, so as to embrace between its two limbs the buccal part of the tongue. At the apex of the V a pit-like invagination occurs, to form the thyroid gland, and this depression is represented in the adult by the foramen cecum of the tongue. In the adult the union of the anterior and posterior parts of the tongue is marked by the V-shaped sulcus terminalis, the apex of which is at the foramen cecum, while the two limbs run lateralward and forward, parallel to, but a little behind, the vallate papillæ.
The Palatine Tonsils.—The palatine tonsils are developed from the dorsal angles of the second branchial pouches. The entoderm which lines these pouches grows in the form of a number of solid buds into the surrounding mesoderm. These buds become hollowed out by the degeneration and casting off of their central cells, and by this means the tonsillar crypts are formed. Lymphoid cells accumulate around the crypts, and become grouped to form the lymphoid follicles; the latter, however, are not well-defined until after birth.
The Further Development of the Digestive Tube.—The upper part of the fore-gut becomes dilated to form the pharynx in relation to which the branchial arches are developed (see page 65); the succeeding part remains tubular, and with the descent of the stomach is elongated to form the esophagus. About the fourth week a fusiform dilatation, the future stomach, makes its appearance, and beyond this the gut opens freely into the yolk-sac. The opening is at first wide, but is gradually narrowed into a tubular stalk, the yolk-stalk or vitelline duct. Between the stomach and the mouth of the yolk-sac the liver diverticulum appears. From the stomach to the rectum the alimentary canal is attached to the notochord by a band of mesoderm, from which the common mesentery of the gut is subsequently developed. The stomach has an additional attachment, viz., to the ventral abdominal wall as far as the umbilicus by the septum transversum. The cephalic portion of the septum takes part in the formation of the diaphragm, while the caudal portion into which the liver grows forms the ventral mesogastrium. The stomach undergoes a further dilatation, and its two curvatures can be recognized, the greater directed toward the vertebral column and the lesser toward the anterior wall of the abdomen, while its two surfaces look to the right and left respectively. Behind the stomach the gut undergoes great elongation, and forms a V-shaped loop which projects downward and forward; from the bend or angle of the loop the vitelline duct passes to the umbilicus. For a time a considerable part of the loop extends beyond the abdominal cavity into the umbilical cord, but by the end of the third month it is withdrawn within the cavity. With the lengthening of the tube, the mesoderm, which attaches it to the future vertebral column and carries the bloodvessels for the supply of the gut, is thinned and drawn out to form the posterior common mesentery. The portion of this mesentery attached to the greater curvature of the stomach is named the dorsal mesogastrium, and the part which suspends the colon is termed the mesocolon. About the sixth week a diverticulum of the gut appears just behind the opening of the vitelline duct, and indicates the future cecum and vermiform process. The part of the loop on the distal side of the cecal diverticulum increases in diameter and forms the future ascending and transverse portions of the large intestine. Until the fifth month the cecal diverticulum has a uniform caliber, but from this time onward its distal part remains rudimentary and forms the vermiform process, while its proximal part expands to form the cecum. Changes also take place in the shape and position of the stomach. Its dorsal part or greater curvature, to which the dorsal mesogastrium is attached, grows much more rapidly than its ventral part or lesser curvature to which the ventral mesogastrium is fixed. Further, the greater curvature is carried downward and to the left, so that the right surface of the stomach is now directed backward and the left surface forward, a change in position which explains why the left vagus nerve is found on the front, and the right vagus on the back of the stomach. The dorsal mesogastrium being attached to the greater curvature must necessarily follow its movements, and hence it becomes greatly elongated and drawn lateralward and ventralward from the vertebral column, and, as in the case of the stomach, the right surfaces of both the dorsal and ventral mesogastria are now directed backward, and the left forward. In this way a pouch, the bursa omentalis, is formed behind the stomach, and this increases in size as the digestive tube undergoes further development; the entrance to the pouch constitutes the future foramen epiploicum or foramen of Winslow. The duodenum is developed from that part of the tube which immediately succeeds the stomach; it undergoes little elongation, being more or less fixed in position by the liver and pancreas, which arise as diverticula from it. The duodenum is at first suspended by a mesentery, and projects forward in the form of a loop. The loop and its mesentery are subsequently displaced by the transverse colon, so that the right surface of the duodenal mesentery is directed backward, and, adhering to the parietal peritoneum, is lost. The remainder of the digestive tube becomes greatly elongated, and as a consequence the tube is coiled on itself, and this elongation demands a corresponding increase in the width of the intestinal attachment of the mesentery, which becomes folded.
At this stage the small and large intestines are attached to the vertebral column by a common mesentery, the coils of the small intestine falling to the right of the middle line, while the large intestine lies on the left side.
The gut is now rotated upon itself, so that the large intestine is carried over in front of the small intestine, and the cecum is placed immediately below the liver; about the sixth month the cecum descends into the right iliac fossa, and the large intestine forms an arch consisting of the ascending, transverse, and descending portions of the colon—the transverse portion crossing in front of the duodenum and lying just below the greater curvature of the stomach; within this arch the coils of the small intestine are disposed . Sometimes the downward progress of the cecum is arrested, so that in the adult it may be found lying immediately below the liver instead of in the right iliac region.
Further changes take place in the bursa omentalis and in the common mesentery, and give rise to the peritoneal relations seen in the adult. The bursa omentalis, which at first reaches only as far as the greater curvature of the stomach, grows downward to form the greater omentum, and this downward extension lies in front of the transverse colon and the coils of the small intestine Above, before the pleuro-peritoneal opening is closed, the bursa omentalis sends up a diverticulum on either side of the esophagus; the left diverticulum soon disappears, but the right is constricted off and persists in most adults as a small sac lying within the thorax on the right side of the lower end of the esophagus. The anterior layer of the transverse mesocolon is at first distinct from the posterior layer of the greater omentum, but ultimately the two blend, and hence the greater omentum appears as if attached to the transverse colon . The mesenteries of the ascending and descending parts of the colon disappear in the majority of cases, while that of the small intestine assumes the oblique attachment characteristic of its adult condition.
The lesser omentum is formed, as indicated above, by a thinning of the mesoderm or ventral mesogastrium, which attaches the stomach and duodenum to the anterior abdominal wall. By the subsequent growth of the liver this leaf of mesoderm is divided into two parts, viz., the lesser omentum between the stomach and liver, and the falciform and coronary ligaments between the liver and the abdominal wall and diaphragm .
The Rectum and Anal Canal.—The hind-gut is at first prolonged backward into the body-stalk as the tube of the allantois; but, with the growth and flexure of the tail-end of the embryo, the body-stalk, with its contained allantoic tube, is carried forward to the ventral aspect of the body, and consequently a bend is formed at the junction of the hind-gut and allantois. This bend becomes dilated into a pouch, which constitutes the entodermal cloaca; into its dorsal part the hind-gut opens, and from its ventral part the allantois passes forward. At a later stage the Wolffian and Müllerian ducts open into its ventral portion. The cloaca is, for a time, shut off from the anterior by a membrane, the cloacal membrane, formed by the apposition of the ectoderm and entoderm, and reaching, at first, as far forward as the future umbilicus. Behind the umbilicus, however, the mesoderm subsequently extends to form the lower part of the abdominal wall and symphysis pubis. By the growth of the surrounding tissues the cloacal membrane comes to lie at the bottom of a depression, which is lined by ectoderm and named the ectodermal cloaca
The entodermal cloaca is divided into a dorsal and a ventral part by means of a partition, the urorectal septum which grows downward from the ridge separating the allantoic from the cloacal opening of the intestine and ultimately fuses with the cloacal membrane and divides it into an anal and a urogenital part. The dorsal part of the cloaca forms the rectum, and the anterior part of the urogenital sinus and bladder. For a time a communication named the cloacal duct exists between the two parts of the cloaca below the urorectal septum; this duct occasionally persists as a passage between the rectum and urethra. The anal canal is formed by an invagination of the ectoderm behind the urorectal septum. This invagination is termed the proctodeum, and it meets with the entoderm of the hind-gut and forms with it the anal membrane. By the absorption of this membrane the anal canal becomes continuous with the rectum. A small part of the hind-gut projects backward beyond the anal membrane; it is named the post-anal gut and usually becomes obliterated and disappears.
Oral cavity is bordered up by palate, which separates the oral cavity from the nasal cavities and the nasal part of the pharynx or nasopharynx; in front and laterally – by cheeks, from below – by oral diaphragm (formed by mylohyoid muscle). The cavity of the mouth is placed at the commencement of the digestive tube it is a nearly oval-shaped cavity, which consists of two parts: an outer, smaller portion, the vestibule, and an inner, larger part, the proper mouth cavity. Both portions communicate each other through the space behind last molars and through the fissure between upper and lower teeth. The vestibule is the slit like space between the lips, cheeks, the teeth and the gingivae. The vestibule communicates with the exterior through the orifice of the mouth - the opening, through which food and other substances pass into the oral cavity. Duct of parotid salivary gland opens into vestibule.
Upper and lower lips (labia) formed by orbicularis oris muscle covered externally by skin and internally by mucous membrane and surround the mouth are the entrance to the oral cavity. Both lips unite laterally by labial commissure. Around the oral vestibule and between the mucous membrane and the orbicularis oris muscle are located labial salivary glands. The ducts of these small glands open into the vestibule. The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the superior and inferior labial frenula. The upper lip has a median vertical groove called the philtrum. Intermediate portion red area located between the skin and the mucous membrane.
Cheeks have a muscular component - buccinator muscle. Superficial to the fascia covering this muscle is the buccal fat pad - Bisha body. It gives the cheeks their rounded contour, particularly in infants for sucking the milk. The lips and cheeks function as a unit (for example - during blowing, eating, sucking, and kissing). They act as an oral sphincter in pushing food from the vestibule to the oral cavity proper. Mucous membrane of the cheeks contains small buccal salivary glands.
Palate consists of two regions: 1. the anterior two-thirds or bony part - the hard palate. 2. the mobile posterior one-third or fibromuscular part – the soft palate. The hard palate formed by palatine processes of the maxillae and the horizontal plates of the palatine bones covered by mucous membrane, which contains small salivary glands. Posteriorly the hard palate is continuous with the soft palate. The soft palate contains a membranous aponeurosis and is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate. The soft palate or velum palatinum extends posterior inferiorly to a curved free margin from which hangs a conical process - the uvula. It separates the nasopharynx superiorly from the oropharynx inferiorly. Laterally the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal arches, between which locate the palatine tonsil. Deep to the palatal mucosa are mucous glands. The soft palate is formad by 5 muscles:
Tensor veli palatini muscle – stretches velum palatine and widens aperture of uditory tube;
Levator veli palatini muscle – lifts soft palatine;
Uvulae muscle – lifts and shortens the uvula;
Palatoglossus muscle – lowers the velum palatinum, narrows the fauceus and lifts the lingual root;
Palatopharyngeus muscle –narrows the fauceus and lifts the pharynx.
The teeth may be divided into deciduous (primary) teeth in chilhood age and permanent teeth in adult. Each tooth consists of three parts: crown, neck and root. The crown has 5 surfaces: lingual, vestibular (labial or buccal), contact (proximal and distal), occlusal. The neck is the part of the tooth between the crown and the root. The root is fixed in the alveolar socket by a fibrous periodontal ligament (gomphosis).
Tooth is composed of dentin that is covered by enamel over the crown - and cementum over the root. The pulp cavity contains connective tissue, blood vessels, and nerves. The last pass through the root canal and the apical foramen. The roots of the teeth fit into sockets called dental alveoli in the alveolar process of the mandible and maxillae. Each socket is lined with periodontal membrane.
Types of Teeth
Medial and lateral incisors - have a single root and chisel-shaped crown. Action: they cut off portions of food.
Canine - has a single root, conical crown. Action: holding and bite the food.
Premolar - has a single root, sometimes upper tooth has bifurcated root. Crown carries two tubercles. Action: crushing the food.
Molar – upper teeth have three roots, lower teeth have two roots. Crown carries 3-5 tubercles on occlusal surface. Action: grinding the food.
Formula of the deciduous (milk) teeth is 2102. Formula of the permanent teeth is 2123. It means that child before 6 years of age in each side of upper and lower jaw own 2 incisors, 1canine, no premolar and 2 molars. Permanent teeth include 2 incisors, 1canine, 2 premolars and 3 molars.
Permanent teeth of upper dental arch, seen from below.
