1. lіver. gall bladder. pancreas
2. perіtoneum (visceral and parietal sheets).
3. External nose. nasal cavity. larynx
Lesson No 13
Theme 1. lіver. gall bladder. pancreas
The liver, the largest gland in the body, also performs important exocrine and metabolic functions:
· The secretion of bile.
· The protective role by detoxifying substances.
· The storehouse for various substances.
· Metabolising the products of digestion.
· The synthesis of proteins.
· The metabolism of carbohydrates and the regulation of blood glucose.
· The metabolism of fats and the regulation of blood lipids.
· The conjugation of substances.
· The transformation of substances.
· The production of carbohydrates from proteins.
· The haemopoietic function - especially during foetal life the liver is a centre for haemopoiesis and new-born.
· The production of thrombolitic agents.
· The synthesis of procoagulants.
Topography of the liver. Holotopy: Liver occupies
right hypochondriac region, proper epigastric region and small part of left
hypochondriac region. Skeletotopy: The upper edge of the liver projects in
right 10th intercostal space (middle axillar line). Than it lifts to level of
4th rib (middle clavicular line) and passes across the sternum a bit upper from
xiphoid process, terminates in left 5th intercostal space (between middle
clavicular line and parasternal lines). The lower edge of the
liver passes along the costal arch from right 10th intercostal space (middle
axillar line). Than it crosses cartilage of right 9th rib and runs in
epigastrium 1,5 cm
lower from xiphoid process to cartilage of left 8th rib and meets the upper
margin.
Inferior surface of the liver
We distinguish the convex diaphragmatic surface of the liver and lower visceral surface. Visceral surface adjoins to the organs, which form on surface of the liver suitable ‘tracks’: renal, adrenal, gastric, duodenal, oesophageal and colic impressions. Diaphragmatic surface carries cardiac impression.
Liver is almost entirely covered with peritoneum except posteriorly positioned ‘area nuda’. The superior surface is attached to the diaphragm and anterior abdominal wall by a fold of peritoneum, the falciform ligament, in the free margin of which is a rounded cord, the ligamentum teres (obliterated umbilical vein). The liver is connected to the lower surface of the diaphragm by the coronal ligament and the right and left triangular ligaments. The falciform ligament conventionally separates greater right lobe of liver and lesser left lobe of liver.
The porta hepatis, the entrance into the liver forms a cross-connection between the sagittal grooves which together are shaped like an H. Visceral surface carries furrows: right sagittal sulcus and left sagittal sulcus, which communicate by transversal sulcus (is called ‘porta hepatis’). Left sagittal sulcus anteriorly contain fissure of teres ligament, where umbilical vein in foetus passes. It obliterates in adult and forms teres liver ligament. Posterior portion of left sagittal sulcus is formed by fissura of venous ligament (obliterated venous duct of Arantii). Right sagittal sulcus anteriorly contains fossa of gall bladder, and behind - sulcus of inferior vena cava. Vena portae, proper hepatic artery and nerves enter through the porta hepatis into liver, common hepatic duct and lymphatic vessels leave the parenchyma in this place. Sagittal and transversal sulcuses limit the quadrate lobe, positioned ventrally and caudate lobe, disposed dorsally. Caudate lobe carries papillary and caudate processes.
The liver is held together by a tense connective tissue capsule Glisson 's capsule. At the porta it separates the lobules of liver. The lobules form the chief mass of the hepatic substance. Branches of portal vein, hepatic artery and biliary duct form a hepatic triad are situated in stratums between liver lobules.
Unlike all other organs a liver obtains arterial blood from proper hepatic artery and venous - from portal vein. Entering into liver porta, a portal vein and hepatic artery disintegrate into right and left lobar, segmental and lobular veins and arteries, which pass along interlobular bile duct. Capillaries from these vessels joining together form sinusoid capillaries that receive mixed blood and empty into a central vein, which occupies the centre of the lobule. Central vein drains into hepatic veins, which leave the liver to end in the inferior vena cava. This system is called as wonderful venous liver net.
