What are the 7 steps in human digestion?

Hello Shambhavi,

The seven steps of digestion are as follows:

1. Ingestion: It is the entry of food into the mouth. Chewing breaks the food into small pieces and saliva mixes with food that can be easily passed through to the stomach through the oesophagus.

2. Propulsion: It is the rhythmic movement of food,  alternating contraction and relaxation (peristalsis) of smooth muscle along the lines of the wall of the digestive tract. This peristalsis is the forces that help in moving food in forwarding direction.

3. Mechanical Digestion: In mechanical digestion, the food is physically broken down into smaller fragments through the action of chewing (mouth), churning (stomach) and segmentation (small intestine).

4. Chemical Digestion: When food enters into the stomach the inner lining of the stomach secretes mucous, hydrochloric acid, and digestive juices. The acid makes the medium in the stomach acidic and helps the digestive juices which break down the proteins into simpler substances. The small intestine receives secretions from the liver and the pancreas to breakdown the carbohydrates, fats and proteins the digestion.

5. Absorption: The digested food passes into the blood vessels in the wall of the intestine which has thousands of finger like outgrowths. These are called as villi which increase the surface area for absorption of the digested food.

6. Assimilation: The absorbed substances are transported to different organs via the blood vessels. These substances are used to build complex substances like proteins. This is called as assimilation.

7. Egestion: The undigested and unabsorbed food enters into the large intestine where it water and some salts get absorbed from the undigested food material. The remaining waste passes to the rectum. This fecal matter is removed through anus. This is called egestion.


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