Tuesday, 31 January 2017

Describe the process of digestion of food from the mouth to the stomach The mouth

Define the following terms
 Ingestion: taking food into a living organism
 Digestion: Breaking down large insoluble food molecules into small soluble ones
 Absorption: The process by which food molecules enter the blood stream
 Assimilation: Making use of the absorbed food substances
 Egesting: Getting rid of undigested materials.

Describe the process of digestion of food from the mouth to the stomach
The mouth
Food is ingested and chewed. The teeth help to tear and grind the food into small pieces. This increases the surface area for the action of enzymes. The food is mixed with saliva which has two functions.
1. The saliva contains mucus which is a slimy substance which helps the food to be swallowed.
2. It contains the enzyme amylase which begins the digestion of starch into the sugar maltose. As food does not remain in the mouth for very long, only a small amount of starch is digested here. The food is then turned to a bollus shape by the action of the mouth and then swallowed.
This tube pushes the food to the stomach by way of rhythmic contractions. There are two sets of muscles in the oesophagus.
1. Circular muscles - these make the oesophagus narrower.
2. Longitudinal muscles - these make the oesophagus wider.
This is the way food is move all way along the alimentary canal. It is called peristalsis. The moment the food is swallowed the epiglottis closes so food isnt swallowed in the trachea.
When the food reaches the stomach gastric juice is released from the stomach lining. Gastric juice contains two substances.
1. Pepsin - an enzyme which breaks proteins down into polypeptides.
2. Hydrochloric acid - needed to activate pepsinogen to pepsin.also kills any ingested bacteria.

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