Hepatic cells ‘hepatocytes’ excrete the bile, which get into bile canaliculi. Last pass to periphery emtpy into interlobular ductuli that form right hepatic duct and left hepatic duct (from right and left hepatic lobes). Common hepatic duct, which originated in porta, passes in hepatoduodenal ligament, meets the cystic duct and forms ductus choledochus. It flows together with pancreatic duct and forms common hepalopancreatic ampulla, which opens on major duodenal papilla. The ampulla may itself be closed by its own sphincter muscle, the sphincter ampullae (Oddi).
The liver, the largest gland in the
body, has both external and internal secretions, which are formed in the
hepatic cells. Its external secretion, the bile, is collected after
passing through the bile capillaries by the bile ducts, which join like the
twigs and branches of a tree to form two large ducts that unite to form the
hepatic duct. The bile is either carried to the gall-bladder by the cystic duct
or poured directly into the duodenum by the common bile duct where it aids in digestion.
The internal secretions are concerned with the metabolism of both nitrogenous
and carbohydrate materials absorbed from the intestine and carried to the liver
by the portal vein. The carbohydrates are stored in the hepatic cells in the
form of glycogen which is secreted in the form of sugar directly into the blood
stream. Some of the cells lining the blood capillaries of the liver are
concerned in the destruction of red blood corpuscles. It is situated in the
upper and right parts of the abdominal cavity, occupying almost the whole of
the right hypochondrium, the greater part of the epigastrium, and not
uncommonly extending into the left hypochondrium as far as the mammillary line.
In the male it weighs from 1.4 to 1.6 kilogm., in the female from 1.2 to 1.4
kilogm. It is relatively much larger in the fetus than in the adult,
constituting, in the former, about one-eighteenth, and in the latter about one
thirty-sixth of the entire body weight. Its greatest transverse measurement is
from 20 to
To obtain a correct idea of its shape it must be hardened in situ, and it will then be seen to present the appearance of a wedge, the base of which is directed to the right and the thin edge toward the left. Symington describes its shape as that “of a right-angled triangular prism with the right angle rounded off.”
Surfaces.—The liver possesses three surfaces, viz., superior, inferior and posterior. A sharp, well-defined margin divides the inferior from the superior in front; the other margins are rounded. The superior surface is attached to the diaphragm and anterior abdominal wall by a triangular or falciform fold of peritoneum, the falciform ligament, in the free margin of which is a rounded cord, the ligamentum teres (obliterated umbilical vein). The line of attachment of the falciform ligament divides the liver into two parts, termed the right and left lobes, the right being much the larger. The inferior and posterior surfaces are divided into four lobes by five fossae, which are arranged in the form of the letter H. The left limb of the H marks on these surfaces the division of the liver into right and left lobes; it is known as the left sagittal fossa, and consists of two parts, viz., the fossa for the umbilical vein in front and the fossa for the ductus venosus behind. The right limb of the H is formed in front by the fossa for the gall-bladder, and behind by the fossa for the inferior vena cava; these two fossae are separated from one another by a band of liver substance, termed the caudate process. The bar connecting the two limbs of the H is the porta (transverse fissure); in front of it is the quadrate lobe, behind it the caudate lobe.
The superior surface (facies superior) comprises a part of both lobes, and, as a whole, is convex, and fits under the vault of the diaphragm which in front separates it on the right from the sixth to the tenth ribs and their cartilages, and on the left from the seventh and eighth costal cartilages. Its middle part lies behind the xiphoid process, and, in the angle between the diverging rib cartilage of opposite sides, is in contact with the abdominal wall. Behind this the diaphragm separates the liver from the lower part of the lungs and pleurae, the heart and pericardium and the right costal arches from the seventh to the eleventh inclusive. It is completely covered by peritoneum except along the line of attachment of the falciform ligament.
