Download Digestive System

Digestive System
Digestive System
• A group of organs that work together to break down food
so that it can be used by the body.
• Digestive Tract: organs the food passes through; includes
the mouth, pharynx, esophagus, stomach, small
intestine, large intestine, rectum, and anus.
• Also includes liver, gall bladder, pancreas, and salivary
glands.
• Takes food about 24 hours to pass through the digestive
tract.
Breaking Down Food
• Digestion: the process of breaking down food into a
form that can pass from the digestive tract to the
bloodstream.
• Two types of digestion:
1. Mechanical- breaking, crushing, and mashing of
food.
1. Chemical- large molecules are broken down into
nutrients.
• Enzymes are substances that break some
nutrients into smaller particles.
• Nutrients are substances needed for energy,
growth, maintenance, and repair.
1. Carbohydrates (sugars)
2. Proteins (amino acids)
3. Lipids (fats)
Mouth
• Chewing creates smaller pieces of food that are wet
and easier to swallow.
• Teeth perform mechanical digestion. Covered in
enamel, the hardest material in the body which
protects the interior of teeth.
• Saliva that is made in the salivary glands contains
enzymes that begin chemical digestion of
carbohydrates.
Pharynx
• Tube that connects mouth to esophagus.
Esophagus
• Food is pushed by the tongue into the throat
that leads to this long straight tube.
• Esophagus squeezes the food with muscle
contractions called peristalsis (mechanical
digestion).
Stomach
• Small, muscular, saclike organ attached to the
lower end of the esophagus.
• Continues mechanical digestion via peristalsis.
• Tiny glands produce enzymes and acids that
chemically break down food.
• Stomach acid kills bacteria also.
• Food is eventually reduced into chyme, a soupy
mixture.
Small Intestine
• Muscular tube longer than you are tall! Called
“small” due to small diameter.
• Valve allows chyme to enter in small amounts.
• Most chemical digestion occurs here.
• Absorption of nutrients.
• Covered in villi which absorb nutrients that enter the
bloodstream to be delivered to cells in the body.
Pancreas
• Between the stomach and small intestine.
• Food does NOT pass through.
• Makes enzymes and bicarbonate (acid
neutralizer) that protect the small intestine.
• Also makes hormones that regulate blood
sugar.
Liver
• Reddish, brown organ located toward the right
side of the body.
• Food does NOT pass through.
• Makes bile to break up fat, stores nutrients, and
breaks down toxins.
• Detoxifies many chemicals, such as alcohol and
drugs.
Gall Bladder
• Temporarily stores the bile made by the liver.
• Bile breaks down large fat droplets so more of
the fat can be exposed to digestive enzymes.
Large Intestine
• Most of the water in the leftover chyme is absorbed
here.
• Water and indigestible materials are stored and
compacted into feces.
• Cellulose which comes from plants we eat, cannot be
digested. This “fiber” keeps feces soft and moving
through the intestines.
• Rectum stores feces until elimination.
• Anus is the opening through which the feces pass out.
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