Liver
Liver is the heaviest gland in the body and is the 2 nd largest organ in the body 2/3rds of the liver is in the right half of the abdomen. It is reddish-brown in colour. The average weight of the liver is about 5 kg but weighs more in well-fed animals and tends to decrease in weight with age. The healthy liver is firm and elastic but friable. Horses DO NOT HAVE A GALLBLADDER (therefore no bile storage). The liver is composed of several components: Hepatocytes are the major functional cells of the liver and perform a wide variety of functions. They are specialized epithelial cells making up about 80% of the liver. Hepatocytes secrete bile , a yellow, brownish, or olive-green liquid which serves as both an excretory product and a digestive secretion. Bile Canaliculi are small ducts located b/t hepatocytes that collect bile produced. Through a series of ducts bile enters DIRECTLY into the small intestine.
Role and Composition of Bile
Hepatocytes secrete ~10L of bile each day. The principal pigment in bile is Bilirubin . Once aged RBCs are have gone through phagocytosis, this liberates iron, globin, and bilirubin. The iron and globin are recycled; the bilirubin is secreted into the bile and is eventually broken down in the intestine. One of its breakdown products is SterCobilin which gives feces their normal brown colour. Bile plays a role in emulsification which is the breakdown of large lipid globules into a suspension of smaller lipid globules. This provides a large area for pancreatic lipase to more rapidly accomplish digestion of triglycerides. Bile continues to flow as digestion and absorption continue within the small intestine.
Functions of the liver:
1) Carbohydrate Metabolism : important in maintaining normal blood glucose levels by breaking down glycogen to glucose and releasing it into the bloodstream. The liver can also convert certain amino acids and lactic acid along with other sugars into glucose. When blood sugars are high, the liver can convert glucose back to glycogen and triglycerides for storage. 2) Lipid Metabolism : hepatocytes store some triglycerides; break down fatty acids to generate ATP; synthesis lipoproteins which transport FAs, triglycerides and cholesterol to and from body cells; synthesize cholesterol and use it to make bile salts. 3) Protein Metabolism : hepatocytes remove a portion of the protein so that amino acids can be used to produce ATP or be converted to carbohydrates or fats. Hepatocytes also synthesize plasma proteins such as alpha and beta globulins, albumin, prothrombin, and fibrinogen.
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