Structure of Liver

April 29, 2019

It is the largest gland of our body.
It weighs between 1 to 2.3 kg which is situated in the upper right part of the abdominal cavity just below the diaphragm.
It’s upper and anterior surfaces are smooth and lie in close association to the posterior surface of diaphragm.
Similarly, its posterior surface is irregular in outline.
It is enclosed in a thin capsule and incompletely covered by a thin fold of peritoneum called falciparum ligament.
It attaches the liver to the diaphragm and keeps it in position.
The liver is made up of separate left and right lobes joined together by falciparum ligament.
The left lobe is smaller forming about 1/6 th of the liver.
The right lobe which is much larger is further incompletely divided by shallow fissures into three lobes.
They are: the largest right lobe proper, a small 4-sided caudate lobe and a small oblong quadrate lobe.
A pear-shaped sac-like gall bladder is attached to the posterior surface of the liver in between the right central and quadrate lobes.
It is a thin walled sac of dark green color that serves to store the secretions of liver.
A large cystic duct arises from the gall bladder which receives several hepatic ducts from different lobes of the liver carrying bile.
Thus, a large common bile duct is formed which opens in the proximal part of the duodenum.
The opening is guarded by a sphincter.

Histology

Histologically, each lobe of liver consists of a number of hepatic lobules separated from one another by a thin layer of connective tissue called septa or Glisson’s capsule.
In the liver of man and rabbit, septa demarcating the lobules are incomplete and not clearly marked off.
The lobules are just visible to naked eyes and are hexagonal in outline.
In the centre of each lobule lies a branch of hepatic vein, the intra-lobular vein or central vein.
The cells forming lobules are cuboidal or polyhedral in shape and are called hepatic cells.
These are arranged in radial rows of 1 or 2 cell thick rods or trabeculae which extend from the central vein to the periphery of the lobule.

Hepatic cell possess fine granular cytoplasm, large round central nuclei and deposits of glycogen and lipids.
Between hepatic cords is a labyrinth of narrow, irregular spaces called lacunae, through which run blood capillaries called hepatic sinusoids.
The walls of the sinusoids are dis-continuous and are made up of endothelial cells.
Some of these cells become highly phagocytic and are called cells of Kupffer which ingest dead and erythrocytes and destroy harmful bacteria.
At the corners between adjacent lobules are strands of inter-lobular connective tissue called portal areas or portal canals.
Each portal canals support a branch of hepatic artery, hepatic portal vein and bile duct which are often termed inter-lobular.

In addition to these, the portal canals also contain nerves and lymphatic vessels.
Sinusoids contain blood from inter-lobular branches of hepatic portal vein and hepatic artery and empty into the intra-lobular central veins which unite to form the hepatic vein.
Surrounding the liver cells is an intricate meshwork of fine inter-cellular channels or tubules, the bile capillaries.
Liver cells secrete bile directly into bile capillaries.
These join to form bile ductules which in turn open into hepatic ducts which ultimately form the common bile duct.