Digestive process?someone please explain
Posted by easyericlife
It is a very broad question.
Basically we start digesting in our mouths by chewing our food and soaking it in saliva which helps to break down starches and lubricate our food so it travels easier. Next it goes down the esophagus to the stomach where our bodies acids and chemicals break down our food further Some things are actually absorbed in the stomach. In the small intestine many more chemicals are added to help our body use the food we have eaten. The large intestine is where most of our food is absorbed. the waste is allowed to pass to the colon where it is expelled from the body
Posted by AT
The above person is generally correct, EXCEPT the stomach does most of the digesting. The small intestine does most of the absorbing. The large intestine is mainly for excretion of things that could not be absorbed or digested. There is little or no digestion or absorption in the large intestine.
Posted by Revathi P
The digestive system starts the process of breaking down polysaccharides in the mouth through the introduction of amylase, a digestive enzyme in saliva. The high acid content of the stomach inhibits the enzyme activity, so carbohydrate digestion is suspended in the stomach.
Upon emptying into the small intestines, potential hydrogen (pH) changes dramatically from a strong acid to an alkaline content. The pancreas secretes bicarbonate to neutralize the acid from the stomach, and the mucus secreted in the tissue lining the intestines is alkaline which promotes digestive enzyme activity. Amylase is present in the small intestines and works with other enzymes to complete the breakdown of carbohydrate into a monosaccharide which is absorbed into the surrounding capillaries of the villi.
Nutrients in the blood are transported to the liver via the hepatic portal circuit, or loop, where final carbohydrate digestion is accomplished in the liver. The liver accomplishes carbohydrate digestion in response to the hormones insulin and glucagon. As blood glucose levels increase following digestion of a meal, the pancreas secretes insulin causing the liver to transform glucose to glycogen, which is stored in the liver, adipose tissue, and in muscle cells, preventing hyperglycemia. A few hours following a meal, blood glucose will drop due to muscle activity, and the pancreas will now secrete glucagon which causes glycogen to be converted into glucose to prevent hypoglycemia.
In the discussion of digestion of carbohydrates; nouns ending in the suffix -ose usually indicate a sugar, such as lactose. Nouns ending in the suffix -ase indicates the enzyme that will break down the sugar, such as lactase. For example: lactose, sugar found naturally in milk, is digested by lactase resulting on a less complex molecule, a monosaccharide.
Phases of digestion
Cephalic Phase - This phase occurs before food enters the stomach. Sight and thought stimulate the cerebral cortex. Taste and smell stimulus is sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve.
Gastric Phase - This phase takes 3 to 4 hours. It is stimulated by distention of the stomach and alkaline pH (raised pH).
Distention activates long and myentric reflexes. This activates the release of acetylcholine (ACh). This in turn stimulates the release of more gastric juices. Chemical stimulation is triggered by alkaline conditions and partially digested food. This triggers G cells to release gastrin. Gastrin activated HCl secreting cells. (* notes proteins act as a buffer tying up Hydrogen ions. This causes the normal acidic conditions in the stomach to become more alkaline. HCl release is triggered by 3 chemicals acetylecholine (ACh), gastrin and histamine.
Intestinal Phase - This phase has 2 parts, the excitatory and the inhibitory. Partially-digested food fills the duodenum. This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activates sympathetic fibers (causing the pyloric sphincter to tighten to prevent more food from entering), and inhibits local reflexes.
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