Permanent teeth of right half of lower dental arch, seen from above
Age terms of eruption of deciduous teeth and permanent teeth:
Type of tooth
6 – 9 months
7 – 9 years
16 - 20 months
10 – 13 years
10 – 12 years
11 –15 years
12 - 15 months
6 –7 years
20 – 24 months
13 – 16 years
Third Molar ("wisdom tooth")
18 – 30 years
Order of cutting of milk teeth:
• First molars;
• Second molars.
Maxillæ at about one year.
Child should have 20 teeth till end of second year of age.
Order of eruption of permanent teeth:
• first inferior molars;
• Medial incisors and first superior molars;
• Lateral incisors;
• First premolars;
• Second premolars;
• Second molars;
• Third molars (called "wisdom tooth", present not in all person).
The complete temporary dentition (about three years), showing the relation of the developing permanent teeth.
There are 32 permanent teeth. Mutual arrangement of superior and inferior dental arches during closing the mouth called bite. There are the physiological and pathologic bites.
The gingivae are composed of fibrous tissue that is covered with mucous membrane. They are firmly attached to the margins of the alveolar processes (tooth sockets) of the jaws and to the necks of the teeth.
The tongue is situated partly in the mouth and partly in the oropharynx. It consists of three parts: apex, body and root. Also tongue has dorsum (upper surface), inferior surface, margin and median sulcus. The dorsum of the tongue carries V-shaped sulcus terminalis with foramen cecum at the apex of this sulcus. Sulcus terminalis divide dorsum linguae into anterior presulcal and posterior postsulcal parts. There is lingual tonsil on the mucous membrane of root.
Lingual frenulum attaches anterior presulcal portion to the floor of the mouth. Fimbriate plicae pass laterally from frenulum. Sublingual plica runs laterally and backward from frenulum base, also it carries sublingual caruncle. Ducts of submandibular and sublingual glands open there. The mucous membrane on the oral part of the tongue carries numerous of the papillae:
· The filiform papillae and conic papillae - contain afferent nerve endings that are sensitive to touch.
· The fungiform papillae - small and mushroom-shaped. They usually appear as pink or red spots. Contain taste receptors located in the taste buds.
The vallate papillae - are the
largest papillae (1 to
· The foliate papillae - are small lateral folds of the lingual margins. They contain taste receptors.
There are four extrinsic and four intrinsic muscles of tongue.
Extrinsic group contains four muscles:
1. THE GENIOGLOSSUS MUSCLE arises by a short tendon from the mental spine of the mandible. Insertion: enters the tongue inferiorly and its fibres attach to the entire dorsum of the tongue. Actions: depresses the tongue and its posterior part protrudes it.
2. THE HYOGLOSSUS MUSCLE arises from the body and greater horn of the hyoid bone. Insertion: the side and inferior aspect of the tongue. Actions: depresses the tongue, pulling its sides inferiorly.
3. THE STYLOGLOSSUS MUSCLE originates from the anterior border of the styloid process near its tip and from the stylohyoid ligament. Insertion: the side and inferior aspect of the tongue. Actions: lifting the tongue and curls its sides to create a trough during swallowing.
4. THE PALATOGLOSSUS MUSCLE starts from the palatine aponeurosis of the soft palate. Insertion: the side and the lateral part of the tongue. Actions: elevates the posterior part of the tongue.
The intrinsic muscles are mainly concerned with altering the shape of the tongue, making it broad or narrow. Their fibbers run in three directions.
2. THE INFERIOR LONGITUDINAL Muscle consists of a narrow band close to the interior surface of the tongue. Actions: curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.
3.THE TRANSVERSE Muscle lies deep to the superior longitudinal muscle. Origin: the fibrous lingual septum. Insertion: submucous fibrous tissue. Actions: narrows and increases the height of the tongue.
4. Vertical Muscle originates in dorsum of the tongue. Insertion: site of the tongue. Actions: flattens and broadens the tongue; acting with the transverse muscle, it increases the length of the tongue.
The Tongue (lingua) is the principal organ of the sense of taste, and an important organ of speech; it also assists in the mastication and deglutition of the food. It is situated in the floor of the mouth, within the curve of the body of the mandible.
Its Root (radix linguæ base) is directed backward, and connected with the hyoid bone by the Hyoglossi and Genioglossi muscles and the hyoglossal membrane; with the epiglottis by three folds (glossoepiglottic) of mucous membrane; with the soft palate by the glossopalatine arches; and with the pharynx by the Constrictores pharyngis superiores and the mucous membrane.
Its Apex (apex linguæ tip), thin and narrow, is directed forward against the lingual surfaces of the lower incisor teeth.
Its Inferior Surface (facies inferior linguæ under surface) is connected with the mandible by the Genioglossi; the mucous membrane is reflected from it to the lingual surface of the gum and on to the floor of the mouth, where, in the middle line, it is elevated into a distinct vertical fold, the frenulum linguæ. On either side lateral to the frenulum is a slight fold of the mucous membrane, the plica fimbriata, the free edge of which occasionally exhibits a series of fringe-like processes.
The apex of the tongue, part of the inferior surface, the sides, and dorsum are free.
The Dorsum of the Tongue (dorsum linguæ)
(Fig. 1014) is convex and marked by a median sulcus, which divides it into
symmetrical halves; this sulcus ends behind, about
The Papillæ of the Tongue are projections of the corium. They are thickly distributed over the anterior two-thirds of its dorsum, giving to this surface its characteristic roughness. The varieties of papillæ met with are the papillæ vallatæ, papillæ fungiformes, papillæ filiformes, and papillæ simplices.
The mouth cavity. The apex of the tongue is turned upward,
and on the right side a superficial dissection of its under surface has been made
The papillæ vallatæ (circumvallate
papillæ) are of large size, and vary from eight to twelve in number.
They are situated on the dorsum of the tongue immediately in front of the
foramen cecum and sulcus terminalis, forming a row on either side; the two rows
run backward and medialward, and meet in the middle line, like the limbs of the
letter V inverted. Each papilla consists of a projection of mucous membrane
from 1 to
The papillæ fungiformes (fungiform papillæ), more numerous than the preceding, are found chiefly at the sides and apex, but are scattered irregularly and sparingly over the dorsum. They are easily recognized, among the other papillæ, by their large size, rounded eminences, and deep red color. They are narrow at their attachment to the tongue, but broad and rounded at their free extremities, and covered with secondary papillæ.
The papillæ simplices are similar to those of the skin, and cover the whole of the mucous membrane of the tongue, as well as the larger papillæ. They consist of closely set microscopic elevations of the corium, each containing a capillary loop, covered by a layer of epithelium.
Muscles of the Tongue.—The tongue is divided into lateral halves by a median fibrous septum which extends throughout its entire length and is fixed below to the hyoid bone. In either half there are two sets of muscles, extrinsic and intrinsic; the former have their origins outside the tongue, the latter are contained entirely within it.
The extrinsic muscles are:
Extrinsic muscles of the tongue. Left side.
The Genioglossus (Geniohyoglossus) is a flat triangular muscle close to and parallel with the median plane, its apex corresponding with its point of origin from the mandible, its base with its insertion into the tongue and hyoid bone. It arises by a short tendon from the superior mental spine on the inner surface of the symphysis menti, immediately above the Geniohyoideus, and from this point spreads out in a fan-like form. The inferior fibers extend downward, to be attached by a thin aponeurosis to the upper part of the body of the hyoid bone, a few passing between the Hyoglossus and Chondroglossus to blend with the Constrictores pharyngis; the middle fibers pass backward, and the superior ones upward and forward, to enter the whole length of the under surface of the tongue, from the root to the apex. The muscles of opposite sides are separated at their insertions by the median fibrous septum of the tongue; in front, they are more or less blended owing to the decussation of fasciculi in the median plane.
The Hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the Styloglossus and Longitudinalis inferior. The fibers arising from the body of the hyoid bone overlap those from the greater cornu.
The Chondroglossus is sometimes described as a part
of the Hyoglossus, but is separated from it by fibers of the Genioglossus,
which pass to the side of the pharynx. It is about
A small slip of muscular fibers is occasionally found, arising from the cartilago triticea in the lateral hyothyroid ligament and entering the tongue with the hindermost fibers of the Hyoglossus.
The Styloglossus, the shortest and smallest of the three styloid muscles, arises from the anterior and lateral surfaces of the styloid process, near its apex, and from the stylomandibular ligament. Passing downward and forward between the internal and external carotid arteries, it divides upon the side of the tongue near its dorsal surface, blending with the fibers of the Longitudinalis inferior in front of the Hyoglossus; the other, oblique, overlaps the Hyoglossus and decussates with its fibers.
The intrinsic muscles are:
linguæ superior (
The Longitudinalis linguæ inferior (Inferior lingualis) is a narrow band situated on the under surface of the tongue between the Genioglossus and Hyoglossus. It extends from the root to the apex of the tongue: behind, some of its fibers are connected with the body of the hyoid bone; in front it blends with the fibers of the Styloglossus.
The Transversus linguæ (Transverse lingualis) consists of fibers which arise from the median fibrous septum and pass lateralward to be inserted into the submucous fibrous tissue at the sides of the tongue.
The Verticalis linguæ (Vertical lingualis) is found only at the borders of the forepart of the tongue. Its fibers extend from the upper to the under surface of the organ.
The median fibrous septum of the tongue is very complete, so that the anastomosis between the two lingual arteries is not very free.
Nerves.—The muscles of the tongue described above are supplied by the hypoglossal nerve.
Actions.—The movements of the tongue, although numerous and complicated, may be understood by carefully considering the direction of the fibers of its muscles. The Genioglossi, by means of their posterior fibers, draw the root of the tongue forward, and protrude the apex from the mouth. The anterior fibers draw the tongue back into the mouth. The two muscles acting in their entirety draw the tongue downward, so as to make its superior surface concave from side to side, forming a channel along which fluids may pass toward the pharynx, as in sucking. The Hyoglossi depress the tongue, and draw down its sides. The Styloglossi draw the tongue upward and backward. The Glossopalatini draw the root of the tongue upward. The intrinsic muscles are mainly concerned in altering the shape of the tongue, whereby it becomes shortened, narrowed, or curved in different directions; thus, the Longitudinalis superior and inferior tend to shorten the tongue, but the former, in addition, turn the tip and sides upward so as to render the dorsum concave, while the latter pull the tip downward and render the dorsum convex. The Transversus narrows and elongates the tongue, and the Verticalis flattens and broadens it. The complex arrangement of the muscular fibers of the tongue, and the various directions in which they run, give to this organ the power of assuming the forms necessary for the enunciation of the different consonantal sounds; and Macalister states “there is reason to believe that the musculature of the tongue varies in different races owing to the hereditary practice and habitual use of certain motions required for enunciating the several vernacular languages.”
Structure of the Tongue.—The tongue is partly invested by mucous membrane and a submucous fibrous layer.
The mucous membrane (tunica mucosa linguæ) differs in different parts. That covering the under surface of the organ is thin, smooth, and identical in structure with that lining the rest of the oral cavity. The mucous membrane of the dorsum of the tongue behind the foramen cecum and sulcus terminalis is thick and freely movable over the subjacent parts. It contains a large number of lymphoid follicles, which together constitute what is sometimes termed the lingual tonsil. Each follicle forms a rounded eminence, the center of which is perforated by a minute orifice leading into a funnel-shaped cavity or recess; around this recess are grouped numerous oval or rounded nodules of lymphoid tissue, each enveloped by a capsule derived from the submucosa, while opening into the bottom of the recesses are also seen the ducts of mucous glands. The mucous membrne on the anterior part of the dorsum of the tongue is thin, intimately adherent to the muscular tissue, and presents numerous minute surface eminences, the papillæ of the tongue. It consists of a layer of connective tissue, the corium or mucosa, covered with epithelium.
The epithelium is of the stratified squamous variety, similar to but much thinner than that of the skin: and each papilla has a separate investment from root to summit. The deepest cells may sometimes be detached as a separate layer, corresponding to the rete mucosum, but they never contain coloring matter.
The corium consists of a dense felt-work of fibrous connective tissue, with numerous elastic fibers, firmly connected with the fibrous tissue forming the septa between the muscular bundles of the tongue. It contains the ramifications of the numerous vessels and nerves from which the papillæ are supplied, large plexuses of lymphatic vessels, and the glands of the tongue.
