Give an account of various parts of alimentary canal of man.

Explanation

Alimentary canal, also called digestive tract, is a pathway by which food enters the body and solid wastes are expelled out. The alimentary canal includes the mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus.
(i) Mouth : Food starts off travelling through the mouth, where it is chewed into smaller particles. Saliva in the mouth breaks down carbohydrates, and turns starch into sugar.
(ii) Oesophagus : Oesophagus is also known as food pipe. It begins from the neck and ends in the stomach. From the mouth food travels down the oesophagus, The oesophagus doesn.t play any part in the chemical breakdown of food, it only transports it to the stomach.
(iii) Stomach : Stomach is a bag-like organ. Highly muscular walls of the stomach help in churning the food. In the stomach gastric juices containing enzymes break down the food. The enzyme pepsin breaks down proteins into peptides. Lipase breaks down the fats.
(iv) Small Intestine : It is a highly coiled tube-like structure. The small intestine is longer than the large intestine but its lumen is smaller than that of the large intestine. The small intestine is divided into three parts, viz. duodenum, jejunum and ileum. The food particles move down into the first part of the small intestine (duodenum), that.s where the food is absorbed into the intestine walls. The intestine has small projections called villi, which help this process by creating more surface area for diffusion.
(v) Large Intestine : Large intestine is smaller than small intestine. Undigested food goes into the large intestine. After the nutrients have been absorbed, the rest (waste) move onto the large intestine. The large intestine transports it and sucks out the water from the waste, then the waste moves out through the anus. Other important parts of the digestive system include the liver, pancreas and gall bladder. The liver produces bile, an alkaline enzyme that breaks down the fats. Bile is stored in the gall bladder until it is needed in the small intestine for digestion. The pancreas produces parcreatic juices important for digesition.