The superior surface of the liver
The inferior surface (facies inferior; visceral surface)is uneven, concave, directed downward, backward, and to the left, and is in relation with the stomach and duodenum, the right colic flexure, and the right kidney and suprarenal gland. The surface is almost completely invested by peritoneum; the only parts devoid of this covering are where the gall-bladder is attached to the liver, and at the porta hepatis where the two layers of the lesser omentum are separated from each other by the bloodvessels and ducts of the liver. The inferior surface of the left lobe presents behind and to the left the gastric impression, moulded over the antero-superior surface of the stomach, and to the right of this a rounded eminence, the tuber omentale, which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of the lesser omentum. The under surface of the right lobe is divided into two unequal portions by the fossa for the gall-bladder; the portion to the left, the smaller of the two, is the quadrate lobe, and is in relation with the pyloric end of the stomach, the superior portion of the duodenum, and the transverse colon. The portion of the under surface of the right lobe to the right of the fossa for the gall-bladder presents two impressions, one situated behind the other, and separated by a ridge. The anterior of these two impressions, the colic impression, is shallow and is produced by the right colic flexure; the posterior, the renal impression, is deeper and is occupied by the upper part of the right kidney and lower part of the right suprarenal gland. Medial to the renal impression is a third and slightly marked impression, lying between it and the neck of the gall-bladder. This is caused by the descending portion of the duodenum, and is known as the duodenal impression. Just in front of the inferior vena cava is a narrow strip of liver tissue, the caudate process, which connects the right inferior angle of the caudate lobe to the under surface of the right lobe. It forms the upper boundary of the epiploic foramen of the peritoneum.
Posterior and inferior surfaces of the liver.
The
posterior surface (facies posterior) is rounded and broad behind
the right lobe, but narrow on the left. Over a large part of its extent it is
not covered by peritoneum; this uncovered portion is about
The anterior border (margo anterior) is thin and sharp, and marked opposite the attachment of the falciform ligament by a deep notch, the umbilical notch, and opposite the cartilage of the ninth rib by a second notch for the fundus of the gall-bladder. In adult males this border generally corresponds with the lower margin of the thorax in the right mammillary line; but in women and children it usually projects below the ribs.
The left extremity of the liver is thin and flattened from above downward.
Fossae.—The left sagittal fossa (fossa sagittalis sinistra; longitudinal fissure) is a deep groove, which extends from the notch on the anterior margin of the liver to the upper border of the posterior surface of the organ; it separates the right and left lobes. The porta joins it, at right angles, and divides it into two parts. The anterior part, or fossa for the umbilical vein, lodges the umbilical vein in the fetus, and its remains (the ligamentum teres) in the adult; it lies between the quadrate lobe and the left lobe of the liver, and is often partially bridged over by a prolongation of the hepatic substance, the pons hepatis. The posterior part, or fossa for the ductus venosus, lies between the left lobe and the caudate lobe; it lodges in the fetus, the ductus venosus, and in the adult a slender fibrous cord, the ligamentum venosum, the obliterated remains of that vessel.
The
porta or transverse fissure (porta hepatis) is a short but
deep fissure, about
The fossa for the gall-bladder (fossa vesicae felleae) is a shallow, oblong fossa, placed on the under surface of the right lobe, parallel with the left sagittal fossa. It extends from the anterior free margin of the liver, which is notched by it, to the right extremity of the porta.
The fossa for the inferior vena cava (fossa venae cavae) is a short deep depression, occasionally a complete canal in consequence of the substance of the liver surrounding the vena cava. It extends obliquely upward on the posterior surface between the caudate lobe and the bare area of the liver, and is separated from the porta by the caudate process. On slitting open the inferior vena cava the orifices of the hepatic veins will be seen opening into this vessel at its upper part, after perforating the floor of this fossa.
Lobes.—The right lobe (lobus hepatis dexter) is much larger than the left; the proportion between them being as six to one. It occupies the right hypochondrium, and is separated from the left lobe on its upper surface by the falciform ligament; on its under and posterior surfaces by the left sagittal fossa; and in front by the umbilical notch. It is of a somewhat quadrilateral form, its under and posterior surfaces being marked by three fossae: the porta and the fossae for the gall-bladder and inferior vena cava, which separate its left part into two smaller lobes; the quadrate and caudate lobes. The impressions on the right lobe have already been described.
The quadrate lobe (lobus quadratus) is situated on the under surface of the right lobe, bounded in front by the anterior margin of the liver; behind by the porta; on the right, by the fossa for the gall-bladder; and on the left, by the fossa for the umbilical vein. It is oblong in shape, its antero-posterior diameter being greater than its transverse.
