LIVER features, location, structures,blood supply, and it's function
Features
The liver is a large, solid, gland situated in the rightupper quadrant of the abdominal cavity. In the living
subject, the liver is reddish brown in colour, soft in
consistency, andvery friable. It weighs about 1600 g in
males and about 1300 g in females.
Location
The liver occupies the whole of the right hypo-chondrium, the greater part of the epigastrium, and
extends into the left hypochondrium reaching up to the
left lateral line. From the above it will be obvious that
most of the liver is covered by ribs and costal cartilages,
except in the upper part of the epigastrium where it is
in contact with the anterior abdominal wall .
The liver is the largest gland in the body. It secretes
bile and performs various other metabolic functions.
The liver is also called the 'hepar' from which we
have the adjective 'hepatic' applied to many structures
connected with the organ.
External features
The liver is wedge-shaped. It resembles a four-sidedpyramid laid on one side .
Five surfaces
It has five surfaces. These are:1 Anterior,
2 Posterior,
3 Superior
4 Inferior
5 Right
Out of these the inferior surface is well defined
because it is demarcated, anteriorly,by a sharp inferior
border. The other surfaces are more or less continuous
with each other and are imperfectly separated from one
another by ill-defined, rounded borders.
One Prominent border
Tine inferior border is sharp anteriorly where it separatesthe anterior surface from the inferior surface. It is
somewhat rounded laterally where it separates the right
surface from the inferior surface. The sharp anterior
part is marked by:
a. An interlobar nofck or the notch for the ligamentum
teres.
b. A cystic notch for the fundus of the gallbladder.
In the epigastrium, the inferior border extends from the left 8th costal cartilage to the right 9th costal cartilage.
Two Lobes
The liver is divided into right and left lobes by attachment of the falciform lignment anteriorly and superiorly; by the fissure for the ligamentum teres inferiorly; and by the fissure for the ligamentum rsenosum
posteriorly.
The right lobe is much larger than the left lobe, and forms five sixth of the liver. It contributes to all the five surfaces of the liver, and Presents the caudate and
quadrate lobes.
The caudate lobe is situated on the posterior surface. It is bounded on the right by the groove for the inferior vanacava, on the left by the fissure for the ligamentum
Venosum, and inferiorly by the portahepatis. Above it is continuous with the superior surface. Below and to the
right, just behind the porta hepatis, it is connected to the right lobe of the liver by the caudate process. Below and to the left it presents a small rounded elevation called the papillary process.
The quadrate lobe is situated on the inferior surface ,and is rectangular in shape. It is bounded by anteriorly by inferior border , posteriorly by porta hepatis , on the right by the fossa for the gall bladder , and on the left by the fissure for the ligamentum teres.
The left lobe of the Liver is much smaller than the right lobe and forms one - sixth of the Liver. It is flattened from above downwards . Near the fissure for the ligamentum venosum , it's inferior surface presents a rounded elevation, called the omentale tuberosity or tuber omentale.
Relations
Peritoneal relations
Most of the liver is covered by peritoneum. The areas not covered by peritoneum are as follows:
1. A triangular bare area , on the posterior surface of right lobe .
2. The groove for the inferior venacava on the posterior surface of the right lobe of the liver, between the caudate lobe and bare area.
3. The fossa for the gall bladder which lies on the inferior surface of the right lobe to the right of the quadrate lobe.
4. The lesser omentum.
Visceral Relations
Anterior surface
The anterior surface is triangular and slightly convex. It is related to the xiphoid process and to the anterior abdominal wall in the median plane; and to diaphragm
on each side. The diaphragm separates this surface from the pleura above the level of a line drawn from the xiphisternal joint to the 10th rib in the midaxillary line;
and from the lung above the level of a line from the same joint to the 8th rib. The falciform ligament is attached to this surface a little to the right of the median plane.
Posterior surface
The posterior surface is triangular. Its middle part shows a deep concavity for the vertebral column. Other relations are as follows.
1 The bare area is related to the diaphragm; and to the right suprarenal gland near the lower end of the groove for the inferior vena cava.
2 The groove for the inferior vanacava lodges the upper part of the vessel, and its floor is pierced by the hepatic veins.
3 The caudate lobeliesin the superior recess of the lesser sac. It is related to the crura of the diaphragm above the aortic opening, to the right inferior phrenic artery, and to the coeliac trunk.
4 The fissure for the ligamentum oenosum is very deep and extends to the front of the caudate lobe. It contains two layers of the lesser omentum. The ligamentum venosum lies on its floor. The ligamentum venosum is a remnant of the ductus venosus of foetal life; it is connected below to the
left branch of the portal vein, and above to the left hepatic veinnear its entry into the inferior vena cava.
