Every organism needs food to live. There are five steps of nutrition or food intake to its usage.
- The process of taking food inside by eating or drinking.
- Making food ready for energy absorption or digestion.
- Digested food passes through food pipe and gets absorbed in body through intestines.
- Absorbed food used in the necessary and required places of human body.
- Non absorbed and non digested food comes out in form of waste from body.
Parts of Digestion System
1. Mouth - Teeth present inside the mouth cuts the food into pieces. Our salvia glands excrete salvia which softens the food, the enzyme present in salvia changes starch present in food to soluble maltose.
There are two sets of teeth: temporary (milk teeth) (20) which falls down and permanent teeth (20 and 12) come out. Out of 12 temporary teeth every jaw has three teeth on both sides to chew the food. In the end one last wisdom tooth comes out around 16-17 year. A wisdom tooth does not come out in some people. There are many types of teeth in a jaw set which are used in chewing, cutting, grinding and mixing of food.
2. Food is softened by mouth - Salvia helps in chewing the food. This is secreted by the tongue. Tongue and teeth chew the food. Mostly the push of tongue helps the food to reach the food pipe.
3. Food reaches a bag like stomach from food pipe.
4. Food stays in stomach for 3-4 hours. By this time the juice from the walls of stomach mixes with food. This gastric juice has pepsin enzyme which helps in digestion of protein. One more acid comes out from this juice called hydrochloric acid. This acid destroys any bacteria coming with the food. Food reaches small intestine from stomach.
5. Small intestine is around 7 meter long with narrow structure. It has many spiral structures. Maximum food get digested here - protein, carbohydrates, maltose, sucrose and fats are digested by many enzymes. These enzymes come out from pancreas and even small intestine. Digestion is not needed from vitamins and mineral salts there are absorbed directly in intestine.
6. Big intestine: Small intestine is connected to big intestine. Here, maximum water of the left food is absorbed.
7. Undigested food is waste which comes out if human body.