The caudate lobe (lobus caudatus; Spigelian lobe) is situated upon the posterior surface of the right lobe of the liver, opposite the tenth and eleventh thoracic vertebrae. It is bounded, below, by the porta; on the right, by the fossa for the inferior vena cava; and, on the left, by the fossa for the ductus venosus. It looks backward, being nearly vertical in position; it is longer from above downward than from side to side, and is somewhat concave in the transverse direction. The caudate process is a small elevation of the hepatic substance extending obliquely lateralward, from the lower extremity of the caudate lobe to the under surface of the right lobe. It is situated behind the porta, and separates the fossa for the gall-bladder from the commencement of the fossa for the inferior vena cava.
The left lobe (lobus hepatis sinister) is smaller and more flattened than the right. It is situated in the epigastric and left hypochondriac regions. Its upper surface is slightly convex and is moulded on to the diaphragm; its under surface presents the gastric impression and omental tuberosity, already referred to page 1189.
Ligaments.—The liver is connected to the under surface of the diaphragm and to the anterior wall of the abdomen by five ligaments; four of these—the falciform, the coronary, and the two lateral—are peritoneal folds; the fifth, the round ligament, is a fibrous cord, the obliterated umbilical vein. The liver is also attached to the lesser curvature of the stomach by the hepatogastric and to the duodenum by the hepatoduodenal ligament.
The falciform ligament (ligamentum falciforme hepatis) is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed downward and backward, its apex upward and backward. It is situated in an antero-posterior plane, but lies obliquely so that one surface faces forward and is in contact with the peritoneum behind the right Rectus and the diaphragm, while the other is directed backward and is in contact with the left lobe of the liver. It is attached by its left margin to the under surface of the diaphragm, and the posterior surface of the sheath of the right Rectus as low down as the umbilicus; by its right margin it extends from the notch on the anterior margin of the liver, as far back as the posterior surface. It is composed of two layers of peritoneum closely united together. Its base or free edge contains between its layers the round ligament and the parumbilical veins.
The coronary ligament (ligamentum coronarium hepatis) consists of an upper and a lower layer. The upper layer is formed by the reflection of the peritoneum from the upper margin of the bare area of the liver to the under surface of the diaphragm, and is continuous with the right layer of the falciform ligament. The lower layer is reflected from the lower margin of the bare area on to the right kidney and suprarenal gland, and is termed the hepatorenal ligament.
The triangular ligaments (lateral ligaments) are two in number, right and left. The right triangular ligament (ligamentum triangulare dextrum) is situated at the right extremity of the bare area, and is a small fold which passes to the diaphragm, being formed by the apposition of the upper and lower layers of the coronary ligament. The left triangular ligament (ligamentum triangulare sinistrum) is a fold of some considerable size, which connects the posterior part of the upper surface of the left lobe to the diaphragm; its anterior layer is continuous with the left layer of the falciform ligament.
The round ligament (ligamentum teres hepatis) is a fibrous cord resulting from the obliteration of the umbilical vein. It ascends from the umbilicus, in the free margin of the falciform ligament, to the umbilical notch of the liver, from which it may be traced in its proper fossa on the inferior surface of the liver to the porta, where it becomes continuous with the ligamentum venosum.
Fixation of the Liver.—Several factors contribute to maintain the liver in place. The attachments of the liver to the diaphragm by the coronary and triangular ligaments and the intervening connective tissue of the uncovered area, together with the intimate connection of the inferior vena cava by the connective tissue and hepatic veins would hold up the posterior part of the liver. Some support is derived from the pressure of the abdominal viscera which completely fill the abdomen whose muscular walls are always in a state of tonic contraction. The superior surface of the liver is perfectly fitted to the under surface of the diaphragm so that atmospheric pressure alone would be enough to hold it against the diaphragm. The latter in turn is held up by the negative pressure in the thorax. The lax falciform ligament certainly gives no support though it probably limits lateral displacement.
Liver
with the septum transversum. Human embryo
Vessels and Nerves.—The vessels connected with the liver are: the hepatic artery, the portal vein, and the hepatic veins.
