Accessory Organs of GIT

Emmanuel E.Siddig

Liver

• The liver is located primarily in the right hypochondriac and epigastric regions of the abdomen, just beneath the diaphragm. It is the largest gland in the body. On the surface, the liver is divided into two major lobes and two smaller lobes. The functional units of the liver are lobules with sinusoids that carry blood from the periphery to the central vein of the lobule.

• Liver is divided histologically into lobules. The center of the lobule is the central vein. At the periphery of the lobule are portal triads. Functionally, the liver can be divided into three zones, based upon oxygen supply. Zone 1 encircles the portal tracts where the oxygenated blood from hepatic arteries enters. Zone 3 is located around central veins, where oxygenation is poor. Zone 2 is located in between.

Gallbladder

• The gallbladder is a pear-shaped sac that is attached to the visceral surface of the liver by the cystic duct. The principal function of the gallbladder is to serve as a storage reservoir for bile. Bile is a yellowish-green fluid produced by liver cells. The main components of bile are water, bile salts, bile pigments, and cholesterol.

• In the gall bladder the epithelium is often folded and "caved". The gall bladder functions in the storage and concentration of bile. Microvilli on the apical surface of the epithelial cells facilitate the resorption of water from the bile.

Pancreas

• Has no distinct capsule, but is covered by a thin layer of loose connective tissue.

• Has both an exocrine( tubuloacinar glands) and endocrine gland.