Nutrition in human beings

 ■ INGESTION = the human beings have a special organ for the ingestion of food. It is called mouth.

■ DIGESTION = the mouth cavity or buccal cavity contains teeth , salivary gland ,and tongue. 10 feat cut the food into smaller pieces , chew and grind it. The celebrity gland in our mouth produce saliva. Our tongue helps in mixing The Saliva with food. The salivary gland helps in chemical digestion by secret enzymes. That is salivary amylase which is digest the starch present in food into sugar. The slightly digested food in the mouth is swallowed bite the tongue and goes down the food pipe called Oesophagus , when the slightly digested food enters the food pipe ,the walls of food pipe start contraction and expansion movement that is called Peristalic movement.

The food is further digested in the stomach. It is Churned in the stomach for about three hours. During this time , the food breaks down into still smaller pieces and forms a semi solid state. The stomach wall contains three tabular glands in its wall. The glands present in the walls of the stomach secrete gastric juices. The gastric juice contains three substances : HCL , the enzyme pepsin and mucus. In the acidic medium , the the enzyme pepsin begins the digestion of proteins present in food to form smaller molecules. A function of HCL is that it kills any bacteria which may enter the stomach with food. The mucus helps to protect the stomach wall from its own secretion of HCL. The exit of food from stomach is regulated by a ' Sphincter muscle ' which releases it in small amounts into the small intestine.

The small intestine is the largest part of the alimentary canal. It is about 6.5 metres long in an adult man. The small intestine received the secretion of two glands : liver and pancreas. 

• Liver secretes bile which is a greenish yellow liquid , normal is stored in the gallbladder. It is the alkaline and contain salt which helps to break the fats present in the food. Thus , the bile performs two functions : (1.) Makes the acidic food coming from the stomach alkaline so that pancreatic enzyme can act on it.

(2.) Bile salt breaks the fats present in the food into small globules making it easy to digest.

• pancreas is beneath the stomach secrets pancreatic juice which contains digestive enzymes like pancreatic amylase which breakdown the starch. The trypsin digest the proteins and the lipase break down the emulisified fats.

The walls of small intestine contains glands which secret intestinal juice which complete the digestion of complex carbohydrates into glucose , proteins into amino acids and fats into fatty acid and glycerol.

■ ABSORPTION = after digestion , the molecules of food became songs so small that they can pass through the walls of the small intestine and go into our blood which is called absorption.

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

■ EGESTION = the undigested food passes from the small intestine into large intestine where the walls absorb most of the water from the undigested food. After that the food is passed out and known as egestion.

...I hope this helps you to understand nutrition in human beings...

••!!Thankyou!!••