The Digestive System
The Functions of the Digestive System
1. Ingestion: when food enters the mouth
2. Digestion: when food is broken down
3. Absorption: when the body absorbs
nutrients from food
4. Elimination: when the body gets rid of
wastes
Digestion
• The process that breaks down food into
small molecules so that they can be
absorbed and moved into the blood.
– Mechanical digestion: when food is chewed,
mixed and churned.
– Chemical digestion: when chemicals break
down large molecules of food into smaller
ones.
Enzymes
• Types of proteins that speed up the rate of a
chemical reaction in your body
– Amylase: made in the mouth.
• Breaks complex carbohydrates into simple sugars.
– Pepsin: made in the stomach
• Breaks proteins down into amino acids.
– Pancreas: organ located behind the stomach
• Releases several enzymes into the small intestine to
continue the break down of foods.
– Additional enzymes aid other important chemical
reactions which are essential for numerous body
functions.
Parts of the Digestive System
Digestive Tract
1. Mouth
2. Esophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum
7. Anus
Accessory Organs
1. Tongue
2. Teeth
3. Salivary
glands
4. Liver
5. Gallbladder
6. Pancreas
Functions of the Digestive Organs
Body Part
Function
Extra Info
Mechanical & Chemical digestion begins here
Contains saliva glands
Muscular food that food passes though to
stomach
Keeps food moist (25 cm long)
Peristalsis: waves of
smooth muscle contractions
that move food through the
digestive tract
Stomach
Muscular bag where mechanical and chemical
digestion take place
Hydrochloric acid helps break down food and kill
bad bacteria
Chyme: a thin, watery liquid
that food is changed into
after it has moved through
the stomach
Small
Intestine
Most digestion takes place in the duodenum, the
first section of the small intestine
Fats are broken down and stomach acids are
neutralized
Absorption of food into the body happens here
Peristalsis also continues here
Villi: Fingerlike projections
that increase the surface
area of the small intestine
so nutrients have more
places to be absorbed
Large
Intestine
Absorbs water from undigested stuff
Helps with Homeostasis
Chyme can stay in here for
as long as three days
Mouth
Esophagus
Rectum &
Anus
Control the release of semisolid wastes from the
body as feces
Functions of accessory organs
Body Part
Tongue
Teeth
Salivary
Glands
Liver
Gallbladder
Pancreas
Function
Moves food around and mixes it with saliva
Crush food into smaller pieces. Responsible for
mechanical digestion in the mouth
Supply saliva, which is a mix of water, mucus and an
enzyme that breaks down starches into sugar. There
are three sets of salivary glands near the mouth
Produces bile, which breaks down large fat particles
much like detergents break up grease
Stores bile and increases its potency before it released
into the duodenum
Produces enzymes and a digestive solution that contains
bicarbonate ions, which neutralize stomach acid. Also
produces insulin which allows glucose to diffuse into the
body’s cells
Bacteria are Important!
• Live in the organs of
the digestive tract
• Feed on undigested
materials and make
vitamins like K (assists
in clotting)
• Converts bile pigments
into new compounds
• Breakdown on
intestinal materials
produces gas