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Preksha Dhyana :
complicated movements, involving operation of reflex mechanisms to ensure that the food will go where it is meant to. First the soft palate rises blocking off the nose and prevent food from entering the nasal cavity. Both the aesophagus and trachea open into the mouth. The valve called epiglottis guards the trachea during the swallowing process, preventing the food from entering the trachea. However, sometimes, inadvertently, this automatic guarding mechanism may fail and the portion of the food may enter the trachea, which is usually thrown out by a typical fit of coughiag. If, however, a piece of food gets lodged into the trachea, it creates hazard to life and must, therefore, be removed quickly. Once the food enters the aesophagus, it is propelled down to the stomach by alternate waves of contraction and relaxation of the muscular tube.
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3. The Stomach
The food has now reached the second processing station of the tract. The muscular collapsible bag called stomach is tucked up in the abdomen at the lower rib-line under the diphragm and liver, and resembles a deflated balloon when empty. Its size and shape vary depending on how full it is. Its average size is about 22 cms. in length. When full, it slants across the body, big at the top and small at the bottom. Its capacity is two to three pints. It retains food for several hours, during which time partial digestion of protein takes place. Like the mouth, the stomach performs its function by both mechanical and chemical actions. The muscular contractions of the stomach act, like a churn and mix food thoroughly with the digestive juices. They toss, turn and mix the stomach contents, gradualy macerating the food materials mixing them with the acid gastric juice and converting them to a semi-fluid mixture. The lining of the stomach contains 35 million gastric glands which secrete four to five pints (2 to 3 litres) of gastric juice per day. Gastric juice contains mucin, hydrochloric acid and enzymes pepsin (the main component) and rennin.1 Hydrochloric acid is very important in digestion as it activates enzymes (biological
1. Infants and children whose main diet is milk have a special need for the abilities of rennin. It is not a very important component in the dault.
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