Human Digestive System

Nutrition in Human Beings:-

Human beings are complex animals, which have a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands. The alimentary canal is divided into several parts, like oesophagus, stomach, small intestine, large intestine, rectum and anus. Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal.

• Mouth – intake of the food.

• Teeth – Chewing/grinding of food.

• Tongue – Rolling of food, tasting of food, swallowing/pushing down the food.

• Salivary glands – secrete saliva, mucus(it is a sticky, gelatinous material that lines your lungs, throat, mouth, nose and sinuses), starch is converted into glucose by saliva (Salivary amylase)

• Oesophagus – It takes the food from the mouth to the stomach by peristaltic movements (contraction and expansion of muscles of the oesophagus)

• Stomach – Gastric glands present in the stomach secrete gastric juice.

• Small intestine – it is the site of the complete digestion of carbohydrates, proteins and fats

• Walls of small intestine secrete intestinal enzyme which converts carbohydrates into glucose, fats in fatty acid + glycerol and proteins into amino acids

• It has villi (finger projection) which help in the absorption of food into blood.

• It receives the secretions of the liver and pancreas.

• The food is acidic which is made alkaline for the pancreatic enzymes to act. The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

• Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules which increases the efficiency of enzyme action

• Large intestine – it absorbs excess water and the rest of the material is eliminated from the body via the anus.