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. Find out more about these processes carried out by the gastrointestinal system through this tutorial Read More.
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Intramural Research. Extramural Research. Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? This protects the chief cells, because pepsinogen does not have the same enzyme functionality of pepsin. Second, the stomach has a thick mucus lining that protects the underlying tissue from the action of the digestive juices.
When this mucus lining is ruptured, ulcers can form in the stomach. Ulcers are open wounds in or on an organ caused by bacteria Helicobacter pylori when the mucus lining is ruptured and fails to reform. Chyme moves from the stomach to the small intestine. The small intestine is the organ where the digestion of protein, fats, and carbohydrates is completed. The small intestine is a long tube-like organ with a highly folded surface containing finger-like projections called the villi.
The apical surface of each villus has many microscopic projections called microvilli. These structures, illustrated in Figure 4, are lined with epithelial cells on the luminal side and allow for the nutrients to be absorbed from the digested food and absorbed into the blood stream on the other side.
The villi and microvilli, with their many folds, increase the surface area of the intestine and increase absorption efficiency of the nutrients. Absorbed nutrients in the blood are carried into the hepatic portal vein, which leads to the liver. There, the liver regulates the distribution of nutrients to the rest of the body and removes toxic substances, including drugs, alcohol, and some pathogens.
Figure 4. Villi are folds on the small intestine lining that increase the surface area to facilitate the absorption of nutrients. The human small intestine is over 6m long and is divided into three parts: the duodenum, the jejunum, and the ileum.
The duodenum is separated from the stomach by the pyloric sphincter which opens to allow chyme to move from the stomach to the duodenum.
In the duodenum, chyme is mixed with pancreatic juices in an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme and acts as a buffer. Pancreatic juices also contain several digestive enzymes. Digestive juices from the pancreas, liver, and gallbladder, as well as from gland cells of the intestinal wall itself, enter the duodenum.
Bile is produced in the liver and stored and concentrated in the gallbladder. Bile contains bile salts which emulsify lipids while the pancreas produces enzymes that catabolize starches, disaccharides, proteins, and fats.
These digestive juices break down the food particles in the chyme into glucose, triglycerides, and amino acids. Some chemical digestion of food takes place in the duodenum.
Absorption of fatty acids also takes place in the duodenum. The second part of the small intestine is called the jejunum , shown in Figure 3. Here, hydrolysis of nutrients is continued while most of the carbohydrates and amino acids are absorbed through the intestinal lining. The bulk of chemical digestion and nutrient absorption occurs in the jejunum.
The ileum , also illustrated in Figure 3 is the last part of the small intestine and here the bile salts and vitamins are absorbed into blood stream. The undigested food is sent to the colon from the ileum via peristaltic movements of the muscle.
The ileum ends and the large intestine begins at the ileocecal valve. The appendix of humans secretes no enzymes and has an insignificant role in immunity. Figure 5. The large intestine reabsorbs water from undigested food and stores waste material until it is eliminated. The large intestine , illustrated in Figure 5, reabsorbs the water from the undigested food material and processes the waste material.
The human large intestine is much smaller in length compared to the small intestine but larger in diameter. It has three parts: the cecum, the colon, and the rectum. The cecum joins the ileum to the colon and is the receiving pouch for the waste matter.
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