Role of pancreas and liver

Question

describe the role if the liver and pancreas in the assimilation of the products of digestion 

Answer 1

Digestion of food materials especially fats is aided through the liver which produces bile ( composed of bile acids, bile pigments, phospholipids, bilirubin, cholesterol, water, and electrolytes) and pancreas secreting pancreatic juice( containing digestive enzymes and bicarbonate ions). But these digestive juices are released into the duodenum only when food reaches the duodenum from the stomach for final digestion. When digestion occurs complex food materials (macromolecules) need to be broken down into simpler forms so that digestion and absorption of nutrients occur easily.

Lipids have a hydrophobic nature that does not allow them to get mixed up with water. This makes the digestion of lipids difficult in the aqueous nature of the small intestine. So, before they enter the small intestine, they undergo a process of emulsification where they are broken down into smaller fat globules thereby increasing their surface area on which lipases can act more efficiently and enhancing easy absorption in the body. This process is supplemented by pancreatic enzymes that hydrolyze the ester bonds of triglycerides, and cholesteryl esters.  Bile salts and phospholipids act as emulsifying agents, thus playing a significant role in digestion and absorption. The lipid metabolites are then packaged into micelles. Micelles are composed of hydrophobic and hydrophilic components. The hydrophilic end faces the watery environment of the intestinal chyme and the hydrophobic end turns to the center making it inclusive of the triglycerides and other fat soluble vitamins. Micelle can squeeze easily between the microvilli of the small intestine and the moment it enters the brush border of intestinal cells; it releases the lipids by simple diffusion. After the digestion of lipids, the free fatty acids and monoglycerides that are formed are reincorporated into triglycerides forming Chylomicrons ( water soluble) which are transported through the lymphatic ducts releasing back into the circulatory system.

 The gall bladder temporarily stores and concentrates bile, so that it can be released whenever food reaches the small intestine. Pancreatic enzymes and sodium bicarbonate ions in pancreatic juice being alkaline in nature help in neutralizing the acidic nature of chyme ( acidic fluid passed from stomach to small intestine consisting of gastric juices and digested food) thus facilitating digestion and absorption.

Thus, the liver and pancreas help in the assimilation and digestion of food material mainly by secreting bile and pancreatic juices.