Draw a labeled diagram of the human digestive system. With the help of this diagram, describe the process of digestion of food in man (human).

•Mouth: Mouth is the first step in Digestion Process. Mouth is the cavity which contains tongue, teeth and salivary glands. Salivary gland, secret saliva and enzyme known as salivary amylase. Teeth chew and grind the food and tongue mixes the food with saliva so as to making the food easy to swallow. Salivary amylase digests the starch and converts it into maltose but this digestion of starch is left incomplete because of short duration of time.

•Esophagus: Food is carried from mouth to stomach through esophagus.

•Stomach: Stomach is a J-shaped organ present on the left-side of the abdomen. In stomach tubular glands are present which secretes gastric juice. Gastric juice contains hydrochloric acid, mucus and enzyme pepsin. HCl acid in stomach kills the bacteria which enters the stomach and also provides the proper medium in which enzyme pepsin can work. Mucus protects the lining of the stomach from the acid and pepsin. Pepsin in acidic medium acts on proteins and digest the proteins present in the food.

•Partially digested food is passed on to small intestine which is regulated by the sphincter.

•Small Intestine: Small intestine is about 6.5m long and is the largest part of the alimentary canal. Complete digestion of food takes place in small intestine. Small intestine receives secretions from liver and pancreas. Liver secretes bile which is responsible for converting the acidic food into alkaline so that pancreatic enzymes can work on it. Also the bile salts coverts the large fat globules into small globules so that it can be easily digested. Pancreas secretes pancreatic juice which contains lipase which digests fats, trypsin which digests proteins and amylase which digest starch. Small intestine secretes intestinal juices which have different type of enzymes which digests the carbohydrates and converts them into glucose, proteins and converts them into amino acids and fats and converts them into fatty acids and glycerol.

After the digestion of food absorption of food takes place in small intestine with the help of small finger-like projects known as villi.

•Large intestine: After absorption of food the undigested food is sent to large intestine. Here water is absorbed from the undigested food and it is again converted into solid, which is then thrown out of the body through anus in the form of waste material known as faeces.