Transcript Presentation1x

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There are two types of digestion which occur
in the body.
Mechanical digestion is when the teeth and
muscles of the stomach brake down the food
so that it can be absorbed by the body.
Chemical digestion is when enzymes and
acids within the mouth, stomach, and small
intestine brake down food into small
molecules so that it can be absorbed.
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digestion begins in the mouth where food is
mechanically broken down by the teeth as they
chew.
Saliva contains digestive enzymes such as salivary
amylase, which aids in the chemical breakdown of
food. It also contains mucous,
a glycoprotein which helps
soften the food into a bolus
(ball of chewed and moistened
food) which aids with
swallowing.
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The oesophagus is an organ in vertebrates
which consists of a muscular tube through
which food passes from the mouth to the
stomach.
During swallowing food
passes from the mouth into
the oesophagus and travels
via peristalsis to the
stomach.
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Stomach churning has the effect of assisting the
mechanical disassembly which began in the mouth.
Pepsin and other digestive enzymes work in the
stomach to chemically break down the food into
small molecules.
Food in the stomach is
in semi-liquid form,
which upon completion
is known as chyme.
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The small intestine in an adult human measures on
average about 5 meters.
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The small intestine is where most chemical digestion
takes place.
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Most of the digestive enzymes that act in the small
intestine are pancreatic enzymes secreted by the
pancreas and enter the small intestine
via the pancreatic duct. Bile
created in the liver is also
secreted into the small
intestine by the gall
bladder, It helps to break
down fat.
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Small, finger-like structures called villi, each of which is
covered with even smaller hair-like structures called
microvilli improve the absorption of nutrients by
increasing the surface area of the intestine.
Blood containing the
absorbed nutrients is
carried away from the
small intestine via the
hepatic portal vein and
goes to the liver for
filtering, removal of
toxins, and nutrient
processing.
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The function of the large intestine is to absorb
water from the remaining indigestible food matter,
and then to pass useless waste material from the
body.
Food products that cannot be absorbed into the
body, such as cellulose,
are mixed with other
waste products from the
body and become hard
and form concentrated
faeces.
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Mechanical digestion
Chemical digestion
Salivary amylase
Mucous
Bolus
Digestive enzymes
Chyme
Pancreatic enzymes
Bile
Villi and microvilli