Structure of the Papillæ.—The papillæ apparently resemble in structure those of the cutis, consisting of cone-shaped projections of connective tissue, covered with a thick layer of stratified squamous epithelium, and containing one or more capillary loops among which nerves are distributed in great abundance. If the epithelium be removed, it will be found that they are not simple elevations like the papillæ of the skin, for the surface of each is studded with minute conical processes which form secondary papillæ. In the papillæ vallatæ, the nerves are numerous and of large size; in the papillæ fungiformes they are also numerous, and end in a plexiform net-work, from which brush-like branches proceed; in the papillæ filiformes, their mode of termination is uncertain.
Glands of the Tongue.—The tongue is provided with mucous and serous glands.
The mucous glands are similar in structure to the
labial and buccal glands. They are found especially at the back part behind the
vallate papillæ, but are also present at the apex and marginal parts. In
this connection the anterior lingual glands (Blandin or Nuhn) require special
notice. They are situated on the under surface of the apex of the tongue,
one on either side of the frenulum, where they are covered by a fasciculus of
muscular fibers derived from the Styloglossus and Longitudinalis inferior. They
are from 12 to
The serous glands occur only at the back of the tongue in the neighborhood of the taste-buds, their ducts opening for the most part into the fossæ of the vallate papillæ. These glands are racemose, the duct of each branching into several minute ducts, which end in alveoli, lined by a single layer of more or less columnar epithelium. Their secretion is of a watery nature, and probably assists in the distribution of the substance to be tasted over the taste area. (Ebner.)
The septum consists of a vertical layer of fibrous
tissue, extending throughout the entire length of the median plane of the
tongue, though not quite reaching the dorsum. It is thicker behind than in front,
and occasionally contains a small fibrocartilage, about
The hyoglossal membrane is a strong fibrous lamina, which connects the under surface of the root of the tongue to the body of the hyoid bone. This membrane receives, in front, some of the fibers of the Genioglossi.
Taste-buds, the end-organs of the gustatory sense, are scattered over the mucous membrane of the mouth and tongue at irregular intervals. They occur especially in the sides of the vallate papillæ. In the rabbit there is a localized area at the side of the base of the tongue, the papilla foliata, in which they are especially abundant. They are described under the organs of the senses (page 991).
Vessels and Nerves.—The main artery of the tongue is the lingual branch of the external carotid, but the external maxillary and ascending pharyngeal also give branches to it. The veins open into the internal jugular.
The lymphatics of the tongue have been described on page 696.
The sensory nerves of the tongue are: (1) the lingual branch of the mandibular, which is distributed to the papillæ at the forepart and sides of the tongue, and forms the nerve of ordinary sensibility for its anterior two-thirds; (2) the chorda tympani branch of the facial, which runs in the sheath of the lingual, and is generally regarded as the nerve of taste for the anterior two-thirds; this nerve is a continuation of the sensory root of the facial (nervus intermedius); (3) the lingual branch of the glossopharyngeal, which is distributed to the mucous membrane at the base and sides of the tongue, and to the papillæ vallatæ, and which supplies both gustatory filaments and fibers of general sensation to this region; (4) the superior laryngeal, which sends some fine branches to the root near the epiglottis.
The Salivary Glands
—Three large pairs of salivary glands communicate with the mouth, and pour their secretion into its cavity; they are the parotid, submandibular, and sublingual.
Parotid Gland (glandula parotis).—The parotid gland, the largest of the three, varies in weight from 14 to 28 gm. It lies upon the side of the face, immediately below and in front of the external ear. The main portion of the gland is superficial, somewhat flattened and quadrilateral in form, and is placed between the ramus of the mandible in front and the mastoid process and Sternocleidomastoideus behind, overlapping, however, both boundaries. Above, it is broad and reaches nearly to the zygomatic arch; below, it tapers somewhat to about the level of a line joining the tip of the mastoid process to the angle of the mandible. The remainder of the gland is irregularly wedge-shaped, and extends deeply inward toward the pharyngeal wall.
Structures within the Gland.—The external carotid artery lies at first on the deep surface, and then in the substance of the gland. The artery gives off its posterior auricular branch which emerges from the gland behind; it then divides into its terminal branches, the internal maxillary and superficial temporal; the former runs forward deep to the neck of the mandible; the latter runs upward across the zygomatic arch and gives off its transverse facial branch which emerges from the front of the gland. Superficial to the arteries are the superficial temporal and internal maxillary veins, uniting to form the posterior facial vein; in the lower part of the gland this vein splits into anterior and posterior divisions. The anterior division emerges from the gland and unites with the anterior facial to form the common facial vein; the posterior unites in the gland with the posterior auricular to form the external jugular vein. On a still more superficial plane is the facial nerve, the branches of which emerge from the borders of the gland. Branches of the great auricular nerve pierce the gland to join the facial, while the auriculotemporal nerve issues from the upper part of the gland.
The parotid duct (ductus parotideus; Stensen’s duct) is about 7 cm. long. It begins by numerous branches from the anterior part of the gland, crosses the Masseter, and at the anterior border of this muscle turns inward nearly at a right angle, passes through the corpus adiposum of the cheek and pierces the Buccinator; it then runs for a short distance obliquely forward between the Buccinator and mucous membrane of the mouth, and opens upon the oral surface of the cheek by a small orifice, opposite the second upper molar tooth. While crossing the Masseter, it receives the duct of the accessory portion; in this position it lies between the branches of the facial nerve; the accessory part of the gland and the transverse facial artery are above it.
Structure.—The parotid duct is dense, its wall being of considerable thickness; its canal is about the size of a crow-quill, but at its orifice on the oral surface of the cheek its lumen is greatly reduced in size. It consists of a thick external fibrous coat which contains contractile fibers, and of an internal or mucous coat lined with short columnar epithelium.
Vessels and Nerves.—The arteries supplying the parotid gland are derived from the external carotid, and from the branches given off by that vessel in or near its substance. The veins empty themselves into the external jugular, through some of its tributaries. The lymphatics end in the superficial and deep cervical lymph glands, passing in their course through two or three glands, placed on the surface and in the substance of the parotid. The nerves are derived from the plexus of the sympathetic on the external carotid artery, the facial, the auriculotemporal, and the great auricular nerves. It is probable that the branch from the auriculotemporal nerve is derived from the glossopharyngeal through the otic ganglion. At all events, in some of the lower animals this has been proved experimentally to be the case.
Submandibular Gland (glandula submandibularis).—The submandibular gland is irregular in form and about the size of a walnut. A considerable part of it is situated in the submandibular triangle, reaching forward to the anterior belly of the Digastricus and backward to the stylomandibular ligament, which intervenes between it and the parotid gland. Above, it extends under cover of the body of the mandible; below, it usually overlaps the intermediate tendon of the Digastricus and the insertion of the Stylohyoideus, while from its deep surface a tongue-like deep process extends forward above the Mylohyoideus muscle.
Its superficial surface consists of an upper and a lower part. The upper part is directed outward, and lies partly against the submandibular depression on the inner surface of the body of the mandible, and partly on the Pterygoideus internus. The lower part is directed downward and outward, and is covered by the skin, superficial fascia, Platysma, and deep cervical fascia; it is crossed by the anterior facial vein and by filaments of the facial nerve; in contact with it, near the mandible, are the submandibular lymph glands.
The deep surface is in relation with the Mylohyoideus, Hyoglossus, Styloglossus, Stylohyoideus, and posterior belly of the Digastricus; in contact with it are the mylohyoid nerve and the mylohyoid and submental vessels.
The deep process of the gland extends forward between the Mylohyoideus below and externally, and the Hyoglossus and Styloglossus internally; above it is the lingual nerve and submandibular ganglion; below it the hypoglossal nerve and its accompanying vein.
The submandibular duct (ductus submandibularis; Wharton’s duct) is about 5 cm. long, and its wall is much thinner than that of the parotid duct. It begins by numerous branches from the deep surface of the gland, and runs forward between the Mylohyoideus and the Hyoglossus and Genioglossus, then between the sublingual gland and the Genioglossus, and opens by a narrow orifice on the summit of a small papilla, at the side of the frenulum linguæ. On the Hyoglossus it lies between the lingual and hypoglossal nerves, but at the anterior border of the muscle it is crossed laterally by the lingual nerve; the terminal branches of the lingual nerve ascend on its medial side.
Sublingual Gland (glandula sublingualis).—The sublingual gland is the smallest of the three glands. It is situated beneath the mucous membrane of the floor of the mouth, at the side of the frenulum linguæ, in contact with the sublingual depression on the inner surface of the mandible, close to the symphysis. It is narrow, flattened, shaped somewhat like an almond, and weighs nearly 2 gm. It is in relation, above, with the mucous membrane; below, with the Mylohyoideus; behind, with the deep part of the submandibular gland; laterally, with the mandible; and medially, with the Genioglossus, from which it is separated by the lingual nerve and the submandibular duct. Its excretory ducts are from eight to twenty in number. Of the smaller sublingual ducts (ducts of Rivinus), some join the submandibular duct; others open separately into the mouth, on the elevated crest of mucous membrane (plica sublingualis), caused by the projection of the gland, on either side of the frenulum linguæ. One or more join to form the larger sublingual duct (duct of Bartholin), which opens into the submandibular duct.
Structure of the Salivary Glands.—The salivary glands are compound racemose glands, consisting of numerous lobes, which are made up of smaller lobules, connected together by dense areolar tissue, vessels, and ducts. Each lobule consists of the ramifications of a single duct, the branches ending in dilated ends or alveoli on which the capillaries are distributed. The alveoli are enclosed by a basement membrane, which is continuous with the membrana propria of the duct and consists of a net-work of branched and flattened nucleated cells.
The alveoli of the salivary glands are of two kinds, which differ in the appearance of their secreting cells, in their size, and in the nature of their secretion. (1) The mucous variety secretes a viscid fluid, which contains mucin; (2) the serous variety secretes a thinner and more watery fluid. The sublingual gland consists of mucous, the parotid of serous alveoli. The submandibular contains both mucous and serous alveoli, the latter, however, preponderating.
The cells in the mucous alveoli are columnar in shape. In the fresh condition they contain large granules of mucinogen. In hardened preparations a delicate protoplasmic net-work is seen, and the cells are clear and transparent. The nucleus is usually situated near the basement membrane, and is flattened.
In some alveoli are seen peculiar crescentic bodies, lying between the cells and the membrana propria. They are termed the crescents of Gianuzzi, or the demilunes of Heidenhainm and are composed of polyhedral granular cells, which Heidenhain regards as young epithelial cells destined to supply the place of those salivary cells which have undergone disintegration. This view, however, is not accepted by Klein. Fine canaliculi pass between the mucus-secreting cells to reach the demilunes and even penetrate the cells forming these structures.
In the serous alveoli the cells almost completely fill the cavity, so that there is hardly any lumen perceptible; they contain secretory granules imbedded in a closely reticulated protoplasm. The cells are more cubical than those of the mucous type; the nucleus of each is spherical and placed near the center of the cell, and the granules are smaller.
Both mucous and serous cells vary in appearance according to whether the gland is in a resting condition or has been recently active. In the former case the cells are large and contain many secretory granules; in the latter case they are shrunken and contain few granules, chiefly collected at the inner ends of the cells. The granules are best seen in fresh preparations.
The ducts are lined at their origins by epithelium which differs little from the pavement form. As the ducts enlarge, the epithelial cells change to the columnar type, and the part of the cell next the basement membrane is finely striated.
The lobules of the salivary glands are richly supplied with bloodvessels which form a dense net-work in the interalveolar spaces. Fine plexuses of nerves are also found in the interlobular tissue. The nerve fibrils pierce the basement membrane of the alveoli, and end in branched varicose filaments between the secreting cells. In the hilus of the submandibular gland there is a collection of nerve cells termed Langley’s ganglion.
Accessory Glands.—Besides the salivary glands proper, numerous other glands are found in the mouth. Many of these glands are found at the posterior part of the dorsum of the tongue behind the vallate papillæ, and also along its margins as far forward as the apex. Others lie around and in the palatine tonsil between its crypts, and large numbers are present in the soft palate, the lips, and cheeks. These glands are of the same structure as the larger salivary glands, and are of the mucous or mixed type.
Parotid gland is situated in retromandibular fossa: front and lower from auricle, laterally from ramus mandibulae and posterior margin of masseter muscle. This is – compound alveolar gland, which produces serous secret. Parotid duct opens on the cheeks into vestibule of mouth cavity opposite the second superior molar. Parotid gland has superficial part and deep part also can be additional parotid gland, which disposes on surface of masticator muscle closely to parotid duct.
Sublingual gland lies in the floor of the mouth between the mandible and the genioglossus muscle. This is compound alveolar-tubular gland, it produces mucous secret. Greater sublingual duct opens on sublingual papilla near submandibular duct (sometimes the ducts open together as one). Lesser sublingual ducts open along sublingual fold.
