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What is the process of digestion?
Digestion has 4 key stages, “ingestion, mechanical and chemical breakdown of food, nutrients
absorption and elimination of indigestible food”, the first stage is ingestion which is the
process of putting food into the buccal/oral cavity, once food enters the buccal cavity, salivary
glands which are located at the roof of the buccal cavity release salivary amylase, the saliva
released wraps around the food and the slippery texture eases the swallowing of the food as it is
now slippery, the enzyme amylase is released to breakdown starch, this is known as chemical
digestion. The food is then chewed by the teeth and is broken down physically, this is called
mechanical digestion as the food is being broken down physically rather than chemically,
already we have had both types of digestion and we’re only on the first stage. The food is
chewed up and is turned into bolus which is a ball of food, the chewed up bolus is then pushed
to the back of the buccal cavity by the tongue and goes down the 27cm long oesophagus via the
process of peristalsis. The second stage is now beginning, the bolus of food reaches the stomach
via the oesophagus, the muscular walls of the stomach churn the food into Chyme, hydrochloric
acid is produced to kill any bacteria that has travelled with the food and to make the
environment acidic, an enzyme called pepsin is released in order to breakdown the food into
smaller food molecules. During this time, the liver produces a liquid called Bile and transports
it to the Gallbladder where it is stored until it’s time for it to be used, when that time arrives,
the gallbladder sends the bile to the bile duct and from there it is secreted to the small intestine
for the third stage of digestion which is absorption. The chyme that is currently in the stomach
travels down to the small intestine and combines with the bile. From there, the bile travels to
the ileum, the ileum carries out absorption, it absorbs all necessary nutrients from the bile and
takes it into the bloodstream so that the cells of the body can be fed, this is also called
assimilation. Unnecessary fluid is still left in the small intestine, consisting of fats and water…
the unwanted fluid carries on into the large intestine and water is absorbed, then the fluid is
transported to the colon and from there it is secreted to the rectum, the rectum sends a
message to the brain that the fluid which is now called stool must be released, the stool then
travels to the anus and is excreted/released which is the fourth and final stage of digestion,
elimination.
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