5 The posterior surfnce of the left lobe is marked by the oesophageal impression.
Superior surface
The superior surface is quadrilateral and shows a concavity in the middle. This is the cardiac impression.
On each side of the impression the surface is convex to fit the dome of the diaphragm. The diaphragm separates this surface from the pericardium and the heart in the middle; and from pleura and lung on each
side.
Inferior surface
The inferior surface is quadrilateral and is directed, downwards backwards and to the left. It is marked by impressions for neighbouring viscera as follows.
1 On the inferior surface of the left lobe there is a large concave gastric impression. The left lobe also bears a raised area that comes in contact with the lesser omentum: it is called the omentale tuber.
2 The fissure for the ligamentum teres passes from the inferior border to the left end of the porta hepatis.The ligamentum teres represents the obliterated left
umbilical vein.
3 The quadrate lobe is related to the lesser omentum, the pylorus, and the first part of the duodenum.When the stomach is empty the quadrate lobe is related to the first part of the duodenum and to a part of the transverse colon.
4 The fossa for the gallbladder lies to the right of the quadratelobe.
5 To the right of this fossa the inferior surface of the right lobe bears the colic impression for the hepatic flexure of the colon, the renal impression for the right
kidney, and the duodenal impression for the second part of the duodenum.
Right surface
The right surface is quadrilateral and convex. It is relatedto the diaphragm opposite the 7th to 11th ribs in the midaxillary line. It is separated by the diaphragm from the pleura up to the 10th rib, and from the lung up to the 8th rib. Thus, the upper one-third of the
surface is related to the diaphragm, the pleura and the lung; the middle one-third, to the diaphragm and the costodiaphragmatic recess of the pleura; and the lower one-third to the diaphragm alone.
Blood supply
The liver receives 20% of its blood supply through the hepatic artery, and 80% through the portal vein. Before
entering the liver, both the hepatic artery and the portal vein divide into right and leftbranches. Within the liver,
they redivide to form segmental vessels which further divide to form interlobular vessels which run in the portal canals. Further ramifications of the interlobular
branches open into the hepatic sinusoids. Thus the hepatic arterial blood mixes with the portal venous blood in the sinusoids. There are no anastomoses between adjoining hepatic arterial territories and hence each branch is an end artery.
Venous drainage
Hepatic sinusoids drain into interlobular veins, which join to form sublobular veins. These in turn unite to form the hepatic veins which drain directly into the
inferior vena cava. These veins provide great suPPort to the liver, besides the intra-abdominal pressure.
The hepatic veins are arranged in two groups/ uPPer and lower. The upper group consists of three large veins
right,left and middle, which emerge through the uPper part of the groove for the inferior vena cava, and open
directly into the vena cava. These veins keep the liver suspended. The lower group consists of a variable number of small veins from the right lobe and the
caudate lobe which emerge through the lower part of the caval groove and open into the vena cava' Microscopically the tributaries of hepatic veins, i.e.
central veins are seen as separate channels from those of the portal radicles.
Lymphatic drainage
The superficial lymphatics of the liver run on the surface of the organ, and terminate in caval, coeliac lymph nodes. Some ligament maY directlY join the thoracic duct. The deep lymphatics end partly in the nodes around the end of the inferior vena cava, and partly in the hepatic nodes.
Nerve Supply
The liver receives its nerve supply from the hepatic plexus which contains both sympathetic and parasympathetic or vagal fibres. Nerves also reach the liver through its various peritoneal ligaments.
Hepatic segments
On the basis of the intrahepatic distribution of the hepatic artery, the portal vein and the biliary ducts, the liver can be divided into the right and left functional Lobes. These do not correspond to the anatomical lobes
of the liver. The physiological lobes are separated by a plane passing on the anterosuperior surface along a line
joining the cystic notch to the groove for the inferior vena cava. On the inferior surface the plane passes through the fossa for the gallbladder; and on the posterior surface it passes through the middle of the
caudate lobe.
The right lobe is subdivided into anterior and posterior segments, and the left lobe into medial and lateral segments. Thus there are four segments in the liver.
a. Right anterior (V and VII|,
b. Right posterior (VI and VII),
c. Left lateral (II and III) and
d. Left medial (I and IV).
The hepatic segments are of surgical importance. The hepatic veins tend to be intersegmental in their course.
FUNCTIONS
Liver is an indispensable gland of the body.
1 Metabolism of carbohydrates, fats and proteins;
2 Synthesis of bile and prothrombin;
3 Excretion of drugs, toxins, poisons, cholesterol, bile pigments and heavy metals;
4 Protectiae by conjugation, destruction, phagocytosis, antibody formation and excretion; and
5 Storage of glycogen, iron, fat, vitamin A and D.
Vijay Kumar Singh
BAMS (student)
BAMS (student)
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