Transition of parietal peritoneum into visceral peritoneum realizes by derivatives: ligament, mesentery and omentum. If organ covered by peritoneum from all sides, such position is called intraperitoneal; if from three sides - mesoperitoneal position; if only one side - extraperitoneal or retroperitoneal.
Abdominal cavity is limited:
· above - by diaphragm
· anteriorly and laterally - by muscles, fasciae, skin
· behind - by lumbar and sacral portions of backbone and lumbar muscles
· from below – by bones, ligaments and muscles of pelvis.
Abdominal cavity contains the organs of digestive and urogenital systems and spleen.
Front view of the thoracic and abdominal viscera. a. Median plane. b b. Lateral planes. c c. Trans tubercular plane.
d d. Subcostal plane. e e. Transpyloric plane
Regions.—For convenience of description of
the viscera, as well as of reference to the morbid conditions of the contained
parts, the abdomen is artificially divided into nine regions by imaginary
planes, two horizontal and two sagittal, passing through the cavity, the edges
of the planes being indicated by lines drawn on the surface of the body. Of the
horizontal planes the upper or transpyloric is indicated by a line
encircling the body at the level of a point midway between the jugular notch
and the symphysis pubis, the lower by a line carried around the trunk at the
level of a point midway between the transpyloric and the symphysis pubis. The
latter is practically the intertubercular plane of Cunningham, who
pointed out 163 that its level corresponds with the prominent and easily defined
tubercle on the iliac crest about
The middle region of the upper zone is called the epigastric; and the two lateral regions, the right and left hypochondriac. The central region of the middle zone is the umbilical; and the two lateral regions, the right and left lumbar. The middle region of the lower zone is the hypogastric or pubic region; and the lateral regions are the right and left iliac or inguinal.
The pelvis is that portion of the abdominal cavity which lies below and behind a plane passing through the promontory of the sacrum, lineæ terminales of the hip bones, and the pubic crests. It is bounded behind by the sacrum, coccyx, Piriformes, and the sacrospinous and sacrotuberous ligaments; in front and laterally by the pubes and ischia and Obturatores interni; above it communicates with the abdomen proper; below it is closed by the Levatores ani and Coccygei and the urogenital diaphragm. The pelvis contains the urinary bladder, the sigmoid colon and rectum, a few coils of the small intestine, and some of the generative organs.
When the anterior abdominal wall is removed, the viscera are partly exposed as follows: above and to the right side is the liver, situated chiefly under the shelter of the right ribs and their cartilages, but extending across the middle line and reaching for some distance below the level of the xiphoid process. To the left of the liver is the stomach, from the lower border of which an apron-like fold of peritoneum, the greater omentum, descends for a varying distance, and obscures, to a greater or lesser extent, the other viscera. Below it, however, some of the coils of the small intestine can generally be seen, while in the right and left iliac regions respectively the cecum and the iliac colon are partly exposed. The bladder occupies the anterior part of the pelvis, and, if distended, will project above the symphysis pubis; the rectum lies in the concavity of the sacrum, but is usually obscured by the coils of the small intestine. The sigmoid colon lies between the rectum and the bladder.
When the stomach is followed from left to right it is seen
to be continuous with the first part of the small intestine, or duodenum, the
point of continuity being marked by a thickened ring which indicates the
position of the pyloric valve. The duodenum passes toward the under surface of
the liver, and then, curving downward, is lost to sight. If, however, the
greater omentum be thrown upward over the chest, the inferior part of the
duodenum will be observed passing across the vertebral column toward the left
side, where it becomes continuous with the coils of the jejunum and ileum.
These measure some
The spleen lies behind the stomach in the left hypochondriac region, and may be in part exposed by pulling the stomach over toward the right side.
The glistening appearance of the deep surface of the abdominal wall and of the surfaces of the exposed viscera is due to the fact that the former is lined, and the latter are more or less completely covered, by a serous membrane, the peritoneum.
the Peritoneum (Tunica Serosa)—The peritoneum is the largest serous membrane in the body, and consists, in the male, of a closed sac, a part of which is applied against the abdominal parietes, while the remainder is reflected over the contained viscera. In the female the peritoneum is not a closed sac, since the free ends of the uterine tubes open directly into the peritoneal cavity. The part which lines the parietes is named the parietal portion of the peritoneum; that which is reflected over the contained viscera constitutes the visceral portion of the peritoneum. The free surface of the membrane is smooth, covered by a layer of flattened mesothelium, and lubricated by a small quantity of serous fluid. Hence the viscera can glide freely against the wall of the cavity or upon one another with the least possible amount of friction. The attached surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue, termed the subserous areolar tissue. The parietal portion is loosely connected with the fascial lining of the abdomen and pelvis, but is more closely adherent to the under surface of the diaphragm, and also in the middle line of the abdomen.
The space between the parietal and visceral layers of the peritoneum is named the peritoneal cavity; but under normal conditions this cavity is merely a potential one, since the parietal and visceral layers are in contact. The peritoneal cavity gives off a large diverticulum, the omental bursa, which is situated behind the stomach and adjoining structures; the neck of communication between the cavity and the bursa is termed the epiploic foramen (foramen of Winslow). Formerly the main portion of the cavity was described as the greater, and the omental bursa as the lesser sac.
The peritoneum differs from the other serous membranes of the body in presenting a much more complex arrangement, and one that can be clearly understood only by following the changes which take place in the digestive tube during its development.
To trace the membrane from one viscus to another, and from the viscera to the parietes, it is necessary to follow its continuity in the vertical and horizontal directions, and it will be found simpler to describe the main portion of the cavity and the omental bursa separately.
Vertical Disposition of the Main Peritoneal Cavity (greater sac)—It is convenient to trace this from the back of the abdominal wall at
the level of the umbilicus. On following the peritoneum upward from this level
it is seen to be reflected around a fibrous cord, the ligamentum teres (obliterated
umbilical vein), which reaches from the umbilicus to the under surface of
the liver. This reflection forms a somewhat triangular fold, the falciform
ligament of the liver, attaching the upper and anterior surfaces of the
liver to the diaphragm and abdominal wall. With the exception of the line of
attachment of this ligament the peritoneum covers the whole of the under
surface of the anterior part of the diaphragm, and is continued from it on to
the upper surface of the right lobe of the liver as the superior layer of
the coronary ligament, and on to the upper surface of the left lobe as the superior
layer of the left triangular ligament of the liver. Covering the upper and
anterior surfaces of the liver, it is continued around its sharp margin on to
the under surface, where it presents the following relations: (a) It
covers the under surface of the right lobe and is reflected from the back part
of this on to the right suprarenal gland and upper extremity of the right
kidney, forming in this situation the inferior layer of the coronary
ligament; a special fold, the hepatorenal ligament, is frequently
present between the inferior surface of the liver and the front of the kidney.
From the kidney it is carried downward to the duodenum and right colic flexure
and medialward in front of the inferior vena cava, where it is continuous with
the posterior wall of the omental bursa. Between the two layers of the coronary
ligament there is a large triangular surface of the liver devoid of peritoneal
covering; this is named the bare area of the liver, and is attached to
the diaphragm by areolar tissue. Toward the right margin of the liver the two
layers of the coronary ligament gradually approach each other, and ultimately
fuse to form a small triangular fold connecting the right lobe of the liver to
the diaphragm, and named the right triangular ligament of the liver. The
apex of the triangular bare area corresponds with the point of meeting of the
two layers of the coronary ligament, its base with the fossa for the inferior
vena cava. (b) It covers the lower surface of the quadrate lobe, the
under and lateral surfaces of the gall-bladder, and the under surface and
posterior border of the left lobe; it is then reflected from the upper surface
of the left lobe to the diaphragm as the inferior layer of the left
triangular ligament, and from the porta of the liver and the fossa for the
ductus venosus to the lesser curvature of the stomach and the first
Peritoneal cavity is complex of fissure between abdominal organs and walls lined by parietal and visceral sheets that contain serous liquid. It can be subdivided into superior storey and inferior storey, also cavity of lesser pelvis.
Superior storey of peritoneal cavity positioned between diaphragm and level of mesocolon of transverse colon. It contains:
• hepatic bursa surrounds right hepatic lobe and gallbladder;
• pregastric bursa accommodates left hepatic lobe and anterior wall of stomach;
• omental bursa is situated behind lesser omentum and it is in touch with posterior stomach surface.
Lesser omentum is formed by double peritoneal sheet that forms of hepatogastric ligament and hepatoduodenal ligament. Lesser omentum carries common bile duct, portal vein and proper hepatic artery (DVA).
Hepatic bursa communicates with omental bursa by the medium of epiploic foramen (of Winslow). Last limited from above by caudate lobe of the liver, from below - by superior part of duodenum, anteriorly - hepatoduodenal ligament, behind - by parietal sheet of peritoneum.
Greater omentum develops from 4 peritoneal sheets, which continue from gastrocolic ligament and, freely hanging down, covers the abdominal organs in front. The gastrocolic ligament connects the transverse colon with the greater curvature of the stomach.
Inferior floor of peritoneal cavity extends from mesocolon of transverse colon to entrance into lesser pelvis.
Root of small intestine mesentery divides the inferior storey into right and left mesenteric sinuses. They accommodate the loops of small intestine. Right mesenteric sinus is bordered by mesenteric root and ascending colon. In place, where ileum continues into cecum superior and inferior ileocecal recesses are situated. One can see retrocecal recess behind cecum. Right paracolic sulcus runs between ascending colon and parietal peritoneum of lateral abdominal wall. Mesenteric root, descending colon and sigmoid colon border left mesenteric sinus. Superior and inferior duodenal recesses are positioned in area of duodenojejunal junction. Mesocolon of sigmoid forms intersigmoidal recess. Left paracolic sulcus runs between descending colon and parietal peritoneum of left abdominal wall.
Parietal sheet of peritoneum covering back surface of anterior abdominal form plicae (folds) and fossae. The median umbilical fold contains the remnant of the embryonic urachus; the medial umbilical folds carry obliterated umbililal arteries; lateral umbilical folds contain inferior epigastric arteries. Supravesical fossae positioned between median and medial umbilical folds. Medial umbilical fossae located between medial and lateral umbilical folds. Lateral umbilical fossae located laterally from lateral umbilical folds. Medial and lateral umbilical fossae can be projected into superficial inguinal ring and deep inguinal ring.
Posterior view of the anterior abdominal wall in its lower half. The peritoneum is in place, and the various cords are shining through
Cavity of lesser pelvis
Peritoneal cavity in the male pelvis
contains rectovesical excavation (pouch). Peritoneum in the female
between uterus and urinary bladder form vesicouterinae excavation.
Behind the uterus peritoneum descends into the rectouterine pouch (pouch
Douglas), which is the lowest point of the
peritoneal cavity. That is why some liquid from all peritoneal cavity can
collect here during some pathology. The entrance into the rectouterine pouch is
narrowed by the rectouterine folds, in which the rectouterine muscles
Theme 3. Anatomy of the respiratory system.
The respiratory apparatus consists of the nose, nasal cavity, larynx, trachea, bronchi, lungs, and pleura.
External nose and the nasal cavity, which is divided by a septum into right and left nasal chambers.
External Nose (Nasus Externus; Outer Nose) is pyramidal in form, and its upper angle or root is connected directly with the forehead; its free angle is termed the apex. Its base is perforated by two elliptical orifices, the nares, separated from each other by an antero-posterior septum, the columna. The margins of the nares are provided with a number of stiff hairs, or vibrissæ, which arrest the passage of foreign substances carried with the current of air intended for respiration. The lateral surfaces of the nose form, by their union in the middle line, the dorsum nasi, the direction of which varies considerably in different individuals; the upper part of the dorsum is supported by the nasal bones, and is named the bridge. The lateral surface ends below in a rounded eminence, the ala nasi.
Structure.—The frame-work of the external nose is composed of bones and cartilages; it is covered by the integument, and lined by mucous membrane.
The bony frame-work occupies the upper part of the organ; it consists of the nasal bones, and the frontal processes of the maxillæ.
The cartilaginous frame-work (cartilagines nasi) consists of five large pieces, viz., the cartilage of the septum, the two lateral and the two greater alar cartilages, and several smaller pieces, the lesser alar cartilages. The various cartilages are connected to each other and to the bones by a tough fibrous membrane.
