Download Digestive System

The Digestive
System
Coachbook, pages 67-68
Getting the Idea:
The nutrients your cells
use to produce energy
come from the food you
eat. Breaking food down
for energy also produces
wastes. Those wastes must
be removed from the body.
Two of your body
systems break food
down into usable
forms and remove
wastes products
from your body.
The Digestive System
The digestive system is the
group of organs that break
food down into molecules
that are small enough to
be absorbed by and
transported throughout
the body.
The Mouth
Digestion begins in the
mouth as your teeth grind,
crush, and break apart
your food. Breaking food
into smaller pieces is
known as
mechanical digestion.
• As you chew your food, your
tongue moves the food around
and mixes it with saliva. Saliva
moistens the food so it is
easier to swallow. Saliva also
contains an enzyme that begins
to break down starches and
sugars. An enzyme is a protein
that speeds up a chemical
reaction.
• When food has been chewed enough, it
is moved to the back of the mouth for
swallowing.
• After food is swallowed, it passes the
epiglottis, a flap of tissue that covers
the opening of the trachea to keep food
out.
• The food then moves into the
esophagus.
The Esophagus
• The esophagus is a muscular tube
that connects the mouth to the
stomach.
• Contractions of the muscles in the
wall of the esophagus push the food
toward the stomach. These
contractions are called peristalsis.
Mouth and Esophagus
Mouth
• Teeth - break up the food.
(Mechanical Digestion)
• Saliva- chemical in the
mouth that begins digestion.
(Chemical Digestion)
Esophagus
• Tube that connects the
mouth to the stomach.
The Stomach
The stomach is a muscular organ. It
continues mechanical digestion by
contracting and squeezing its
contents. Glands in the stomach
produce enzymes and acids that
continue to break food molecules
apart through chemical digestion.
Dinosaur Stomach
Small Intestine
•Food remains in the stomach for
several hours!!
•The stomach digests the food
into a liquid. This liquid then
enters the small intestine, a long,
muscular tube where the body
absorbs nutrients from food.
The Pancreas
• The pancreas is a gland that releases digestive
enzymes and other chemicals into the small
intestine.
• Some of these substances neutralize stomach
acids, which would otherwise damage the
lining of the intestine and prevent enzymes
from doing their job.
The Liver
–The liver also helps with
digestion in the small
intestine.
–The liver is an organ that
makes bile, a liquid that
helps to break down fat.
The Gall Bladder
The bile produced
by the liver is
temporarily stored
in the gall bladder.
Absorption in the Small Intestine
•Once food is digested, nutrients are
absorbed through the walls of the
small intestine.
•The walls of the small intestine have
many folds called villi, which
increase the surface area that can
absorb digested food.
Villi greatly increase the surface area of the small
intestine.
Laid out, it would be equal to the surface of a
tennis court.
Villi
•Nutrients enter the bloodstream
through the capillaries in the villi. The
blood then transports the nutrients to
all the cells of the body.
•Any undigested material left in the
small intestine is moved by peristalsis
into the large intestine.
Peristalsis
• Waves of muscle contractions
that pushes food through the
digestive tract.
The Large Intestine
• The large intestine is an
organ of both the digestive
system and the excretory
system. Its role in digestion is
to absorb water from the
undigested material.
• The large intestine also
compacts the solid wastes
that remain from undigested
food.
The Large Intestine
continued…
• The remaining material is ready for elimination from
the body.
• Rectum- a short tube that is the last portion of the
large intestine.
• Waste material is pressed into a solid form.
• Waste material exits through the anus, a muscular
opening at the end of the rectum.
Rectum
Opening
And
Closing