1. l³ver. gall bladder. pancreas
2. per³toneum
(visceral and parietal sheets).
3. External nose. nasal cavity. larynx
Lesson No 13
Theme 1. l³ver. 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. per³toneum
(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:
|
|
In males. |
In females. |
|
Length |
|
|
|
Transverse diameter |
|
|
|
Antero-posterior diameter |
|
|
|
Circumference |
|
|
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.