The cartilage of the septum (cartilago septi nasi) is somewhat quadrilateral in form, thicker at its margins than at its center, and completes the separation between the nasal cavities in front. Its anterior margin, thickest above, is connected with the nasal bones, and is continuous with the anterior margins of the lateral cartilages; below, it is connected to the medial crura of the greater alar cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular plate of the ethmoid; its inferior margin with the vomer and the palatine processes of the maxillæ.
It may be prolonged backward (especially in children) as a narrow process, the sphenoidal process, for some distance between the vomer and perpendicular plate of the ethmoid. The septal cartilage does not reach as far as the lowest part of the nasal septum. This is formed by the medial crura of the greater alar cartilages and by the skin; it is freely movable, and hence is termed the septum mobile nasi.
The lateral cartilage (cartilago nasi lateralis; upper lateral cartilage) is situated below the inferior margin of the nasal bone, and is flattened, and triangular in shape. Its anterior margin is thicker than the posterior, and is continuous above with the cartilage of the septum, but separated from it below by a narrow fissure; its superior margin is attached to the nasal bone and the frontal process of the maxilla; its inferior margin is connected by fibrous tissue with the greater alar cartilage.
The greater alar cartilage (cartilago alaris major; lower lateral cartilage) is a thin, flexible plate, situated immediately below the preceding, and bent upon itself in such a manner as to form the medial and lateral walls of the naris of its own side. The portion which forms the medial wall (crus mediale) is loosely connected with the corresponding portion of the opposite cartilage, the two forming, together with the thickened integument and subjacent tissue, the septum mobile nasi. The part which forms the lateral wall (crus laterale) is curved to correspond with the ala of the nose; it is oval and flattened, narrow behind, where it is connected with the frontal process of the maxilla by a tough fibrous membrane, in which are found three or four small cartilaginous plates, the lesser alar cartilages (cartilagines alares minores; sesamoid cartilages). Above, it is connected by fibrous tissue to the lateral cartilage and front part of the cartilage of the septum; below, it falls short of the margin of the naris, the ala being completed by fatty and fibrous tissue covered by skin. In front, the greater alar cartilages are separated by a notch which corresponds with the apex of the nose.
The muscles acting on the external nose have been described in the section on Myology.
The integument of the dorsum and sides of the nose is thin, and loosely connected with the subjacent parts; but over the tip and alæ it is thicker and more firmly adherent, and is furnished with a large number of sebaceous follicles, the orifices of which are usually very distinct.
The arteries of the external nose are the alar and septal branches of the external maxillary, which supply the alæ and septum; the dorsum and sides being supplied from the dorsal nasal branch of the ophthalmic and the infraorbital branch of the internal maxillary. The veins end in the anterior facial and ophthalmic veins.
The nerves for the muscles of the nose are derived from the facial, while the skin receives branches from the infratrochlear and nasociliary branches of the ophthalmic, and from the infraorbital of the maxillary.
the Nasal Cavity (Cavum Nasi; Nasal Fossa)—The
nasal chambers are situated one on either side of the median plane. They open
in front through the nares, and communicate behind through the choanæ
with the nasal part of the pharynx. The nares are somewhat pear-shaped
apertures, each measuring about
For the description of the bony boundaries of the nasal cavities, see pages 194 and 195.
Inside the aperture of the nostril is a slight dilatation, the vestibule, bounded laterally by the ala and lateral crus of the greater alar cartilage, and medially by the medial crus of the same cartilage. It is lined by skin containing hairs and sebaceous glands, and extends as a small recess toward the apex of the nose. Each nasal cavity, above and behind the vestibule, is divided into two parts: an olfactory region, consisting of the superior nasal concha and the opposed part of the septum, and a respiratory region, which comprises the rest of the cavity.
Lateral wall of nasal cavity.
Lateral Wall—On the lateral wall are the superior, middle, and inferior nasal conchæ, and below and lateral to each concha is the corresponding nasal passage or meatus. Above the superior concha is a narrow recess, the sphenoethmoidal recess, into which the sphenoidal sinus opens. The superior meatus is a short oblique passage extending about half-way along the upper border of the middle concha; the posterior ethmoidal cells open into the front part of this meatus. The middle meatus is below and lateral to the middle concha, and is continued anteriorly into a shallow depression, situated above the vestibule and named the atrium of the middle meatus. On raising or removing the middle concha the lateral wall of this meatus is fully displayed. On it is a rounded elevation, the bulla ethmoidalis, and below and in front of this is a curved cleft, the hiatus semilunaris.
The bulla ethmoidalis is caused by the bulging of the middle ethmoidal cells which open on or immediately above it, and the size of the bulla varies with that of its contained cells.
Lateral wall of nasal cavity; the three nasal conchæ have been removed.
The hiatus semilunaris is bounded inferiorly by the sharp concave margin of the uncinate process of the ethmoid bone, and leads into a curved channel, the infundibulum, bounded above by the bulla ethmoidalis and below by the lateral surface of the uncinate process of the ethmoid. The anterior ethmoidal cells open into the front part of the infundibulum, and this in slightly over 50 per cent. of subjects is directly continuous with the frontonasal duct or passage leading from the frontal air sinus; but when the anterior end of the uncinate process fuses with the front part of the bulla, this continuity is interrupted and the frontonasal duct then opens directly into the anterior end of the middle meatus.
Below the bulla ethmoidalis, and partly hidden by the inferior end of the uncinate process, is the ostium maxillare, or opening from the maxillary sinus; in a frontal section this opening is seen to be placed near the roof of the sinus. An accessory opening from the sinus is frequently present below the posterior end of the middle nasal concha. The inferior meatus is below and lateral to the inferior nasal concha; the nasolacrimal duct opens into this meatus under cover of the anterior part of the inferior concha.
Medial Wall or septum is frequently more or less deflected from the median plane, thus lessening the size of one nasal cavity and increasing that of the other; ridges or spurs of bone growing into one or other cavity from the septum are also sometimes present. Immediately over the incisive canal at the lower edge of the cartilage of the septum a depression, the nasopalatine recess, is seen. In the septum close to this recess a minute orifice may be discerned; it leads backward into a blind pouch, the rudimentary vomeronasal organ of Jacobson, which is supported by a strip of cartilage, the vomeronasal cartilage. This organ is well-developed in many of the lower animals, where it apparently plays a part in the sense of smell, since it is supplied by twigs of the olfactory nerve and lined by epithelium similar to that in the olfactory region of the nose.
The roof of the nasal cavity is narrow from side to side, except at its posterior part, and may be divided, from behind forward, into sphenoidal, ethmoidal, and frontonasal parts, after the bones which form it.
The floor is concave from side to side and almost horizontal antero-posteriorly; its anterior three-fourths are formed by the palatine process of the maxilla, its posterior fourth by the horizontal process of the palatine bone. In its anteromedial part, directly over the incisive foramen, a small depression, the nasopalatine recess, is sometimes seen; it points downward and forward and occupies the position of a canal which connected the nasal with the buccal cavity in early fetal life.
The Mucous Membrane (membrana mucosa nasi).—The nasal mucous membrane lines the nasal cavities, and is intimately adherent to the periosteum or perichondrium. It is continuous with the skin through the nares, and with the mucous membrane of the nasal part of the pharynx through the choanæ. From the nasal cavity its continuity with the conjunctiva may be traced, through the nasolacrimal and lacrimal ducts; and with the frontal, ethmoidal, sphenoidal, and maxillary sinuses, through the several openings in the meatuses. The mucous membrane is thickest, and most vascular, over the nasal conchæ. It is also thick over the septum; but it is very thin in the meatuses on the floor of the nasal cavities, and in the various sinuses.
Owing to the thickness of the greater part of this membrane, the nasal cavities are much narrower, and the middle and inferior nasal conchæ appear larger and more prominent than in the skeleton; also the various apertures communicating with the meatuses are considerably narrowed.
Structure of the Mucous Membrane. The epithelium covering the mucous membrane differs in its character according to the functions of the part of the nose in which it is found. In the respiratory region it is columnar and ciliated. Interspersed among the columnar cells are goblet or mucin cells, while between their bases are found smaller pyramidal cells. Beneath the epithelium and its basement membrane is a fibrous layer infiltrated with lymph corpuscles, so as to form in many parts a diffuse adenoid tissue, and under this a nearly continuous layer of small and larger glands, some mucous and some serous, the ducts of which open upon the surface. In the olfactory region the mucous membrane is yellowish in color and the epithelial cells are columnar and non-ciliated; they are of two kinds, supporting cells and olfactory cells. The supporting cells contain oval nuclei, which are situated in the deeper parts of the cells and constitute the zone of oval nuclei; the superficial part of each cell is columnar, and contains granules of yellow pigment, while its deep part is prolonged as a delicate process which ramifies and communicates with similar processes from neighboring cells, so as to form a net-work in the mucous membrane. Lying between the deep processes of the supporting cells are a number of bipolar nerve cells, the olfactory cells, each consisting of a small amount of granular protoplasm with a large spherical nucleus, and possessing two processes—a superficial one which runs between the columnar epithelial cells, and projects on the surface of the mucous membrane as a fine, hair-like process, the olfactory hair; the other or deep process runs inward, is frequently beaded, and is continued as the axon of an olfactory nerve fiber. Beneath the epithelium, and extending through the thickness of the mucous membrane, is a layer of tubular, often branched, glands, the glands of Bowman, identical in structure with serous glands. The epithelial cells of the nose, fauces and respiratory passages play an important role in the maintenance of an equable temperature, by the moisture with which they keep the surface always slightly lubricated.
Vessels and Nerves.—The arteries of the nasal cavities are the anterior and posterior ethmoidal branches of the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the nose; the sphenopalatine branch of the $$$ which supplies the mucous membrane covering the conchæ, the meatuses and septum, the septal branch of the superior labial of the external maxillary; the infraorbital and alveolar branches of the internal maxillary, which supply the lining membrane of the maxillary sinus; and the pharyngeal branch of the same artery, distributed to the sphenoidal sinus. The ramifications of these vessels form a close plexiform net-work, beneath and in the substance of the mucous membrane.
The veins form a close cavernous plexus beneath the mucous membrane. This plexus is especially well-marked over the lower part of the septum and over the middle and inferior conchæ. Some of the veins open into the sphenopalatine vein; others join the anterior facial vein; some accompany the ethmoidal arteries, and end in the ophthalmic veins; and, lastly, a few communicate with the veins on the orbital surface of the frontal lobe of the brain, through the foramina in the cribriform plate of the ethmoid bone; when the foramen cecum is patent it transmits a vein to the superior sagittal sinus.
The lymphatics have already been described.
The nerves of ordinary sensation are: the nasociliary branch of the ophthalmic, filaments from the anterior alveolar branch of the maxillary, the nerve of the pterygoid canal, the nasopalatine, the anterior palatine, and nasal branches of the sphenopalatine ganglion.
The nasociliary branch of the ophthalmic distributes filaments to the forepart of the septum and lateral wall of the nasal cavity. Filaments from the anterior alveolar nerve supply the inferior meatus and inferior concha. The nerve of the pterygoid canal supplies the upper and back part of the septum, and superior concha; and the upper nasal branches from the sphenopalatine ganglion have a similar distribution. The nasopalatine nerve supplies the middle of the septum. The anterior palatine nerve supplies the lower nasal branches to the middle and inferior conchæ.
The olfactory, the special nerve of the sense of smell, is distributed to the olfactory region. Its fibers arise from the bipolar olfactory cells and are destitute of medullary sheaths. They unite in fasciculi which form a plexus beneath the mucous membrane and then ascend in grooves or canals in the ethmoid bone; they pass into the skull through the foramina in the cribriform plate of the ethmoid and enter the under surface of the olfactory bulb, in which they ramify and form synapses with the dendrites of the mitral cells.
The Accessory Sinuses of the Nose (Sinus Paranasales)
The accessory sinuses or air cells of the nose are the frontal, ethmoidal, sphenoidal, and maxillary; they vary in size and form in different individuals, and are lined by ciliated mucous membrane directly continuous with that of the nasal cavities.
The Frontal Sinuses (sinus frontales),
situated behind the superciliary arches, are rarely symmetrical, and the septum
between them frequently deviates to one or other side of the middle line. Their
average measurements are as follows: height,
The Ethmoidal Air Cells (cellulæ ethmoidales) consist of numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine. They lie between the upper parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony laminæ. On either side they are arranged in three groups, anterior, middle, and posterior. The anterior and middle groups open into the middle meatus of the nose, the former by way of the infundibulum, the latter on or above the bulla ethmoidalis. The posterior cells open into the superior meatus under cover of the superior nasal concha; sometimes one or more opens into the sphenoidal sinus. The ethmoidal cells begin to develop during fetal life.
