Question

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

Answer 1

Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the bloodstream.

Digestion of food occurs in the following ways in:

1. Mouth - The mouth contains teeth, which crushes the food into small particles. Salivary glands present in the mouth secretes saliva which moistens the food. It also contains enzyme salivary amylase, that acts as

Starch$\to$ Maltose

in the presence of Ptyalin or Salivary amylase.

2. Stomach - Gastric glands are present in the wall of the stomach which releases the following secretions:

• Hydrochloric acid - To make the medium acidic for the action of enzyme pepsin.
  
• Mucus - To protect the inner lining of the stomach from the action of an acid.
  
• Pepsin - A protein digesting enzyme.
  

Proteins$\to$Peptones & Proteoses

in presence of Pepsin.

The wavelike muscular contractions in tubular structures, especially organs of the digestive system such as the oesophagus and the intestines. Peristalsis is characterised by alternate contraction and relaxation, which pushes ingested food through the digestive tract towards its release at the anus.