3d Medical Animation
Stomach inside 3d man model created by medical-animation-studio.com
The digested food can now pass into the blood vessels in the wall of the intestine. This process is called absorption. The inner walls of the small intestine have thousands of finger like outgrowths called villi (singular villus). The villi increases the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The suface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by our body. This is called assimilation. The food that remains undigested and unabsorbed passes into the large intestine. The digestion of proteins into peptides and amino acids principally occurs in the stomach but some also occurs in the small intestine. The small intestine is where the most chemical digestion takes place:
* peptides are degraded into amino acids. Chemical breakdown begins in the stomach and is further broken down in the small intestine. Proteolytic enzymes, trypsin and chymotrypsin, which are secreted by the pancreas cleave proteins into smaller peptides. Carboxypeptidase, which is a pancreatic brush border enzyme, splits one amino acid at a time. Aminopeptidase and dipeptidase free the end amino acid products.
* lipids (fats) are degraded into fatty acids and glycerol. Pancreatic lipase is secreted here. Pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides. Pancreatic lipase performs its job with the help of the salts from the bile secreted by the liver and the gall bladder. Bile salts attach to triglycerides which aids in making them easier for pancreatic lipase to access. This occurs because the lipase is water-soluble but the fatty triglycerides are hydrophobic and tend to orient towards each other and away from the watery intestinal surroundings. The bile salts are the "middle man" that holds the triglycerides in the watery surroundings until the lipase can break them into the smaller components that are able to enter the villi for absorption.
* carbohydrates are degraded into simple sugars (e.g., glucose). In the small intestine pancreatic amylase breaks down carbohydrates into oligosaccharides. Brush border enzymes take over from there. The most important brush border enzymes are dextrinase and glucoamylase which further break down oligosaccharides. Other brush border enzymes are maltase, sucrase and lactase.
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