The Sphenoidal Sinuses (sinus sphenoidales)
contained within the body of the sphenoid vary in size and shape; owing to the
lateral displacement of the intervening septum they are rarely symmetrical. The
following are their average measurements: vertical height,
Specimen from a child eight days old. By sagittal sections removing the lateral portion of frontal bone, lamina papyracea of ethmoid, and lateral portion of maxilla—the sinus maxillaris, cellulæ ethmoidales, anterior and posterior,
The Maxillary Sinus (sinus maxillaris; antrum of
Highmore), the largest of the accessory sinuses of the nose, is a pyramidal
cavity in the body of the maxilla. Its base is formed by the lateral wall of
the nasal cavity, and its apex extends into the zygomatic process. Its roof or
orbital wall is frequently ridged by the infra-orbital canal, while its floor
is formed by the alveolar process and is usually 1/2 to
Specimen from a child eight years, eight months, and one day old. Lateral view of frontal, ethmoidal and maxillary sinus areas, the lateral portion of each having been removed by sagittal cuts. Note that the sinus frontalis developed directly from the infundibulum ethmoidale. Note also the incomplete septa in the sinus maxillaris.
The Larynx is situated in anterior neck area on level IV-VI cervical vertebrae. At the front infrahyoid muscles of neck cover it. Vessels and nervous bundles and lobes of thyroid gland lie from sides of larynx. Laryngeal part of pharynx adjoins behind it.
Larynx skeleton consists of pair and odd cartilages.
• Thyroid cartilage, which consists of right and left plates (lamina dextra et sinistra), and also has superior horns and inferior horns; the plates converge forming laryngeal prominence (Adam’s apple);
• Cricoid cartilage which has anteriorly arch behind - plate of cricoid cartilage;
• Epiglottis cartilage.
The cartilages of the larynx. Posterior view.
• Arytenoid cartilage, which has a base and apex, muscular process and vocal process. These cartilage lie on plate of cricoid cartilage;
• Corniculate cartilage lies in aryepiglottic fold on top of arytenoid cartilages;
• Cuneiform cartilage lies in aryepiglottic fold front of corniculate cartilages.
In larynx they distinguish such articulations:
• Cricoid-thyroid joint is between inferior cornu of thyroid cartilage and arch of cricoid cartilage; in this joint movement is possible around transversal axis;
• Cricoid-arytenoid joint is situated between base of arytenoid cartilages and plate of cricoid cartilage. Arytenoid cartilage can rotate slide to meet one another.
Ligaments of the larynx:
• Thyro-hyoid membrane, which hangs larynx to hyoid bone;
• Crico-thyroid ligament;
• Thyro-epiglottic ligament;
• Hyoepiglottic ligament;
• Vestibular ligaments, which are situated over vocal ligaments.
The ligaments of the larynx. Antero-lateral view.
Fibroelastic membrane the larynx:
· Elastic cone contains in its superior margin vocal ligament;
· Quadrangular membrane, which is situated over elastic cone and in its inferior margin contains vestibular ligament.
Fibroelastic membranes together with laryngeal cartilages form a laryngeal skeleton.
The laryngeal Muscles subdivide on muscles that narrow/broaden the glottis, muscles that change tension of vocal ligament.
Constrictors of the glottis:
· lateral cricoarytenoid muscle;
· thyroarytenoid muscle;
· transverse arytenoid muscle;
· oblique arytenoid muscles.
Muscles-dilators of the glottis
• thyro-arytenoid muscle has thyro-epiglottic part. Action: it raises the epiglottis and broadens an entrance into larynx and vestibule.
• posterior cricoid-arytenoid muscle.
Muscles changing tension of vocal ligament:
• crico-thyroid muscle stretches a vocal ligament.
• vocal muscle is situated in thickness of vocal fold and changes an tension degree of vocal cords.
Laryngeal cavity has aditus laryngis [entrance], vestibule, interventricular space, glottis and infraglottic cavity.
Larynx has true vocal folds and glottis. Larynx begins by entrance into larynx, which is limited at the front, by epiglottis, behind – by arytenoid cartilages, and laterally - by arytenoepiglottic folds, where cuneiform and corniculate tubercles are situated (places of the same name cartilages). Glottis is a most narrow place in laryngeal cavity; it is situated between right and left vocal plicae. Laryngeal ventricle is fissure disposed between vocal and vestibular plicae.
Infraglottic cavity is inferior broadened part of larynx, which continues into trachea.
The larynx or organ of voice is placed at the upper part of the air passage. It is situated between the trachea and the root of the tongue, at the upper and forepart of the neck, where it presents a considerable projection in the middle line. It forms the lower part of the anterior wall of the pharynx, and is covered behind by the mucous lining of that cavity; on either side of it lie the great vessels of the neck. Its vertical extent corresponds to the fourth, fifth, and sixth cervical vertebræ, but it is placed somewhat higher in the female and also during childhood. Symington found that in infants between six and twelve months of age the tip of the epiglottis was a little above the level of the fibrocartilage between the odontoid process and body of the axis, and that between infancy and adult life the larynx descends for a distance equal to two vertebral bodies and two intervertebral fibrocartilages. According to Sappey the average measurements of the adult larynx are as follows:
Until puberty the larynx of the male differs little in size from that of the female. In the female its increase after puberty is only slight; in the male it undergoes considerable increase; all the cartilages are enlarged and the thyroid cartilage becomes prominent in the middle line of the neck, while the length of the rima glottidis is nearly doubled.
The larynx is broad above, where it presents the form of a triangular box flattened behind and at the sides, and bounded in front by a prominent vertical ridge. Below, it is narrow and cylindrical. It is composed of cartilages, which are connected together by ligaments and moved by numerous muscles. It is lined by mucous membrane continuous above with that of the pharynx and below with that of the trachea.
The Cartilages of the Larynx (cartilagines laryngis) are nine in number, three single and three paired, as follows:
Two Cuneiform. Epiglottis
The Thyroid Cartilage (cartilago thyreoidea) is the largest cartilage of the larynx. It consists of two laminæ the anterior borders of which are fused with each other at an acute angle in the middle line of the neck, and form a subcutaneous projection named the laryngeal prominence (pomum Adami). This prominence is most distinct at its upper part, and is larger in the male than in the female. Immediately above it the laminæ are separated by a V-shaped notch, the superior thyroid notch. The laminæ are irregularly quadrilateral in shape, and their posterior angles are prolonged into processes termed the superior and inferior cornua.
The outer surface of each lamina presents an oblique line which runs downward and forward from the superior thyroid tubercle situated near the root of the superior cornu, to the inferior thyroid tubercle on the lower border. This line gives attachment to the Sternothyreoideus, Thyreohyoideus, and Constrictor pharyngis inferior.
The inner surface is smooth; above and behind, it is slightly concave and covered by mucous membrane. In front, in the angle formed by the junction of the laminæ, are attached the stem of the epiglottis, the ventricular and vocal ligaments, the Thyreoarytænoidei, Thyreoepiglottici and Vocales muscles, and the thyroepiglottic ligament.
The upper border is concave behind and convex in front; it gives attachment to the corresponding half of the hyothyroid membrane.
The lower border is concave behind, and nearly straight in front, the two parts being separated by the inferior thyroid tubercle. A small part of it in and near the middle line is connected to the cricoid cartilage by the middle cricothyroid ligament.
The posterior border, thick and rounded, receives the insertions of the Stylopharyngeus and Pharyngopalatinus. It ends above, in the superior cornu, and below, in the inferior cornu. The superior cornu is long and narrow, directed upward, backward, and medialward, and ends in a conical extremity, which gives attachment to the lateral hyothyroid ligament. The inferior cornu is short and thick; it is directed downward, with a slight inclination forward and medialward, and presents, on the medial side of its tip, a small oval articular facet for articulation with the side of the cricoid cartilage.
During infancy the laminæ of the thyroid cartilage are joined to each other by a narrow, lozenge-shaped strip, named the intrathyroid cartilage. This strip extends from the upper to the lower border of the cartilage in the middle line, and is distinguished from the laminæ by being more transparent and more flexible.
The Cricoid Cartilage (cartilago cricoidea) is smaller, but thicker and stronger than the thyroid, and forms the lower and posterior parts of the wall of the larynx. It consists of two parts: a posterior quadrate lamina, and a narrow anterior arch, one-fourth or one-fifth of the depth of the lamina.
The lamina (lamina cartilaginis cricoideæ; posterior
portion) is deep and broad, and measures from above downward about 2 or
The arch (arcus cartilaginis cricoideæ; anterior portion)
is narrow and convex, and measures vertically from 5 to
On either side, at the junction of the lamina with the arch, is a small round articular surface, for articulation with the inferior cornu of the thyroid cartilage.
The lower border of the cricoid cartilage is horizontal, and connected to the highest ring of the trachea by the cricotracheal ligament.
The upper border runs obliquely upward and backward, owing to the great depth of the lamina. It gives attachment, in front, to the middle cricothyroid ligament; at the side, to the conus elasticus and the Cricoarytænoidei laterales; behind, it presents, in the middle, a shallow notch, and on either side of this is a smooth, oval, convex surface, directed upward and lateralward, for articulation with the base of an arytenoid cartilage.
The inner surface of the cricoid cartilage is smooth, and lined by mucous membrane.
The Arytenoid Cartilages (cartilagines arytænoideæ) are two in number, and situated at the upper border of the lamina of the cricoid cartilage, at the back of the larynx. Each is pyramidal in form, and has three surfaces, a base, and an apex.
The posterior surface is a triangular, smooth, concave, and gives attachment to the Arytænoidei obliquus and transversus.
The antero-lateral surface is somewhat convex and rough. On it, near the apex of the cartilage, is a rounded elevation (colliculus) from which a ridge (crista arcuata) curves at first backward and then downward and forward to the vocal process. The lower part of this crest intervenes between two depressions or foveæ, an upper, triangular, and a lower oblong in shape; the latter gives attachment to the Vocalis muscle.
The medial surface is narrow, smooth, and flattened, covered by mucous membrane, and forms the lateral boundary of the intercartilaginous part of the rima glottidis.
The base of each cartilage is broad, and on it is a concave smooth surface, for articulation with the cricoid cartilage. Its lateral angle is short, rounded, and prominent; it projects backward and lateralward, and is termed the muscular process; it gives insertion to the Cricoarytænoideus posterior behind, and to the Cricoarytænoideus lateralis in front. Its anterior angle, also prominent, but more pointed, projects horizontally forward; it gives attachment to the vocal ligament, and is called the vocal process.
The apex of each cartilage is pointed, curved backward and medialward, and surmounted by a small conical, cartilaginous nodule, the corniculate cartilage.
The Corniculate Cartilages (cartilagines corniculatæ; cartilages of Santorini) are two small conical nodules consisting of yellow elastic cartilage, which articulate with the summits of the arytenoid cartilages and serve to prolong them backward and medialward. They are situated in the posterior parts of the aryepiglottic folds of mucous membrane, and are sometimes fused with the arytenoid cartilages.
The Cuneiform Cartilages (cartilagines cuneiformes; cartilages of Wrisberg) are two small, elongated pieces of yellow elastic cartilage, placed one on either side, in the aryepiglottic fold, where they give rise to small whitish elevations on the surface of the mucous membrane, just in front of the arytenoid cartilages.
The Epiglottis (cartilago epiglottica) is a thin lamella of fibrocartilage of a yellowish color, shaped like a leaf, and projecting obliquely upward behind the root of the tongue, in front of the entrance to the larynx. The free extremity is broad and rounded; the attached part or stem is long, narrow, and connected by the thyroepiglottic ligament to the angle formed by the two laminæ of the thyroid cartilage, a short distance below the superior thyroid notch. The lower part of its anterior surface is connected to the upper border of the body of the hyoid bone by an elastic ligamentous band, the hyoepiglottic ligament.
The anterior or lingual surface is curved forward, and covered on its upper, free part by mucous membrane which is reflected on to the sides and root of the tongue, forming a median and two lateral glossoepiglottic folds; the lateral folds are partly attached to the wall of the pharynx. The depressions between the epiglottis and the root of the tongue, on either side of the median fold, are named the valleculæ. The lower part of the anterior surface lies behind the hyoid bone, the hyothyroid membrane, and upper part of the thyroid cartilage, but is separated from these structures by a mass of fatty tissue.
