Chapter 6 life process class 10

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 Nutrition in Humans 

The nutrition in humans beings takes place through human digestive system. 

The human digestive system consists of the alimentary canal and its associated glands. The alimentary canal has following parts in sequence:  mouth, buccal cavity, oesophagus, stomach, small intestine and large intestine. 
The human alimentary canal is about nine metres long tube, extending from mouth to anus. The glands associated with the digestive system are salivary glands, liver and pancreas. 




The various steps of Nutrition in humans are:

1. Ingestion:   
In humans, a special organ for the ingestion of food is present which is called mouth.

2. Digestion:
In humans the digestion of food begins in the mouth itself. Mouth leads to buccal cavity which contains teeth ( incisors, canines, premolars & molars). 
The teeth help in physical digestion. The buccal cavity receives saliva from three pairs of salivary amylase.
The human saliva contains an enzyme called salivary amylase which digests starch into maltose sugar. The digestion of carbohydrate starts in the buccal cavity itself. Buccal cavity opens into a small funnel shaped Pharynx, 
Which leads to long tube called oesophagus.
Oesophagus opens into stomach which is J- shaped and is present on the left side of abdomen.
The food is churned in the stomach for about three hours. The wall of stomach contains branched and tubular gastric glands.
These glands secrete the gastric juice. 
These glands secrete Hydrochloric Acid, protein-digesting enzyme called pepsin and mucus. 

3. Absorption 

After digestion the molecules of food becomes so small that they can pass through the walls of the small intestine and goes into blood . This is called absorption. Villi present on the surface of small intestine increase the total absorption surface thus facilitating the process of absorption.

4. Assimilation

The blood carries digested and dissolved food to all parts of the body where it becomes assimilated as the part of cells. Assimilated food is used by the body cells for obtaining energy as well as for growth and repair of body.

5. Egestion

A part of food which we eat cannot be digested by our body. This undigested food cannot be absorbed by small intestine. This then passes from small intestine to large intestine. The first part of large intestine, colon absorbs most of the water from this undigested food. This undigested food becomes solid. The rectum stores this food for sometime. This undigested food is passed out through anus as faeces.

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