Liver - Anatomy and Histology
By Shaazia Faiz
Liver, lying on top right of abdomen, just under the diaphragm is the controller of body in the sense that it has to check-and-balance all the extra, un-needed and hazardous substances that one ingests or produces in the body. Dealing with the toxic and non-toxic (but hazardous if in excess) chemicals, liver serves as a guard for the body, and in a way as an internal line of defense. Thus, diseases producing aberrations in structure or function of liver cause significant alterations from the physiologic state of body.
The liver performs over 500 jobs, and produces over 1,000 essential enzymes.
Because of the accuracy required for its functions, liver is designed very intricately, which needs explanation.
ANATOMY:
Liver is anatomically divided into 4 lobes(1), and is an encapsulated structure. It has dual blood supply, portal vein supplying 70% and hepatic artery with 30% of its required oxygen.
The liver is covered by visceral peritoneum completely, except at the region just under diaphragm, called the ‘bare area’. Falciform, and right and left triangular ligaments are formed by folding of visceral peritoneum. From behind, the lobes are divided up by the ligamentum venosum and ligamentum teres.
The porta hepatis or transverse fissure of the liver is a short but deep fissure, about 5 cm long, extending transversely. It is the central hilum through which portal vein, hepatic artery proper and common bile duct enter the liver.
HISTOLOGY:
The histology of liver is distinct from that of other organs in that every 3-4 cells (lobule) of it have their own vessels and their own drainage systems. No other organ in the body has such a deeply penetrating blood supply, with a separate vessel for each 3-4 cells.
The hepatocytes are arranged around the central vein, radiating away from it.
A collection of 3-4 hepatocytes along with their vasculature is called a lobule, although it varies with the model one chooses to study. The space between 3-4 lobules contains portal triad / tract.