Transcript The Digestive System

The Digestive System
The Digestive System is composed of 5 main
parts. They are:
1) The Mouth
2) The Esophagus
3) The Stomach
4) The Small Intestine
5) The Large Intestine
The Mouth
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This is where digestion first begins in the
body
The teeth perform physical digestion by
breaking the food into smaller pieces
The enzyme amylase performs chemical
digestion by breaking down starch to sugar
The Esophagus
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The esophagus is a tube of smooth muscle
that connects the mouth to the stomach
It is about 25 cm long
Food moves through the esophagus by the
process of peristalsis
No digestion occurs in the esophagus
The Stomach
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The stomach is like a muscular bag – It contracts
rhythmically to mix the contents
It contains gastric juice which is a mixture of
hydrochloric acid and enzymes
The acid kills invading pathogens on the food we
eat
It has a thick mucus layer to withstand the acid
The entrance to the stomach is controlled by the
cardiac sphincter, the exit by the pyloric sphincter
The Small Intestine
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The small intestine is composed of 3 parts:
the duodenum, the jejenum, and the ileum
It is about 6m long
6 enzymes present: Erepsin and
enterokinase to digest protein; maltase,
sucrase, and lactase to digest sugars; and
lipase to digest fat
Small Intestine continued…
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The inner membrane of the small intestine
is highly folded into tiny, finger-like
projections called villi
The villi greatly increase the surface area
available for nutrient absorption
The Large Intestine
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No digestion occurs in the large intestine
The main job of the large intestine is to
reabsorb water to prevent dehydration
Other Structures Involved in Digestion
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The Liver: The largest gland in the body, the liver
produces bile to emulsify fats. It stores energy,
iron, and vitamins A, D, and B12
The Pancreas: The pancreas produces
pancreatic juice which contains 28 enzymes. This
juice also neutralizes the stomach acid to prevent
damage to the small intestine. It also produces
insulin to help regulate blood sugar
Other Structures continued…
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Gall Bladder: The gall bladder stores the
bile produced by the liver until it is ready to
be released