DIGESTIVE SYSTEM

DIGESTION

Digestion is a process of nutrition by which the larger and complex food materials are converted into smaller and smaller food particles which are easy to absorb.

The digestive system includes the alimentary canal and the associated glands.

Ingestion: the intake of food.

Egestion: passing out of the unabsorbed food material.

                     

Various parts of digestive system are as follows-

1. Buccal cavity

2. pharyngeal cavity

3. oesophagus

4. stomach

5. intestine

The process of digestion proceeds in the following ways:

1.          In mouth- food is broken down, masticated and mixed with saliva.

2.          Pharynx- muscles in the pharynx push the food into the oesophagus.

3.          Oesophagus- It is an organ which consists of a muscular tube through which food passes from the pharynx to the stomach. Due to the rhythmic contraction and relaxation of muscles the bolus travels down to the stomach.

4.          In stomach- Many  gastric acids and juices are produced in the stomach. The mechanical churning takes place in the stomach through the action of peristalsis. This allows food to further mix with the digestive enzymes.

5.          Small intestine – It is a highly coiled structure and about 7.5 m long. As the small intestine receives food from the stomach, the digestive juices from the liver and the pancreas are mixed into it.

6.          Liver-It is the largest gland of the human body. It secretes bile juice which emulsifies the fat.

7.          Pancreas- It is located just below the stomach. It secretes pancreatic juice which breaks down carbohydrates, proteins and fats.

THE FOOD TAKEN IS NOW DIGESTED AND READY TO BE ABSORBED INTO THE BLOOD

Absorption of food into the small intestine- The inner wall of the small intestine have finger like projections called villi which have a network of thin blood vessels close to its surface. The villi increases the surface area of absorption and absorbs the food materials which are digested. The digested substances which are absorbed now are transported through the blood stream to different organs in the body and are used to build complex substances like proteins.

8.      Large intestine- The unabsorbed and undigested food  goes into the large intestine. It absorbs water and some salts from the undigested food and passes it to the rectum.

9.          Rectum and anus- Here it remains as the semisolid faeces which is further removed by the anus.