The hepatic artery and portal vein, accompanied by numerous nerves, ascend to the porta, between the layers of the lesser omentum. The bile duct and the lymphatic vessels descend from the porta between the layers of the same omentum. The relative positions of the three structures are as follows: the bile duct lies to the right, the hepatic artery to the left, and the portal vein behind and between the other two. They are enveloped in a loose areolar tissue, the fibrous capsule of Glisson, which accompanies the vessels in their course through the portal canals in the interior of the organ.
The hepatic veins convey the blood from the liver, and are described on page 680. They have very little cellular investment, and what there is binds their parietes closely to the walls of the canals through which they run; so that, on section of the organ, they remain widely open and are solitary, and may be easily distinguished from the branches of the portal vein, which are more or less collapsed, and always accompanied by an artery and duct.
The lymphatic vessels of the liver are described on page 711.
The nerves of the liver, derived from the left vagus and sympathetic, enter at the porta and accompany the vessels and ducts to the interlobular spaces. Here, according to Korolkow, the medullated fibers are distributed almost exclusively to the coats of the bloodvessels; while the non-medullated enter the lobules and ramify between the cells and even within them.
Structure of the Liver.—The substance of the liver is composed of lobules, held together by an extremely fine areolar tissue, in which ramify the portal vein, hepatic ducts, hepatic artery, hepatic veins, lymphatics, and nerves; the whole being invested by a serous and a fibrous coat.
The serous coat (tunica serosa) is derived from the peritoneum, and invests the greater part of the surface of the organ. It is intimately adherent to the fibrous coat.
The fibrous coat (capsula fibrosa [Glissoni]; areolar coat) lies beneath the serous investment, and covers the entire surface of the organ. It is difficult of demonstration, excepting where the serous coat is deficient. At the porta it is continuous with the fibrous capsule of Glisson, and on the surface of the organ with the areolar tissue separating the lobules.
The
lobules (lobuli hepatis) form the chief mass of the hepatic
substance; they may be seen either on the surface of the organ, or by making a
section through the gland, as small granular bodies, about the size of a
millet-seed, measuring from 1 to
A single lobule of the liver
If one of the sublobular veins be laid open, the bases of the lobules may be seen through the thin wall of the vein on which they rest, arranged in a form resembling a tesselated pavement, the center of each polygonal space presenting a minute aperture, the mouth of an intralobular vein .
Microscopic Appearance—Each lobule consists of a mass of cells, hepatic cells, arranged in irregular radiating columns between which are the blood channels (sinusoids). These convey the blood from the circumference to the center of the lobule, and end in the intralobular vein, which runs through its center, to open at its base into one of the sublobular veins. Between the cells are also the minute bile capillaries. Therefore, in the lobule there are all the essentials of a secreting gland; that is to say: (1) cells, by which the secretion is formed; (2) bloodvessels, in close relation with the cells, containing the blood from which the secretion is derived; (3) ducts, by which the secretion, when formed, is carried away.
The hepatic artery, entering the liver at the porta with the portal vein and hepatic duct, ramifies with these vessels through the portal canals. It gives off vaginal branches, which ramify in the fibrous capsule of Glisson, and appear to be destined chiefly for the nutrition of the coats of the vessels and ducts. It also gives off capsular branches, which reach the surface of the organ, ending in its fibrous coat in stellate plexuses. Finally, it gives off interlobular branches, which form a plexus outside each lobule, to supply the walls of the interlobular veins and the accompanying bile ducts. From this plexus lobular branches enter the lobule and end in the net-work of sinusoids between the cells.
