Question

5.  List all major structures and organs involved in the flow of blood through the hepatic portal system. Begin with major veins of the intestines and end with the inferior vena cava.

6.  Outline the major events occurring during the digestion and absorption of lipids. Begin with emulsified fats in the duodenum and end with absorption of micelle in lacteals

7.  Outline the major events occurring during the digestion and absorption of proteins. Begin with protein digestion in the stomach and end with absorption of amino acids in the intestinal capillaries.

Answer 1

5. Hepatic portal system is network of blood vessels which carry blood from intestine into the liver and then into venous drainage system.

The pathway of blood flow in hepatic portal system is as follows-

Firstly the arteries which are present in the intestine,stomach, pancreas and spleen combines to form hepatic portal vein and leaves the gastrointestinal region.

Now hepatic portal vein enters the liver and blood is poured into the liver sinusoids. After this, hepatic vein originates from the liver and finally joins inferior Vena Cava.

6. Lipids are digested by lipolytic enzymes.

Saliva has lingual lipase. Stomach has gastric lipase in gastric juice. Intestine has bile salts, pancreatic enzymes and intestinal lipase.

All these above enzymes digest lipids into fatty acids, cholesterol and monoglycerides.

Monoglycerides, cholesterol and fatty acid form micelles and enters the cells of intestinal mucosa by simple diffusion.

Triglycerides and cholesterol esters are coated with layer of protein, cholesterol and phospholipids to form chylomicrons. These chylomicrons enters the lymph vessels and are transferred into the blood from lymph.

7. Enzyme responsible for digestion of proteins are called proteolytic enzymes.

In stomach, pepsin converts proteins into proteoses, peptones and large polypeptides.

In intestine, pancreatic juice has trypsin, chymotrypsin and carboxypeptidase. These convert proteoses and peptones into dipeptide, tripeptide and polypeptides.

Succus entericus has dipeptidases, tripeptidases and amino peptidases. These finally converts all products into amino acids.

Proteins are absorbed in the form of amino acids from small intestine. The levo amino acids are actively absorbed by means of sodium cotransport, whereas the Dextro amino acids are absorbed by means of facilitated diffusion.