Intestinal Juice. Bile juice is secreted by the gall bladder. After being secreted by the gall bladder it travels through the bile duct that opens into the duodenum. Bile juice contains bile salt that helps to emulsify fats. Fats are broken down into small globules that are easily digested by the enzyme lipase present in the pancreatic juice.
The pancreatic juice is secreted by the pancreas. It travels through the pancreatic duct that opens into the duodenum. The enzymes present in the pancreatic juice are as follows:. The walls of the ilium are made up of fingerlike projections known as villi. Villi are made of up microvilli. Therefore, ilium has a very large surface area. The main function here is to absorb Vitamin B12, bile salts, and the products of digestion. Cells lining the ilium also secrete protease and carbohydrase enzymes responsible for the final stages of protein and carbohydrate digestions.
The villi contain large numbers of capillaries which take the amino acids and glucose produced by digestion to the liver through the hepatic portal vein. Lacteals are small lymph vessels that are present in villi. They absorb fatty acids and glycerol, the products of fat digestion. The lacteals transport the fatty acids and glycerol to the lymphatic system for filtering.
The fatty acids and glycerol are combined with the blood as lymph joins blood at the right and left subclavian veins. The large intestine is mainly responsible for storing waste, reclaiming water, maintaining the water balance, and absorbing some vitamins, such as vitamin K. The large intestine is divided into the cecum, colon, rectum, and anal canal. The gastrointestinal system breaks down particles of ingested food into molecular forms by enzymes through digestion and then transferred to the internal environment by absorption.
The enzyme pepsin plays an important role in the digestion of proteins by breaking down the intact protein to peptides, which are short chains of four to nine amino acids. In the duodenum, other enzymes— trypsin, elastase , and chymotrypsin —act on the peptides reducing them to smaller peptides.
Trypsin elastase, carboxypeptidase, and chymotrypsin are produced by the pancreas and released into the duodenum where they act on the chyme. Further breakdown of peptides to single amino acids is aided by enzymes called peptidases those that break down peptides. Specifically, carboxypeptidase, dipeptidase , and aminopeptidase play important roles in reducing the peptides to free amino acids.
The amino acids are absorbed into the bloodstream through the small intestines. The steps in protein digestion are summarized in Figure Lipid digestion begins in the stomach with the aid of lingual lipase and gastric lipase. However, the bulk of lipid digestion occurs in the small intestine due to pancreatic lipase. When chyme enters the duodenum, the hormonal responses trigger the release of bile, which is produced in the liver and stored in the gallbladder.
Bile aids in the digestion of lipids, primarily triglycerides by emulsification. Emulsification is a process in which large lipid globules are broken down into several small lipid globules. These small globules are more widely distributed in the chyme rather than forming large aggregates.
Lipids are hydrophobic substances: in the presence of water, they will aggregate to form globules to minimize exposure to water. Bile contains bile salts, which are amphipathic, meaning they contain hydrophobic and hydrophilic parts. Thus, the bile salts hydrophilic side can interface with water on one side and the hydrophobic side interfaces with lipids on the other. By doing so, bile salts emulsify large lipid globules into small lipid globules.
Why is emulsification important for digestion of lipids? Pancreatic juices contain enzymes called lipases enzymes that break down lipids.
If the lipid in the chyme aggregates into large globules, very little surface area of the lipids is available for the lipases to act on, leaving lipid digestion incomplete.
By forming an emulsion, bile salts increase the available surface area of the lipids many fold. The pancreatic lipases can then act on the lipids more efficiently and digest them, as detailed in Figure Lipases break down the lipids into fatty acids and glycerides. These molecules can pass through the plasma membrane of the cell and enter the epithelial cells of the intestinal lining.
The bile salts surround long-chain fatty acids and monoglycerides forming tiny spheres called micelles. The micelles move into the brush border of the small intestine absorptive cells where the long-chain fatty acids and monoglycerides diffuse out of the micelles into the absorptive cells leaving the micelles behind in the chyme.
The long-chain fatty acids and monoglycerides recombine in the absorptive cells to form triglycerides, which aggregate into globules and become coated with proteins. These large spheres are called chylomicrons. So for vegetarians , variety is key. In addition to choosing the right protein sources, you can also adopt certain habits to help get the most out the food you eat. Protein is a vital nutrient for almost every part of your body. You can maximize the nutrients you get from protein sources by eating complete proteins and adopting certain habits, such as chewing thoroughly before swallowing.
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