The portal vein also enters at the porta, and runs through the portal canals, enclosed in Glisson’s capsule, dividing in its course into branches, which finally break up into a plexus, the interlobular plexus, in the interlobular spaces. These branches receive the vaginal and capsular veins, corresponding to the vaginal and capsular branches of the hepatic artery. Thus it will be seen that all the blood carried to the liver by the portal vein and hepatic artery finds its way into the interlobular plexus. From this plexus the blood is carried into the lobule by fine branches which converge from the circumference to the center of the lobule, and are connected by transverse branches. The walls of these small vessels are incomplete so that the blood is brought into direct relationship with the liver cells. The lining endothelium consists of irregularly branched, disconnected cells (stellate cells of Kupffer). Moreover, according to Herring and Simpson, minute channels penetrate the liver cells themselves, conveying the constituents of the blood into their substance. It will be seen that the blood capillaries of the liver lobule differ structurally from capillaries elsewhere. Developmentally they are formed by the growth of the columns of liver cells into large blood spaces or sinuses, and hence they have received the name of “sinusoids.” Arrived at the center of the lobule, the sinusoids empty themselves into one vein, of considerable size, which runs down the center of the lobule from apex to base, and is called the intralobular vein. At the base of the lobule this vein opens directly into the sublobular vein, with which the lobule is connected. The sublobular veins unite to form larger and larger trunks, and end at last in the hepatic veins, these converge to form three large trunks which open into the inferior vena cava while that vessel is situated in its fossa on the posterior surface of the liver.
3. The bile ducts commence by little passages in the liver cells which communicate with canaliculi termed intercellular biliary passages (bile capillaries). These passages are merely little channels or spaces left between the contiguous surfaces of two cells, or in the angle where three or more liver cells meet, and they are always separated from the blood capillaries by at least half the width of a liver cell. The channels thus formed radiate to the circumference of the lobule, and open into the interlobular bile ducts which run in Glisson’s capsule, accompanying the portal vein and hepatic artery. These join with other ducts to form two main trunks, which leave the liver at the transverse fissure, and by their union form the hepatic duct.
Structure of the Ducts.—The walls of the biliary ducts consist of a connective-tissue coat, in which are muscle cells, arranged both circularly and longitudinally, and an epithelial layer, consisting of short columnar cells resting on a distinct basement membrane.
Excretory Apparatus of the Liver.—The excretory apparatus of the liver consists of (1) the hepatic duct, formed by the junction of the two main ducts, which pass out of the liver at the porta; (2) the gall-bladder, which serves as a reservoir for the bile; (3) the cystic duct, or the duct of the gall-bladder; and (4) the common bile duct, formed by the junction of the hepatic and cystic ducts.
The
Hepatic Duct (ductus hepaticus).—Two main
trunks of nearly equal size issue from the liver at the porta, one from the
right, the other from the left lobe; these unite to form the hepatic duct,
which passes downward and to the right for about
The
Gall-bladder (vesica fellea) is a conical or pear-shaped
musculomembranous sac, lodged in a fossa on the under surface of the right lobe
of the liver, and extending from near the right extremity of the porta to the
anterior border of the organ. It is from 7 to
The gall-bladder and bile ducts laid open.
Relations.—The body is in relation, by its upper surface, with the liver; by its under surface, with the commencement of the transverse colon; and farther back usually with the upper end of the descending portion of the duodenum, but sometimes with the superior portion of the duodenum or pyloric end of the stomach. The fundus is completely invested by peritoneum; it is in relation, in front, with the abdominal parietes, immediately below the ninth costal cartilage; behind with the transverse colon. The neck is narrow, and curves upon itself like the letter S; at its point of connection with the cystic duct it presents a well-marked constriction.
Structure—The gall-bladder consists of three coats: serous, fibromuscular, and mucous.
The external or serous coat (tunica serosa vesicae felleae) is derived from the peritoneum; it completely invests the fundus, but covers the body and neck only on their under surfaces.
The fibromuscular coat (tunica muscularis vesicae felleae), a thin but strong layer forming the frame-work of the sac, consists of dense fibrous tissue, which interlaces in all directions, and is mixed with plain muscular fibers, disposed chiefly in a longitudinal direction, a few running transversely.
The internal or mucous coat (tunica mucosa vesicae felleae) is loosely connected with the fibrous layer. It is generally of a yellowish-brown color, and is elevated into minute rugae. Opposite the neck of the gall-bladder the mucous membrane projects inward in the form of oblique ridges or folds, forming a sort of spiral valve.
The mucous membrane is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver, and through the common bile duct with the mucous membrane of the duodenum. It is covered with columnar epithelium, and secretes mucin; in some animals it secretes a nucleoprotein instead of mucin.
