Question

Explain the process of digestion in human beings.

Answer 1

• Humans have holozoic nutrition, that means the food is consumed as a whole and the digestion occurs internally. It can be described as:

1. Ingestion of food- The food is taken in the oral cavity in the process called the ingestion. The teeth help in grinding of the food, salivary amylase helps in partial breakdown of the starch and the tongue helps in mixing the food with saliva and helps in swallowing it. The food is now called bolus.

2. Digestion- The process of break-down of complex substances into simpler substances is called digestion and it starts with the mouth where physical break-down occurs along with some chemical digestion. The bolus is swallowed in and it arrives in stomach where the digestion of proteins occurs due to presence of the enzyme pepsin. Bolus is now called the chyme. This chyme now moves into the small intestine where rest of the process of digestion will be completed. The pancreatic juice, the intestinal juice and the bile will result in breakdown of carbohydrates, fats and the rest of the proteins. The chyme is now called the chyle and it moves to the large intestine where the water is absorbed.

3. Absorption- The digested food is absorbed via the finger-like projections present on the inner surface of the small-intestine and the reach the blood stream.

4. Assimilation- The absorbed food is then used by different tissues for the energy generation. The excess food is stored as glycogen in the liver and s fats in adipose tissue.

5. Excretion- The undigested material passes from the small-intestine to the rectum of the large-intestine, from where it is removed from the body through anus.