Parts of the body concerned with the uptake and digestion of food and elimination of indigestible remains form the digestive system, also called ‘alimentary system’.
The human digestive system consists of an alimentary canal and many digestive glands.
The alimentary canal is a long tube with muscular walls, glandular epithelial lining, and varying diameter.
It opens out at the upper and lower ends, and most of it lies in the abdomen in a much-coiled form.
PARTS OF THE HUMAN DIGESTIVE SYSTEM
Mouth or Buccal Cavity: The mouth has teeth and tongue
The tongue has gustatory receptors which perceive the sense of taste.
Tongue helps in turning over the food, so that saliva can be properly mixed in it.
Salivary glandssecrete saliva. Saliva makes the food slippery which makes it easy to swallow the food.
Saliva also contains the enzyme salivary amylase or ptyalin. Salivary amylase digests starch and converts it into sucrose.
Teethhelp in breaking down the food into smaller particles so that swallowing of food becomes easier.
Types of Teeth
There are four types of teeth in human beings.
The incisor teeth are used for cutting the food.
The canine teeth are used for tearing the food and for cracking hard substances.
The premolars are used for coarse grinding of food.
The molars are used for fine grinding of food.
Parts of The Human Digestive System
Stomach:
Stomach is a wide, J-shaped bag-like organ. Highly muscular walls of the stomach help in churning the food.
The stomach has 4 regions: cardiac part, fundus, body and pyloric part.
The walls of the stomach secrete hydrochloric acid.
It makes the medium inside the stomach acidic.
The acidic medium is necessary for gastric enzymes to work.
The enzyme pepsinsecreted in the stomach; does partial digestion of protein.
The mucus secreted by the walls of the stomach saves the inner lining of the stomach from getting damaged from hydrochloric acid.
Functions of Stomach
The stomach serves 4 main functions: storage of food, mechanical churning of food, partial digestion, and regulation of the flow of food into the small intestine.
Small Intestine:
It is a highly coiled tube-like structure.
The small intestine is longer than the large intestine.
It is the longest part of the alimentary canal.
The small intestine is the site of the complete digestion of carbohydrates, proteins and fats. It receives the secretions of the liver and pancreas for this purpose.
The small intestine is divided into three parts, viz. duodenum, jejunum and ileum.
Liver:
Liver is the largest organ in the human body.
Liver manufactures bile: which gets stored in gallbladder.
Pancreas:
Pancreas is situated below the stomach.
It secretes pancreatic juice which contains many digestive enzymes.
Bile and pancreatic juicego to the duodenum through a hepato-pancreatic duct.
Bile breaks down fat into smaller particles.
This process is called emulsification of fat.
After that, the enzyme lipase digests fat into fatty acids and glycerol.
Trypsin and chymotrypsin are enzymes which digest protein into amino acids.
Complex carbohydrates are digested into glucose.
Small Intestine
The major part of digestion takes place in the duodenum.
No digestion takes place in jęjunum.
The inner wall in the ileum is projected into numerous finger-like structures; called villi
Digested food is absorbed by villi.
Large Intestine:
Large intestine is smaller than small intestine.
Undigested food goes into the large intestine.
Some water and salt are absorbed by the walls of the large intestine.
After that, the undigested food goes to the rectum: from where it is expelled out through the anus.