Name: Digestive System in Humans
Uploaded: 2019-07-19
Duration: 9 min 13 s
Description: The human digestive system consists of the gastrointestinal tract plus the accessory organs. Digestion involves the absorption and assimilation of food.

Question

Explain how food gets digested and absorbed in the human digestive system.

Accepted Answer

Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed by the cells of an organism.

(i) Mouth: Digestion begins in mouth. Teeth cut the food into small bits. Saliva digests starch in food and softens the food to pulp. Tongue helps to mix the food with saliva and convert food into bolus.
(ii) Oesophagus: Wall of oesophagus contracts and transports food from mouth to stomach.
(iii) Stomach: It is a big muscular bag which secretes digestive juice. Hydrochloric acid in digestive juice kills germs and enzyme pepsin breaks protein to amino acids. In stomach food get converted into a semi-fluid, chyme.

(iv) Small intestine: Secretions from liver and pancreas act on the food in small intestine. Bile helps in breaking large fat molecules into tiny droplets. Pancreatic juice helps in digestion of starch and protein. Intestinal juice acts on starch, protein and fat and completes the digestion. Villi in small intestine absorb these digested nutrients into the blood vessels.

Absorption in the small intestine:

The part of the digestive system where absorption takes place is in the intestine. The small intestine is specially structured for maximising nutrient absorption.

The internal tissue of the small intestine is lined with villi, which are tiny finger-like projections that are covered with even smaller projections, called microvilli.

The digested nutrients pass through the villi of the intestine by diffusion or special transport proteins.

Amino acids, minerals, water-soluble vitamins, and monosaccharides are transported from the intestinal cells into the blood capillaries, but the much larger emulsified fatty acids, fat-soluble vitamins, and other lipids are transported first through lymphatic vessels, which then meet up with blood vessels.

Absorption in the large intestine:

Any food that is still incompletely digested along with the indigestible fibre content of the food moves from the small intestine to the large intestine through the ileocecal sphincter.

The main function of the large intestine is to reabsorb water, minerals, such as sodium and potassium.

Explain how food gets digested and absorbed in the human digestive system.

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