HUMAN DIGESTIVE SYSTEM

HUMAN DIGESTIVE SYSTEM

DIGESTION IN HUMANS 

The process in which the complex  food  materials are  broken down into simpler ones by the action of enzymes and then absorbed in the blood is called digestion.
In humans ,the process of digestion is carried out by the different organs which makes up a long tube called alimentary canal. It starts from mouth and ends with anus.
There are different gastric glands associated with the digestive system such as liver , pancreas, salivary glands etc which secrete their juices to help in digestion.

THE PROCESS OF DIGESTION:

The food after entering into MOUTH 
is cut,teared and broken down into small pieces by the teeth . A digestive juice  called saliva is secreted by the three pairs of salivary glands . Two pairs of these sallivary glands are present near the jaws and one pair is present below the tongue. Saliva has an enzyme called salivary amylase or ptyalin,which helps in breaking down the complex carbohydrates into simple sugar,maltose. The tongue helps in mixing of food thoroughly with the saliva. This process of chewing,cutting and mixing of food with saliva is called" mastication" . After mastication ,the food is changed into hard solid mass called ' bolus'.




Now the food enters into next part of the digestive system called OESOPHAGUS.


The food is passed through the oesophagus by wave like movement called peristaltic movement and enters into STOMACH.


In the stomach ,HCl and gastric juices are released . The HCl Kills the germs and pathogens and also render the stomach condition,acidic which helps in protein digestion. The gastric juices has pepsin enzyme which breaks down the proteins Into peptones.  The food now has changed into slurry mass with porridge like consistency . It is now called as ' chyme'. The pyloric sphincter present in the stomach helps in controlling the passage of food into SMALL INTESTINE so that only small fraction of food enters into intestine.



The SMALL INTESTINE is the longest part of alimentary canal. It recieves the secretions from liver and pancreas . The liver secreted it's digestive juice called, Bile which does not have any enzyme. The bile converts the fats into simpler fatty acids and glycerol. This process is called " emulsification of fats". 
The pancreatic juice has trypsin ,lipase and amylase enzymes which brings out the complete digestion of carbohydrates, proteins and fats. These juices makes the condition of intestine alkaline hence rendering complete digestion of carbohydrates which was stopped in mouth.  Now all the digested food products are ready in the intestine to be absorbed in blood . This process is called" assimilation" .The inner linings of small intestine us folded into numerous small finger like projections called " microvilli" which are rich in blood and lymph vessels. The villi increases the surface area for absorption of digested food in intestine. This process of absorption of digested by the villi in intestine is called " absorption".


After absorption, the undigested food now enters into LARGE INTESTINE. The water present in the Undigested food is absorbed in large intestine, and the remaining undigested food material which is a hard solid mass called faeces is stored temporarily in RECTUM.  When rectum gets filled up with the faeces, our body expells it out  from an opening called  ANUS. This process of expelling of waste materials from our body is called " defeacation".






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