The
Cystic Duct (ductus cysticus).—The cystic duct about
The
Common Bile Duct (ductus choledochus).—The common bile duct is
formed by the junction of the cystic and hepatic ducts; it is about
It
descends along the right border of the lesser omentum behind the superior
portion of the duodenum, in front of the portal vein, and to the right of the
hepatic artery; it then runs in a groove near the right border of the posterior
surface of the head of the pancreas; here it is situated in front of the
inferior vena cava, and is occasionally completely imbedded in the pancreatic
substance. At its termination it lies for a short distance along the right side
of the terminal part of the pancreatic duct and passes with it obliquely
between the mucous and muscular coats. The two ducts unite and open by a common
orifice upon the summit of the duodenal papilla, situated at the medial side of
the descending portion of the duodenum, a little below its middle and about 7
to
Structure.—The coats of the large biliary ducts are an external or fibrous, and an internal or mucous. The fibrous coat is composed of strong fibroareolar tissue, with a certain amount of muscular tissue, arranged, for the most part, in a circular manner around the duct. The mucous coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with that of the duodenum; and, like the mucous membrane of these structures, its epithelium is of the columnar variety. It is provided with numerous mucous glands, which are lobulated and open by minute orifices scattered irregularly in the larger ducts.
The Gallbladder is a pear-shaped, thin-walled bag, which collects up to 30-50 ml bile. We distinguish fundus, body and neck of gallbladder, which continues into cystic duct. The gallbladder lies in a fossa in the liver to which it is attached by connective tissue and covered by peritoneum from below (mesoperitoneal position). The lumen of the neck of the gallbladder and of its connections with the cystic duct is incompletely subdivided by spiral fold of mucosa, known as the spiral fold (Heisler's valve).
The pancreas is the most important intestinal gland. The pancreas is shaped like a horizontal wedge with its thin end on the left. The head is the thickest part, fills into the duodenal loop to the right of the spine. The horizontal body continues into tail. The pancreatic duct runs right through the length of the gland. It receives short, vertical tributaries from the lobules and has owns sphincter muscle of pancreatic duct. The pancreatic duct ends together with the common bile duct on the major duodenal papilla. If present, the accessory pancreatic duct ends above the bile duct on the minor duodenal papilla.
Topography of the pancreas. Pancreas lies in upper abdominal region behind the peritoneum (retroperitoneal position) at the level of the from 1st to 3d lumbar vertebrae. Along the upper margin of the pancreas runs the splenic artery. The right kidney and adrenal gland adjoin to body of pancreas. Anterior surface of gland touches the stomach, posterior surface – inferior vena cava and aorta. Tail adjoins to splenic hilus.
Endocrine part of pancreas is represented by islets of Langerhans. They produce insulin and glucagon that regulate metabolism of carbohydrates, regulative a sugar contents in organism. Attached to insufficient production of these hormonal disease sugar diabetes arises.
Theme 2. perіtoneum (visceral and parietal sheets)
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.
Vertical disposition of the peritoneum. Main cavity, red; omental bursa, blue.
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.
The PERITONEUM is serous membrane that covers the walls of abdominal cavity and viscera in abdomen and pelvis. It may be subdivided into parietal peritoneum and visceral peritoneum. 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.
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.
The
abdomen is the largest cavity in the body. It is of an oval shape, the
extremities of the oval being directed upward and downward. The upper extremity
is formed by the diaphragm which extends as a dome over the abdomen, so that
the cavity extends high into the bony thorax, reaching on the right side, in
the mammary line, to the upper border of the fifth rib; on the left side it
falls below this level by about
The abdomen proper differs from the other great cavities of the body in being bounded for the most part by muscles and fasciae, so that it can vary in capacity and shape according to the condition of the viscera which it contains; but, in addition to this, the abdomen varies in form and extent with age and sex. In the adult male, with moderate distension of the viscera, it is oval in shape, but at the same time flattened from before backward. In the adult female, with a fully developed pelvis, it is ovoid with the narrower pole upward, and in young children it is also ovoid but with the narrower pole downward.
Boundaries.—It is bounded in front and at the sides by the abdominal muscles and the Iliacus muscles; behind by the vertebral column and the Psoas and Quadratus lumborum muscles; above by the diaphragm; below by the plane of the superior aperture of the lesser pelvis. The muscles forming the boundaries of the cavity are lined upon their inner surfaces by a layer of fascia.
