Download The Digestive System

The Digestive System
CA 5th Grade Science Standards:
5LS2c. students know the sequential steps of digestion and the role of
teeth and the mouth, esophagus, stomach, small intestine, large
intestine, and colon in the function of the digestive system.
Purpose of the Digestive System
The purpose of the digestive
system is to take in food, break
it down into a useful form your
cells can use (nutrients), and
get those nutrients into your
blood so that the circulatory
system can take it to every cell
in your body.
What functions as the fuel for the human body?
● The fuel your body
needs to keep
working is food .
Parts of the Digestive System
1. Mouth
2. Esophagus
3. Stomach
4. Small Intestine
5. Large Intestine
6. Liver (A)
7. Gallbladder (B)
8. Pancreas (C)
What is Digestion?
● Food is too big and complex for your body cells.
It must be changed before your cells can use it.
● Digestion is a process that changes food into a
form your cells can use. (nutrients).
● During digestion food is broken down into very
small materials.
Breaking Food Down
Your body breaks down food two ways:
● Mechanical Digestion – Involves the tearing,
crushing and mashing of food. Example: When you
take a bite and chew it with your teeth or when your muscles of the
stomach contract and relax.
● Chemical Digestion – When chemicals called
enzymes help break down food into nutrients.
What is the path food takes through your body?
1) Mouth – Food is shredded by the teeth and
Mouth
v
mixed with saliva. Saliva breaks down starches
into simple sugars and softens and moistens the
Esophagus
food. The tongue pushes the food, now called
v
bolis, down the esophagus.
Stomach
v
2) Esophagus – The muscles in the
Small Intestine
esophagus push the bolis down into the stomach
v
while its walls, lined with mucus, makes it easier
Large Intestine
for the food to slide down.
v
Rectum/Anus
What is the path food
takes through your body? (Cont.)
3) Stomach – Food is churned and mixed with
Mouth
digestive juices (enzymes and acid) that break protein
v
causing the bolis to becomes a thick liquid, with the
Esophagus
consistency of a milkshake (chyme).
v
4) Small Intestine – Partly digested food moves
Stomach
from the stomach to the small intestine, where it mixes with
v
chemicals from the pancreas and the liver. Digested food
passes into the bloodstream through the villi, which line the Small Intestine
v
small intestine walls, and are transported throughout the
body.
Large Intestine
v
Rectum/Anus
What is the path food takes through your body?
(continue)
5) Large Intestine – Materials that cannot be
absorbed pass into the large intestine. The large
intestine absorbs water and stores waste until it can
be eliminated from the body.
6) Rectum/Anus – solid waste, called feces, is
eliminated from the body through the rectum.
Mouth
v
Esophagus
v
Stomach
v
Small Intestine
v
Large Intestine
v
Rectum/Anus
What is a nutrient?
● Nutrient - Any substance found in food that is
useful for your body.
How do nutrients move from the
small intestine to the body cells?
● The small intestine is lined with fingerlike bumps called villi. Villi
increase the surface area of the small intestine. This helps the
transport of nutrients, because it means there are more places
for nutrients to be absorbed into the blood.
● Villi are full of capillaries. Nutrients move from the villi of the
small intestine into these capillaries through their thin walls.
What system works with the digestive system to
transport nutrients to your body cells?
● The Circulatory System takes the nutrients digested by
the digestive system (and which have passed into the
blood through the thin walls of the villi in the small
intestine) and transports it throughout the body to each
of the body cells.
What does the stomach, liver
and pancreas have in common?
● They each secret chemicals that help break
food down.
What’s the role of the liver?
● The Liver produces bile which breaks down fat.
What’s the role of the gallbladder?
● The Gallbladder stores bile, produced by the
liver, and releases it to the small intestine
when it is needed.
What’s the role of the pancreas?
● The Pancreas produces enzymes that flow into the
small intestine to help neutralize stomach acid.
These enzymes are mixed with food as it enters
the small intestine.
What is Peristalsis?
● Peristalsis is the strong wave-like muscle
contractions in the organs of the digestive
system that occur automatically in order to help
move food along from one part to the next.