Digestive System VI ppt.

Department of Anatomy &Histology Dr.Raja Ali
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Digestive System : Accessory Organs: Liver: (fig.1&2)
? The liver is the largest mass of glandular tissue in the body and the largest internal organ.
? It is unique because it receives its major blood supply from the hepatic portal vein, which carries venous blood from the small intestine, pancreas, and spleen.
? Thus the liver is directly in the pathway that conveys materials absorbed in the intestine. This gives the liver the first exposure to metabolic substrates and nutrients; it also makes the liver the first organ exposed to noxious and toxic substances absorbed from the intestine.
? One of the major roles of the liver is to degrade or conjugate toxic substances to render them harmless. It can, however, be seriously damaged by an excess of such substances.
? Each liver cell has both exocrine and endocrine functions.
? The exocrine secretion of the liver, called bile, contains conjugated and degraded waste products that are delivered back to the intestine for disposal. It also contains substances that bind to metabolites in the intestine to aid absorption.
? A series of ducts of increasing diameter and complexity, beginning with bile canaliculi between individual hepatocytes and ending with the common bile duct, deliver bile from the liver and gallbladder to the duodenum.
? The endocrine secretions of the liver are released directly into the blood that supplies the liver cells; these secretions include: albumin, nonimmune _?- and ?-globulins, prothrombin, and glycoproteins, including fibronectin. Glucose, released from stored glycogen, and triiodothyronine (T3), the more active deiodination product of thyroxine, are also released directly into the blood.