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:8: The Digestive System
Energy is essential to maintain such vital funcţions and processes as breathing, blood circulation and brain function. It is derived from foodstuffs which can be divided into several classes. Most of the food for human consumption is derived from vegetables and animals. Since they have already built up the complex molecules of proteins, carbohydrates and lipids (fats). Food materials cannot be utilised by the tissues until they have been broken down to smaller components and turned into a soluble form in order to reach the cells through the process of digestion. The digested materials can then be absorbed and sent to the tissues for production of energy. Digestive Processes
Two types of actions take place in various digestive organs:
(i) Mechanical actions
(ii) Chemical actions Mechanical Actions. Grinding, mixing and churning the food play an important part in digestion. Mere mechanical actions are, however, not enough. They move the food materials along, moisten and liquefy them and pulverize them and thus prepare the way for chemical actions of the digestive enzymes in various organs.
Chemical Actions. They convert the large and complicated molecules of the foodstuff to smaller simpler units so that they can be extracted from the digestive organs by the blood vessels, sent into the blood stream and can pass through cell membranes for assimilation by the tissues. Water, mineral oils and vitamins do not undergo chemica: action in order to be absorebed.
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