Question

What is digestion? Explain the process of digestion in the mouth cavity and stomach. Add a note on peristalsis.

Answer 1

Hint: We take food in by ingesting them. In order to retrieve the nutrients of food, we need to digest it. The process by which complex food is broken down into simpler forms is called digestion.

Complete answer:
Digestion can be defined as the mechanism by which food is broken down into smaller and simpler substances that the body can readily absorb and assimilate. It includes food degradation, both mechanical and enzymatic. In the mouth, digestion is initiated. To make it easier to chew, the food is ground up in the teeth and moistened with saliva. Saliva also has a special chemical that begins to break down carbohydrates into sugars and the chemical is called amylase. Muscular contractions of the oesophagus massage the ball of food down into the stomach until swallowed.
The food moves through the stomach via a sphincter. It is combined with gastric juices here. A muscular bag is the stomach and it churns the food to help break it down both mechanically and chemically. The inactive enzyme proenzyme pepsinogen on exposure to hydrochloric acids converted into an active pepsin enzyme which converts proteins into peptides the mucus present in stomach helps in lubrication and also prevents the stomach lining on exposure to acid. The food is then forced into the first portion of the small intestine, called the duodenum, by a second sphincter.

Note:
The saliva is mixed with food in the mouth and forms a ball-like shape and then passes into the food pipe by peristalsis. Peristalsis is a series of muscle contractions and relaxations that occur to drive through food and waste products along the path of the intestinal tract.