Question

Answer briefly:
(a)Why are villi present in the intestine and not in the stomach?
(b)How does pepsinogen change into its active form?
(c)What are the basic layers of the wall of the alimentary canal?
(d)How does bile help in the digestion of fats?

Answer 1

The process of digestion of proteins is initiated within the stomach and terminates within the small intestine. The digestive juices that are produced within the gastric glands found on the walls of the stomach are mentioned as gastric juice. The food that comes into the stomach changes acidic when it gets mixed with this gastric juice.

Complete answer:
(a) Within the small intestine, the presence of villi causes a rise within the area for further efficient absorption of food. Since absorption of food mainly occurs within the small intestine, villi are found to be present within the intestine and not within the stomach.
(b) Pepsinogen is accumulated within the stomach walls and is a precursor of pepsin. Pepsinogen is converted into pepsin by the action of acid. Hence, the activated sort of pepsinogen is pepsin.
(c) The essential layers of the walls of the alimentary tract are four, namely:
Serosa – The outermost layer of the human alimentary tract, it consists of a fine layer of secretory epithelial cells with a couple of underlying connective tissues.
Muscularis– it's a layer of thin, smooth muscles that are arranged into an outer layer that's longitudinal and an inner layer that's circular
Sub-mucosa – it's a layer of loose connective tissue that contains the subsequent – lymph vessels, nerves, and blood. The submucosa supports the mucosa.
Mucosa– it's the innermost lining of the lumen of the alimentary tract which is chiefly involved within the processes of absorption and secretion.
(d) Bile brings about the digestion of fats. It’s a digestive fluid that's produced by the liver and accumulated within the gallbladder. The bile juice contains bile salts like biliverdin and bilirubin which disintegrate large fat globules into smaller globules for pancreatic enzymes to act on them easily. The phenomenon is termed as emulsification of fats. The bile juice is additionally known to form the medium alkaline and to activate lipase.

Note: Carbohydrates are digested in regions of the alimentary tract, the intestine to be specific and within the mouth. When the food enters the mouth, it gets mixed with the saliva produced by the salivary glands. The salivary glands include salivary amylase, which is a digestive enzyme, responsible for disintegrating starch into sugar at the pH level, 6.8.