4 Stages of Digestion in Human Body are provided and clearly explained in this article. You will find the article helpful and informative.
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1. Based on fact, saliva is alkaline and contains a digestive enzyme called ptyalin which splits some of the cooked starch in the food into dextrin and maltose.
This is from the mouth that the food is passed down to the gullet or esophagus. Contraction of the muscles in the wall of the gullet forces the food along and into the stomach.
Talking about the stomach when it comes to digestion, in the upper part of the stomach the food is squeezed and churned up by contraction of the muscles in the wall and is mixed more thoroughly with the saliva.
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Hydrochloric acid is one of the secretions of glands in the walls of the stomach. Digestion of starch by ptyalin is arrested when the alkaline saliva is neutralized by hydrochloric acid. Another set of glands in the walls secrets an enzyme, pepsin.
The glands of young children secrete an enzyme called renin. Hydrochloric acid, as well as neutralizing the alkaline saliva and stopping the action of ptyalin, kills many of the microorganisms which occur in food.
The acid and the pepsin together change insoluble protein foods into soluble peptones. Rennin when present in young children, curdles milk and separates the protein and fat of milk.
Another enzyme called gastric lipase is secreted in the gastric juice, but this enzyme is inactive in the normal acidity of the stomach and does not take any part in digestion here.
Gastric juice is poured into the stomach at the sight, smell, and taste of food. Any colorful food attractively served and prepared that has a good aroma and tastes good will excite the secretion of digestive juices and assist digestion.
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The length of time the food remains in the stomach will vary with the composition of the diet and with the individual. Carbohydrates leave the stomach most rapidly, proteins next and fats remain the longest.
Fatty foods stay in the stomach for longer and are more satisfying. Therefore, hunger does not follow a few minutes after such a meal especially when those are classes of foods rich or classified as foods containing carbohydrates.
Here, the mixture leaving the stomach is called chyme. From the stomach, the chyme passes through the pyloric sphincter into the duodenum, a U-shape tube about 10 inches long and one and a half inches in diameter.
Ducts from the gall bladder and from the pancreas pass into the duodenum. The secretion from these two glades mixes here with the partially digested food.
The secretion from the gall bladder is called bile. About one and a half pints of bile is produced daily by the liver and stored in the gall bladder.
The bile is alkaline and neutralizes the acid chyme and stops the action of gastric juices. The bile salts in the fluid emulsify the fats, which means the fat particles are called pancreatic juice.
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4. The small intestine
From the duodenum, the food enters the small intestine, a tube about 19 feet long. Waves of contraction of the muscles of the small intestine drive the food along by the action called peristalsis. More digestive juices are secreted here, these intestinal juices contain more enzymes.