Download The Digestive System

The Digestive System
• The digestive system is a group of organs
that work together to digest food so that
it can be used by the body
• The digestive tract is a series of tubelike
organs that include your mouth, pharynx,
esophagus, stomach, small intestine,
large intestine, rectum and anus
• The liver, gall bladder, pancreas and
salivary glands are part of the digestive
system, but food does not pass through
these organs
Breaking Down Food
• Digestion is the process of breaking down
food into a form that can pass from the
digestive tract to the bloodstream
• Two types of digestion – mechanical and
chemical
• Mechanical digestion – the breaking, crushing
and mashing of food
• Chemical digestion – large molecules are
broken down into nutrients
• Enzymes – substances that break down larger
molecules into smaller units
Nutrients
• Three major nutrients – carbohydrates,
proteins and fats – make up most of the
food you eat
• Enzymes break some nutrients into
smaller particles that the body can use
• For example – proteins are too big to be
absorbed into the bloodstream –
enzymes break them up into amino acids
which can be absorbed
Digestion Begins in the mouth
• Teeth – very important for mechanical
digestion – break and grind food – makes
smaller pieces of food easier to digest
• Saliva – made in the salivary glands
located in the mouth - contain enzymes
that begins the chemical digestion of
carbohydrates
• Esophagus – a long straight tube that
squeezes the mass of food with rhythmic
muscle contractions called peristalsis –
The Harsh Environment of the
Stomach
• The stomach is a muscular, saclike digestive
organ attached to the lower end of the
esophagus
• Continues mechanical digestion by squeezing
food with muscle contractions
• Tiny glands in the stomach produce enzymes
and acid – work together to break down food
• Stomach acid kills bacteria that might be in
food
• Food reduced to soupy mixture called chyme
The Pancreas
• Most chemical digestion takes place after the food
leaves the stomach
• When the chyme leaves the stomach, it is very
acidic
• The pancreas makes fluids that protect the small
intestine from the acid
• Pancreas – oval organ located between the
stomach and the small intestine
• Pancreatic fluid flows into the small intestine –
contains enzymes to break down chyme and
bicarbonate to neutralize acid
• Pancreas is part of the endocrine system by making
hormones that regulate blood sugar
Small intestine
• Small intestine is a muscular tube that is
about 2.5 cm in diameter
• Stretched out, it is usually about 6 m long
• Inside wall of the small intestine is
covered with fingerlike projections called
villi
• Villi are covered with tiny nutrient –
absorbing cells
• Once nutrients are absorbed, they enter
the bloodstream
The Liver
• The liver is a large, reddish brown organ that
helps with digestion
• Located toward your right side, slightly higher
than your stomach
• Liver helps make bile to break up fat
• Liver stores nutrients
• Liver breaks down toxins
• Bile that is made by the liver is temporarily
stored by the gall bladder
• Gall bladder squeezes bile into the small
intestine to break down fat droplets
The End of the Line
• The large intestine is the organ of the
digestive system that stores, compacts and
then eliminates indigestible material from the
body
• Has a larger diameter than the small intestine
(7.5 cm)
• Undigested material enters the large intestine
as a soupy material from the body
• Most of water is absorbed from the mixture
by the large intestine
• Changes the mixture to a semi – solid called
feces
• Whole grains, fruits and vegetables contain
cellulose, or fiber, that cannot be digested
• The rectum is the last part of the large
intestine – it stores feces until it can be
expelled through the anus
• It takes your sandwich about 24 hours to
make the journey through your digestive
system