The posterior or laryngeal surface is smooth, concave from side to side, concavo-convex from above downward; its lower part projects backward as an elevation, the tubercle or cushion. When the mucous membrane is removed, the surface of the cartilage is seen to be indented by a number of small pits, in which mucous glands are lodged. To its sides the aryepiglottic folds are attached.
Structure.—The corniculate and cuneiform cartilages, the epiglottis, and the apices of the arytenoids at first consist of hyaline cartilage, but later elastic fibers are deposited in the matrix, converting them into yellow fibrocartilage, which shows little tendency to calcification. The thyroid, cricoid, and the greater part of the arytenoids consist of hyaline cartilage, and become more or less ossified as age advances. Ossification commences about the twenty-fifth year in the thyroid cartilage, and somewhat later in the cricoid and arytenoids; by the sixty-fifth year these cartilages may be completely converted into bone.
Ligaments.—The ligaments of the larynxare extrinsic, i. e., those connecting the thyroid cartilage and epiglottis with the hyoid bone, and the cricoid cartilage with the trachea; and intrinsic, those which connect the several cartilages of the larynx to each other.
Extrinsic Ligaments.—The ligaments connecting the thyroid cartilage with the hyoid bone are the hyothyroid membrane, and a middle and two lateral hyothyroid ligaments.
The Hyothyroid Membrane (membrana hyothyreoidea; thyrohyoid membrane) is a broad, fibro-elastic layer, attached below to the upper border of the thyroid cartilage and to the front of its superior cornu, and above to the upper margin of the posterior surface of the body and greater cornua of the hyoid bone, thus passing behind the posterior surface of the body of the hyoid, and being separated from it by a mucous bursa, which facilitates the upward movement of the larynx during deglutition. Its middle thicker part is termed the middle hyothyroid ligament (ligamentum hyothyreoideum medium; middle thyrohyoid ligament), its lateral thinner portions are pierced by the superior laryngeal vessels and the internal branch of the superior laryngeal nerve. Its anterior surface is in relation with the Thyreohyoideus, Sternohyoideus, and Omohyoideus, and with the body of the hyoid bone.
The Lateral Hyothyroid Ligament (ligamentum hyothyreoideum laterale; lateral thyrohyoid ligament) is a round elastic cord, which forms the posterior border of the hyothyroid membrane and passes between the tip of the superior cornu of the thyroid cartilage and the extremity of the greater cornu of the hyoid bone. A small cartilaginous nodule (cartilago triticea), sometimes bony, is frequently found in it.
The Epiglottis is connected with the hyoid bone by an elastic band, the hyoepiglottic ligament (ligamentum hyoepiglotticum), which extends from the anterior surface of the epiglottis to the upper border of the body of the hyoid bone. The glossoepiglottic folds of mucous membrane (page 1075) may also be considered as extrinsic ligaments of the epiglottis.
The Cricotracheal Ligament (ligamentum cricotracheale) connects the cricoid cartilage with the first ring of the trachea. It resembles the fibrous membrane which connects the cartilaginous rings of the trachea to each other.
Intrinsic Ligaments.—Beneath the mucous membrane of the larynx is a broad sheet of fibrous tissue containing many elastic fibers, and termed the elastic membrane of the larynx. It is subdivided on either side by the interval between the ventricular and vocal ligaments, the upper portion extends between the arytenoid cartilage and the epiglottis and is often poorly defined; the lower part is a well-marked membrane forming, with its fellow of the opposite side, the conus elasticus which connects the thyroid, cricoid, and arytenoid cartilages to one another. In addition the joints between the individual cartilages are provided with ligaments.
The Conus Elasticus (cricothyroid membrane) is composed mainly of yellow elastic tissue. It consists of an anterior and two lateral portions. The anterior part or middle cricothyroid ligament (ligamentum cricothyreoideum medium; central part of cricothyroid membrane) is thick and strong, narrow above and broad below. It connects together the front parts of the contiguous margins of the thyroid and cricoid cartilages. It is overlapped on either side by the Cricothyreoideus, but between these is subcutaneous; it is crossed horizontally by a small anastomotic arterial arch, formed by the junction of the two cricothyroid arteries, branches of which pierce it. The lateral portions are thinner and lie close under the mucous membrane of the larynx; they extend from the superior border of the cricoid cartilage to the inferior margin of the vocal ligaments, with which they are continuous. These ligaments may therefore be regarded as the free borders of the lateral portions of the conus elasticus, and extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage about midway between its upper and lower borders.
An articular capsule, strengthened posteriorly by a well-marked fibrous band, encloses the articulation of the inferior cornu of the thyroid with the cricoid cartilage on either side.
Each arytenoid cartilage is connected to the cricoid by a capsule and a posterior cricoarytenoid ligament. The capsule (capsula articularis cricoarytenoidea) is thin and loose, and is attached to the margins of the articular surfaces. The posterior cricoarytenoid ligament (ligamentum cricoarytenoideum posterius) extends from the cricoid to the medial and back part of the base of the arytenoid.
The thyroepiglottic ligament (ligamentum thyreoepiglotticum) is a long, slender, elastic cord which connects the stem of the epiglottis with the angle of the thyroid cartilage, immediately beneath the superior thyroid notch, above the attachment of the ventricular ligaments.
Movements.—The articulation between the inferior cornu of the thyroid cartilage and the cricoid cartilage on either side is a diarthrodial one, and permits of rotatory and gliding movements. The rotatory movement is one in which the cricoid cartilage rotates upon the inferior cornua of the thyroid cartilage around an axis passing transversely through both joints. The gliding movement consists in a limited shifting of the cricoid on the thyroid in different directions.
The articulation between the arytenoid cartilages and the cricoid is also a diarthrodial one, and permits of two varieties of movement: one is a rotation of the arytenoid on a vertical axis, whereby the vocal process is moved lateralward or medialward, and the rima glottidis increased or diminished; the other is a gliding movement, and allows the arytenoid cartilages to approach or recede from each other; from the direction and slope of the articular surfaces lateral gliding is accompanied by a forward and downward movement. The two movements of gliding and rotation are associated, the medial gliding being connected with medialward rotation, and the lateral gliding with lateralward rotation. The posterior cricoarytenoid ligaments limit the forward movement of the arytenoid cartilages on the cricoid.
Interior of the Larynx—The cavity of the larynx (cavum laryngis) extends from the laryngeal entrance to the lower border of the cricoid cartilage where it is continuous with that of the trachea. It is divided into two parts by the projection of the vocal folds, between which is a narrow triangular fissure or chink, the rima glottidis. The portion of the cavity of the larynx above the vocal folds is called the vestibule; it is wide and triangular in shape, its base or anterior wall presenting, however, about its center the backward projection of the tubercle of the epiglottis. It contains the ventricular folds, and between these and the vocal folds are the ventricles of the larynx. The portion below the vocal folds is at first of an elliptical form, but lower down it widens out, assumes a circular form, and is continuous with the tube of the trachea.
The entrance of the larynx is a triangular opening, wide in front, narrow behind, and sloping obliquely downward and backward. It is bounded, in front, by the epiglottis; behind, by the apices of the arytenoid cartilages, the corniculate cartilages, and the interarytenoid notch; and on either side, by a fold of mucous membrane, enclosing ligamentous and muscular fibers, stretched between the side of the epiglottis and the apex of the arytenoid cartilage; this is the aryepiglottic fold, on the posterior part of the margin of which the cuneiform cartilage forms a more or less distinct whitish prominence, the cuneiform tubercle.
The Ventricular Folds (plicœ ventriculares; superior or false vocal cords) are two thick folds of mucous membrane, each enclosing a narrow band of fibrous tissue, the ventricular ligament which is attached in front to the angle of the thyroid cartilage immediately below the attachment of the epiglottis, and behind to the antero-lateral surface of the arytenoid cartilage, a short distance above the vocal process. The lower border of this ligament, enclosed in mucous membrane, forms a free crescentic margin, which constitutes the upper boundary of the ventricle of the larynx.
The Vocal Folds (plicœ vocales; inferior or true vocal cords) are concerned in the production of sound, and enclose two strong bands, named the vocal ligaments (ligamenta vocales; inferior thyroarytenoid). Each ligament consists of a band of yellow elastic tissue, attached in front to the angle of the thyroid cartilage, and behind to the vocal process of the arytenoid. Its lower border is continuous with the thin lateral part of the conus elasticus. Its upper border forms the lower boundary of the ventricle of the larynx. Laterally, the Vocalis muscle lies parallel with it. It is covered medially by mucous membrane, which is extremely thin and closely adherent to its surface.
The Ventricle of the Larynx (ventriculus laryngis [Morgagnii]; laryngeal sinus) is a fusiform fossa, situated between the ventricular and vocal folds on either side, and extending nearly their entire length. The fossa is bounded, above, by the free crescentic edge of the ventricular fold; below, by the straight margin of the vocal fold; laterally, by the mucous membrane covering the corresponding Thyreoarytænoideus. The anterior part of the ventricle leads up by a narrow opening into a cecal pouch of mucous membrane of variable size called the appendix.
The appendix of the laryngeal ventricle (appendix ventriculi laryngis; laryngeal saccule) is a membranous sac, placed between the ventricular fold and the inner surface of the thyroid cartilage, occasionally extending as far as its upper border or even higher; it is conical in form, and curved slightly backward. On the surface of its mucous membrane are the openings of sixty or seventy mucous glands, which are lodged in the submucous areolar tissue. This sac is enclosed in a fibrous capsule, continuous below with the ventricular ligament. Its medial surface is covered by a few delicate muscular fasciculi, which arise from the apex of the arytenoid cartilage and become lost in the aryepiglottic fold of mucous membrane; laterally it is separated from the thyroid cartilage by the Thyreoepiglotticus. These muscles compress the sac, and express the secretion it contains upon the vocal folds to lubricate their surfaces.
The Rima Glottidis is the elongated fissure or chink between the
vocal folds in front, and the bases and vocal processes of the arytenoid
cartilages behind. It is therefore subdivided into a larger anterior
intramembranous part (glottis vocalis), which measures about
three-fifths of the length of the entire aperture, and a posterior
intercartilaginous part (glottis respiratoria). Posteriorly it is
limited by the mucous membrane passing between the arytenoid cartilages. The
rima glottidis is the narrowest part of the cavity of the larynx, and its level
corresponds with the bases of the arytenoid cartilages. Its length, in the
male, is about
Muscles.—The muscles of the larynx are extrinsic, passing between the larynx and parts around—these have been described in the section on Myology; and intrinsic, confined entirely to the larynx.
The intrinsic muscles are:
The Cricothyreoideus (Cricothyroid) Triangular in form, arises from the front and lateral part of the cricoid cartilage; its fibers diverge, and are arranged in two groups. The lower fibers constitute a pars obliqua and slant backward and lateralward to the anterior border of the inferior cornu; the anterior fibers, forming a pars recta, run upward, backward, and lateralward to the posterior part of the lower border of the lamina of the thyroid cartilage.
The medial borders of the two muscles are separated by a triangular interval, occupied by the middle cricothyroid ligament.
The Cricoarytænoideus posterior (posterior cricoarytenoid) (Fig. 958) arises from the broad depression on the corresponding half of the posterior surface of the lamina of the cricoid cartilage; its fibers run upward and lateralward, and converge to be inserted into the back of the muscular process of the arytenoid cartilage. The uppermost fibers are nearly horizontal, the middle oblique, and the lowest almost vertical.
The Cricoarytænoideus lateralis (lateral cricoarytenoid) (Fig. 959) is smaller than the preceding, and of an oblong form. It arises from the upper border of the arch of the cricoid cartilage, and, passing obliquely upward and backward, is inserted into the front of the muscular process of the arytenoid cartilage.
Muscles of larynx. Side view. Right lamina of thyroid cartilage removed.
The Arytænoideus is a single muscle, filling up the posterior concave surfaces of the arytenoid cartilages. It arises from the posterior surface and lateral border of one arytenoid cartilage, and is inserted into the corresponding parts of the opposite cartilage. It consists of oblique and transverse parts. The Arytænoideus obliquus, the more superficial, forms two fasciculi, which pass from the base of one cartilage to the apex of the opposite one, and therefore cross each other like the limbs of the letter X; a few fibers are continued around the lateral margin of the cartilage, and are prolonged into the aryepiglottic fold; they are sometimes described as a separate muscle, the Aryepiglotticus. The Arytænoideus transversus crosses transversely between the two cartilages.