The abdomen contains the greater part of the digestive tube; some of the accessory organs to digestion, viz., the liver and pancreas; the spleen, the kidneys, and the suprarenal glands. Most of these structures, as well as the wall of the cavity in which they are contained, are more or less covered by an extensive and complicated serous membrane, the peritoneum.
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.
The pelvis is that portion of the abdominal cavity which lies below and behind a plane passing through the promontory of the sacrum, lineae 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.
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.
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, lineae 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).
Vertical disposition of the peritoneum. Main cavity, red; omental bursa, blue
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 of 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 run.
Theme 3. External nose. nasal cavity. larynx.
The respiratory apparatus consists of the nose, nasal cavity, larynx, trachea, bronchi, lungs, and pleurae.
The head and neck of a human embryo thirty-two days old, seen from the ventral surface. The floor of the mouth and pharynx have been removed
Lungs of a human embryo more advanced in development.
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 vibrissae, 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 maxillae.
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 maxillae.
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.
Cartilages of the nose. Side view.
Cartilages of the nose, seen from below.
Bones and cartilages of septum of nose. Right side.
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 alae 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.
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 choanae with the nasal part of the pharynx. The nares are
somewhat pear-shaped apertures, each measuring about
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 conchae, 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.
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 choanae. 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 conchae. 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 conchae appear larger and more prominent than in the skeleton; also the various apertures communicating with the meatuses are considerably narrowed.
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.
Nerves of septum of nose. Right side
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,
Coronal section of nasal cavities.
The Ethmoidal Air Cells (cellulae 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 laminae. 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, cellulae ethmoidales, anterior and posterior, infundibulum ethmoidale, and the primitive sinus frontalis are brought into view.
Specimen from a child one year, four months, and seven days old. Lateral view of frontal, ethmoidal, and maxillary sinus areas.
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.
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.
Paired cartilages:
• 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 vertebrae, 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:
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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:
Thyroid.
Cricoid.
Two Arytenoid.
Two Corniculate.
Two Cuneiform. Epiglottis
The Thyroid Cartilage (cartilago thyreoidea) is the largest cartilage of the larynx. It consists of two laminae 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 laminae are separated by a V-shaped notch, the superior thyroid notch. The laminae 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 laminae, are attached the stem of the epiglottis, the ventricular and vocal ligaments, the Thyreoarytaenoidei, 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 laminae 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 laminae 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 cricoideae; posterior portion)
is deep and broad, and measures from above downward about 2 or
The arch (arcus cartilaginis cricoideae; 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 Cricoarytaenoidei 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 arytaenoideae) 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 Arytaenoidei 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 foveae, 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 Cricoarytaenoideus posterior behind, and to the Cricoarytaenoideus 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 corniculatae; 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 laminae 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 valleculae. 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.
Ligaments of the larynx. Posterior view.
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.
Sagittal section of the larynx and upper part of the trachea
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.
Coronal section of larynx and upper part of trachea.
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 Thyreoarytaenoideus. 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 entrance to the larynx, viewed from behind.
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
Laryngoscopic view of interior of larynx.)
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:
Cricothyreoideus.
Cricoarytaenoideus lateralis.
Cricoarytaenoideus posterior.
Arytaenoideus.
Thyroarytaenoideus.
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 Cricoarytaenoideus posterior (posterior cricoarytenoid) 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 Cricoarytaenoideus lateralis (lateral cricoarytenoid) 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.
Side view of the larynx, showing muscular attachments.
Muscles of larynx. Side view. Right lamina of thyroid cartilage removed.
The Arytaenoideus 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 Arytaenoideus 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 Arytaenoideus transversus crosses transversely between the two cartilages.
The Thyreoarytaenoideus (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.
Muscles of larynx. Posterior view.
Muscles of larynx. Side view. Right lamina of thyroid cartilage removed.
A considerable number of the fibers of the Thyreoarytaenoideus 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.
Muscles of the larynx, seen from above.
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.
Prepared by
Reminetskyy B.Y.
