Digestion

DEGESTIVE SYSTEM

What is digestion?
Digestion is the process of breaking down food so that it's small enough to be absorbed and used by the body for energy or in other bodily functions.Digestion involves a number of different stages. The first phase is known as the cephalic (head) phase. It starts before food has even entered your mouth. The sight, smell, taste or even the thought offood will activate saliva in the mouth as well as digestive juices, which contain enzymes to break down food.
Once food is in the mouth, the tastebuds begin determining the chemicals within the food viatheir nerve endings, in order to give you the taste sensations of salt, sweet, sour or bitter. As your teeth chew and grind the food, breaking it down, it's mixed with saliva
After the food has beenswallowed, it's carried down the oesophagus (a muscular tube) towards the stomach. The oesophagus can contract and relax in order to propel the food onwards, and each mouthful of food takes about sixseconds to reach the stomach once swallowed
The stomach mixed the food with the stomach's acidic digestive juices to kill some bacteria and breaks down the food into proteins, that are found in inmeat, fish, eggs…
Food can stay in the stomach for a few minutes or several hours in the gastric phase where numerous acids and enzymes are released. When the food has been churned into a mixtureknown as chyme, the pyloric sphincter opens and chyme passes gradually into the small intestine.
Digestion and absorption of fats, protein and carbohydrates occurs in the small intestine. Threeimportant organs are involved:
1. The gall bladder provides bile salts that help to make fats easier to absorb.
2. The pancreas provides bicarbonate to neutralise the acidic chyme from the stomach,and also produces further digestive enzymes.
3. The intestinal wall contains cells that make up the wall of the small intestine. These cells help to neutralise the acid and also produce enzymes to...