The Thyreoarytænoideus (Thyroarytenoid) is a broad, thin, muscle which lies parallel with and lateral to the vocal fold, and supports the wall of the ventricle and its appendix. It arises in front from the lower half of the angle of the thyroid cartilage, and from the middle cricothyroid ligament. Its fibers pass backward and lateralward, to be inserted into the base and anterior surface of the arytenoid cartilage. The lower and deeper fibers of the muscle can be differentiated as a triangular band which is inserted into the vocal process of the arytenoid cartilage, and into the adjacent portion of its anterior surface; it is termed the Vocalis, and lies parallel with the vocal ligament, to which it is adherent.
A considerable number of the fibers of the Thyreoarytænoideus are prolonged into the aryepiglottic fold, where some of them become lost, while others are continued to the margin of the epiglottis. They have received a distinctive name, Thyreoepiglotticus, and are sometimes described as a separate muscle. A few fibers extend along the wall of the ventricle from the lateral wall of the arytenoid cartilage to the side of the epiglottis and constitute the Ventricularis muscle.
Actions.—In considering the actions of the muscles of the larynx, they may be conveniently divided into two groups, vix.: 1. Those which open and close the glottis. 2. Those which regulate the degree of tension of the vocal folds.
The Cricoarytœnoidei posteriores separate the vocal folds, and, consequently, open the glottis, by rotating the arytenoid cartilages outward around a vertical axis passing through the cricoarytenoid joints; so that their vocal processes and the vocal folds attached to them become widely separated.
The Cricoarytœnoidei laterales close the glottis by rotating the arytenoid cartilages inward, so as to approximate their vocal processes.
The Arytœnoideus approximates the arytenoid cartilages, and thus closes the opening of the glottis, especially at its back part.
The Cricothyreoidei produce tension and elongation of the vocal folds by drawing up the arch of the cricoid cartilage and tilting back the upper border of its lamina; the distance between the vocal processes and the angle of the thyroid is thus increased, and the folds are consequently elongated.
The Thyreoarytœnoidei, consisting of two parts having different attachments and different directions, are rather complicated as regards their action. Their main use is to draw the arytenoid cartilages forward toward the thyroid, and thus shorten and relax the vocal folds. But, owing to the connection of the deeper portion with the vocal fold, this part, if acting separately, is supposed to modify its elasticity and tension, while the lateral portion rotates the arytenoid cartilage inward, and thus narrows the rima glottidis by bringing the two vocal folds together.
Mucous Membrane.—The mucous membrane of the larynx is continuous above with that lining the mouth and pharynx, and is prolonged through the trachea and bronchi into the lungs. It lines the posterior surface and the upper part of the anterior surface of the epiglottis, to which it is closely adherent, and forms the aryepiglottic folds which bound the entrance of the larynx. It lines the whole of the cavity of the larynx; forms, by its reduplication, the chief part of the ventricular fold, and, from the ventricle, is continued into the ventricular appendix. It is then reflected over the vocal ligament, where it is thin, and very intimately adherent; covers the inner surface of the conus elasticus and cricoid cartilage; and is ultimately continuous with the lining membrane of the trachea. The anterior surface and the upper half of the posterior surface of the epiglottis, the upper part of the aryepiglottic folds and the vocal folds are covered by stratified squamous epithelium; all the rest of the laryngeal mucous membrane is covered by columnar ciliated cells, but patches of stratified squamous epithelium are found in the mucous membrane above the glottis.
Glands.—The mucous membrane of the larynx is furnished with numerous mucous secreting glands, the orifices of which are found in nearly every part; they are very plentiful upon the epiglottis, being lodged in little pits in its substance; they are also found in large numbers along the margin of the aryepiglottic fold, in front of the arytenoid cartilages, where they are termed the arytenoid glands. They exist also in large numbers in the ventricular appendages. None are found on the free edges of the vocal folds.
Vessels and Nerves.—The chief arteries of the larynx are the laryngeal branches derived from the superior and inferior thyroid. The veins accompany the arteries; those accompanying the superior laryngeal artery join the superior thyroid vein which opens into the internal jugular vein; while those accompanying the inferior laryngeal artery join the inferior thyroid vein which opens into the innominate vein. The lymphatic vessels consist of two sets, superior and inferior. The former accompany the superior laryngeal artery and pierce the hyothyroid membrane, to end in the glands situated near the bifurcation of the common carotid artery. Of the latter, some pass through the middle cricothyroid ligament and open into a gland lying in front of that ligament or in front of the upper part of the trachea, while others pass to the deep cervical glands and to the glands accompanying the inferior thyroid artery. The nerves are derived from the internal and external branches of the superior laryngeal nerve, from the recurrent nerve, and from the sympathetic. The internal laryngeal branch is almost entirely sensory, but some motor filaments are said to be carried by it to the Arytænoideus. It enters the larynx by piercing the posterior part of the hyothyroid membrane above the superior laryngeal vessels, and divides into a branch which is distributed to both surfaces of the epiglottis, a second to the aryepiglottic fold, and a third, the largest, which supplies the mucous membrane over the back of the larynx and communicates with the recurrent nerve. The external laryngeal branch supplies the Cricothyreoideus. The recurrent nerve passes upward beneath the lower border of the Constrictor pharyngis inferior immediately behind the cricothyroid joint. It supplies all the muscles of the larynx except the Cricothyreoideus, and perhaps a part of the Arytænoideus. The sensory branches of the laryngeal nerves form subepithelial plexuses, from which fibers pass to end between the cells covering the mucous membrane.
Over the posterior surface of the epiglottis, in the aryepiglottic folds, and less regularly in some other parts, taste-buds, similar to those in the tongue, are found.
The TRACHEA is a tube, which consists of 16-20 semicircular cartilages, joint each other by annular ligaments. Last built by connective tissue with smooth muscular fibres. Behind semi-rings communicate by each other by membranous tracheal wall. Trachea (windpipe) extends from VI cervical to V thoracic vertebra, where it ramifies on two principal bronchi. This place is tracheal bifurcation. Trachea has cervical part and thoracic part. Cervical part at the front covered by infrahyoid muscles and isthmus of thyroid gland that accords to the second-third tracheal ring. Esophagus (gullet) passes behind the trachea. Thoracic part of trachea is situated in superior mediastinum.
Front view of cartilages of larynx, trachea
PRINCIPAL BRONCHI are generated from the bifurcation of trachea and have similar structure as trachea. Right principal bronchus is wider than left and it is continuation of trachea by its direction. It consists of 6-8 cartilaginous semirings. Left principal bronchus is longer and narrower and passes with angle from trachea than right. It consists of 9-12 cartilaginous semi-ring. The principal bronchi are the bronchi of first order, the bronchial tree starts from them. The extraneous things, especially in children, more frequently get into right principal bronchus.
Transverse section of the trachea, just above its bifurcation, with a bird’s-eye view of the interior.
The LUNGS are the pair parenchymatic organs, which occupy larger part of thoracic cavity. Each lung has a pulmonal base and apex; costal surface, diaphragmatic surface, interlobar surface and medial surface. Medial surface subdivides into posterior (vertebral) surface and anterior (mediastinal) surface. They distinguish anterior margin and inferior margin on lungs. There is pulmonal hilus on mediastinal surface through which pulmonary artery, bronchi and nerves, enter into the lung, lymphatic vessels and pulmonary veins leave the lungs. All these elements, which enter and exite from lungs gates, form a pulmonary root. Arrangement of vessels and bronchus in left pulmonary root: from above downwards: pulmonary artery, bronchus and vein (АВV). Arrangement of vessels and bronchus in right pulmonary root (from above downwards): bronchus, pulmonary artery, and vein (BAV). On lateral surface of lungs oblique fissura passes, which subdivides each lung into superior lobe and inferior lobe.
Right lungs, except oblique fissure, has a horizontal fissure passes on level of the IV ribs, which separates middle and inferior lobes of the right lung. Left lung is more narrow and longer than right one and in area of anterior margin it has cardiac notch of left lung, limited from below by uvula. The principal bronchi, turning into lung gates, subdivide into bronchi of second order, which ventilate lung lobes (lobar bronchi). There are 2 lobar bronchi in left lung, and 3 - in right lung. The lobar bronchi subdivide into bronchi of third order, which ventilate lung area, dissociated from neighboring by stratum of connective tissue, which is called as lung segment. That's why these bronchi are called as by segmental bronchi. According to San Paulo nomenclature in superior lobe of right lung situated 3 segments, in middle - 2, and in inferior 5 segments; in right lung they count 10 segments. In superior lobe of left lung count 4 (or 5) segments, and in inferior lobe - 6 (or 5) segments. So, in left lung counts also 10 segments.
Segmental bronchi dichotomically (each on two) divides by bronchi of following orders, while do not pass as far as bronchi, which ventilate lung area, that has a volume 1мм3. This area is called by pulmonary lobule and bronchi, which ventilate it, are called lobular bronchi. Lesser bronchi contain more connective tissue in their wall and less cartilaginous tissue. From each lobular bronchus 16-18 terminal bronchiole start, their wall does not contain cartilaginous tissue. Bronchial tree includes branching of the bronchi starting from the principal bronchi and finishing by terminal bronchioli. Next branching of the bronchial tubes they call acynus – morpho-functional lung unit.
Acynus contains 14-16 respiratory bronchіoli, which are ramification of one terminal bronchіoli and they have alveoli in the wall. Each respiratory bronchі forms to 1500 alveolar ductuli, which terminate in alveolar saccule. One pulmonary lobule contains 16-18 acynuses. The acynus is covered by network of vessels. Gas-exchange between external environment and blood takes place here.
Parenchyma of the lungs and walls of thoracic cavity covered by serous membrane named pleura. Sheet of pleurae which covers the lung called visceral, and one which covers inner walls of thoracic cavity named parietal. Parietal pleura pass into visceral one in place of pulmonal ligament which lies in frontal plane. Parietal pleura divided into some portions: costal portion, diaphragmatic, mediastinal portion and has a cupola of pleurae.
Narrow fissure pleural cavity contains some serous liquid situated between parietal and visceral pleurae. In areas, where one part of parietal pleurae continues into other, recesses form, into which lung deepens during taking a deep breath. They distinguish a costodiaphragmatic recess (largest), diaphragmaticоmediastinal recess, vertebrоmediastinal recess and costomediastinal recess.
The MEDIASTINUM is complex of organs, which is situated between two pleural sacs. Mediastinum is limited - at front by sternum, behind by thoracic part of backbone, from sides - by right and left mediastinal pleurae. Its superior boundary is superior foramen of thoracic cavity, and inferior - diaphragm. Conventionally horizontal plane, carrying out from joint of manubrium sterni and corpus sterni to cartilage between IV-V thoracic vertebrae, divides mediastinum into superior mediastinum and inferior mediastinum.
In superior mediastinum thymus gland, superior cava vein, aortal arch, part of trachea, superior part of thoracic esophageal portion, suitable parts of thoracic lymphatic duct, sympathetic trunks, vagus and phrenic nerves are situated.
Inferior mediastinum into its
turn subdivides into anterior mediastinum, middle mediastinum and posterior
mediastinum. Anterior mediastinum is situated between body by sternum
and anterior wall of pericardium. Internal thoracic arteries and veins,
lymphatic nodes and vessels are situated here. On middle mediastinum
heart, covered by pericardium, phrenic nerves and inner pericardial portions of
big vessels are located. Posterior mediastinum is situated between
posterior pericardial wall and backbone. Thoracic part of aorta, azygos and
hemiazygos veins, sympathetic trunks, splanchnic nerves, vagus nerves,
esophagus, thoracic duct, lymphatic nodes passes here. Boundaries of LUNGs and PLEURAe. The superior border of lung
and pleura (pleura cupola) coincide and situated on 2-
Anterior lung boundary path also coincides with by anterior
pleural border. It passes from top of the lung to sternоclavicular joint,
passes over middle the manubrium sterni, sternal body from II to IV costal
cartilage. Anterior boundary of left lung deviates here to the left, passes on
parasternal line till VI rib, where continues into inferior border. Anterior
boundary path of right lung passes along the border of left lung, but gradually
deviates to the right and on level of the VI costal cartilage on right
parasternal line continues into inferior border. Inferior boundary path
of right lung is situated 1-
§ on medioclavicular line - at level of the VI ribs,
§ on anterior axillar line - on level of the VII ribs,
§ on middle axillar line - on level of the VIII ribs,
§ on posterior axillar line - on level of the IX ribs,
§ on scapular line - on level of the Х ribs,
§ on paravertebral line - on level of the XI heads of rib.
Inferior border of right pleura lies
1 cm beneath from lung border.
Note that a left lung and pleura inferior boundary path is situated 1- 2 cm beneath, than right.