1. The Digestive System
Presented By:
Mrs. Nelson

2. Nutrition
 Nutrition is the study of how food affects
the function of living organisms.
 Food contains nutrients.
 Nutrients provide the energy and materials
organisms need.
 If organism’s cells are not provided with
nutrients, the cells will not function
properly.
 Poor diet = poor cells

3. Six Categories of Nutrients
Energy Suppliers
 Carbohydrates
 Lipids
 Proteins
Non-Energy Suppliers
 Water
 Vitamins
 Minerals

4. Carbohydrates
 Glucose is main source of carbohydrates
for animals.
 Glucose is easily converted to ATP.
 Glucose is found in fruits, vegetables,
grains, and dairy foods.
 Many foods contain cellulose also known
as “fiber.” Important for helping push food
through the digestive tract.
 Energy from food is measured in
“calories.”

5. Lipids
 Provide twice as much energy as carbohydrates.
 Important for…
1) Making cell membranes
2) Hormone production
3) Myelin production
4) Protect organs and insulate body
 Take long time to digest.
 Too much fat in diet= excess energy = fat
deposits.
 Saturated fats (solid, contain single bonds)
contain LDL cholesterol and build up on arteries.

6. Proteins
 Proteins made of amino acids.
 20 different amino acids.
 Body can make 12/20 amino acids.
 The other eight must come from food are
called “essential amino acids.”
 Proteins are materials needed for…
1) growth and repair.
2) skin and muscles.
3) regulatory (enzymes- insulin) and transport
functions (hemoglobin– RBC).

7. Water
 Most important nutrient.
 Lubricates areas of body (blood, lymph,
plasma, etc.)
 Coolant for body.
 Solvent for digestion.
 Provides fluid environment for cells.
 Body needs intake 1L of water a day.

8. Minerals
 Inorganic (not made by living things).
 Plants absorb minerals.
 Animals eat plants to get minerals.
 Minerals are only needed in trace amounts
by the body.
 Iron (hemoglobin RBC)
 Calcium (bones and teeth)
 Sodium/Potassium (nerve and muscle
function)
 Magnesium/Zinc/Iodine

9. Vitamins
 Organic (made by living things).
 Help regulate body processes.
 Most obtained from food.
 Vitamin K- made by bacteria in digestive tract.
 Vitamin D- synthesized by skin cells when
exposed to sunlight.
 2 types vitamins…
1) Fat soluble- can be stored in fatty
tissues for future use (A, D, E, K)
2) Water soluble- dissolve in water and can
not be stored by body (C, B)

10. Importance of Various Vitamins
 A, C, D, E, K, Folic Acid, B12
Helps RBC mature

11. The Digestive System
 System is responsible for breaking down food
so that nutrients can be absorbed by the
bloodstream.
 The “alimentary canal” is the pathway which
food travels while it is digested.

12. The Alimentary Canal
 Mouth
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Rectum
* The liver, pancreas, and gallbladder are parts of
the digestive system but are not parts of the
alimentary canal.

14. The Mouth
 Chemical digestion –saliva contains
enzyme amylase that digests
carbohydrates (starches)
 Mechanical digestion- chewing

15. Esophagus
 Tube from back throat
to stomach.
 Trachea (lungs) and
esophagus are next to
each other.
 Epiglottis prevents food
from going down the
wrong tube.
 Peristalsis- muscular
contractions pushes
food down esophagus.

16. Stomach
 Chemical/mechanical
digestion.
 Hydrochloric acid and
pepsin (enzyme) break
down proteins to
amino acids.
 Stomach lining contains
mucus.
 Mucus protects stomach
from acid (ulcers).
 Sphincter muscles (cardiac
and pyloric) control what
enters and leaves the
stomach (heartburn).

17. Small Intestine
 20 ft.
 Remaining carbohydrates
and proteins are broken
down.
 All lipids are digested here.
 Connected to liver and
pancreas.

18. Liver and Pancreas
LIVER JOBS
 Makes and secretes
bile (needed digest
lipids).
 Bile is stored in the
gall bladder.
 Detoxifies drugs and
alcohol.
PANCREAS JOBS
 Regulates blood
sugar.
 Secretes digestive
enzymes into small
intestine.
 Neutralizes stomach
acid as it enters the
small intestine
(bicarbonate).

19. Small Intestine (cont.)
 After all nutrients are
digested, they are
absorbed. This is the
major job of this
organ.
 S.I. contains lots of
capillaries.
 Mesentary.

20. Large Intestine
 All proteins,
carbohydrates, and
lipids have been
removed from food by
the time it gets here.
 Water is absorbed
(diarrhea).
 Vitamins are absorbed.
 Feces is undigested
food passes out rectum
and anus.