Tuesday, 7 April 2020

DIGESTIVE SYSTEM

DIGESTIVE SYSTEM
 The process of converting food into energy giving susbstances is carried out by this system.
1. Buccal Cavity
 In the mouth salivary glands secrete saliva which contains the enzyme ptyalin.
 Also contains Lysozyme which kills bacteria
 Teeth: They are produced in two sets temporary and permanent. The teeth are of four types: Incisors, Canines, Premolars and Molars Structure of a Tooth:
 It is covered by a shining material called Enamel.
 Enamel is the hardest substance in the human body. Dental Formula:
 2123/2123. This means that there are 2 incisors, 1 canine, 2 premolars and 3 molars in half of the upper jaw and exactly the same arrangement in half of the lower jaw. i.e. 32
 The premolars and the molars are called the grinding teeth. The last molars are called the wisdom teeth.
 Linked with pharyns.

Pharynx
 Trachea opens into pharynx through an aperture called Glottis. It also receives the opening of the Eustachian tubes from the middle ear through an aperture called Gullet.

Oesophagus
 25 cm long tube.
 Leads to stomach

Stomach
 In stomach, the food is called chime.
 Has 3 parts: Fundus, Cardiac and Pyloric
 It is a warehouse, where food can be stored to await the main process of digestion.
 Gastric juices produced in the stomach help in digestion of food. Also contains HCl which kills bacteria and provides acidic medium.

Small intestine(Duodenum + Jejenum + Ileum)
 Here the food from the stomach is mixed with bile (from liver) and pancreatic juice (from pancreas) and moves forward by peristaltic movement.
 Duodenum receives the bile-pancreatic duct formed by the union of bile duct and pancreatic duct.  Bot jejunum and ileum have numerous fingurelike projections called the villi.
 Bile doesn’t take direct part in digestion of fat, it just makes the food alkaline.

Large Intestine (Caecum+colon + Rectum)
 It receives undigested material from the small intestine and absorbs water.
 Cellulose digestion takes place in it.
 Vermiform appendix is a part of caecum, which produces antibodies.

TONGUE
 Saliva, secreted by the salivary glands, is mixed with the chewed food by the tongue.
 Tongue also contains taste buds due to which we sense bitter, sour, salty or sweet taste.

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