The document summarizes the key parts and functions of the human digestive system. It describes how food is ingested and passes through the mouth, esophagus, stomach, small intestine, and large intestine. In each section, mechanical and chemical digestion breaks down food into smaller molecules that can be absorbed into the bloodstream. Enzymes and acids produced throughout the digestive system help break down proteins, carbohydrates, and fats. The small intestine contains villi that increase absorption surface area and take in nutrients into the bloodstream. Undigested waste is eliminated from the body through the large intestine and rectum.

1. THE DIGESTIVE
SYSTEM
Chapter 2 Section 2

4. FUNCTIONS
OF THE
DIGESTIVE
SYSTEM
Digestion is the process
that breaks down food
into small molecules so
that they can be absorbed
and moved into the blood,
then on to the cells.

5. FOOD IS
PROCESSED IN
YOUR BODY IN
4 STAGES
ingestion
digestion
absorption
elimination

6. MECHANICAL
DIGESTION
Takes place when food is
chewed, mixed, and
churned. This mainly
occurs in the mouth and
stomach.

7. CHEMICAL
DIGESTION
occurs when chemical
reactions occur that break
down large molecules of
food into smaller ones.

8. ENZYMES IN
DIGESTION
Enzymes help you
digest carbohydrates,
fats and proteins.
Amylase is an enzyme
produced in a gland
near the mouth.
Amylase helps speed
up the breakdown of
complex carbs, such as
starch, into simpler
carbs - sugar.

9. ENZYMES IN
DIGESTION
In your stomach, the
enzyme pepsin helps
in the breakdown of
complex proteins into
less complex proteins.
In your small intestine,
many other
enzymes continue to
speed up the
breakdown of proteins
into amino acids.

10. ENZYMES IN
DIGESTION
The pancreas, an organ
on the back outside of the
stomach, releases
several enzymes
through a tube into the
small intestine.
They breakdown starches
that started to be broken
down in the mouth. The
starches are broken down
into glucose to be used by
cells.
Other enzymes from the
pancreas are involved in
the breakdown of fatty
acids and proteins.

11. ENZYMES

13. The human digestive system is like a long tube with
specialized sections. If it is stretched out, it would be
_________ meters long.
6 to 9 meters!!!!!!!
Absolutely mind-boggling!

14. DIGESTIVE SYSTEM
HAS 2 PARTS
the digestive tract the accessory organs
mouth
esophagus
stomach
small intestine
large intestine
rectum
anus
tongue
teeth
salivary glands
liver
gallbladder
pancreas
food passes through food does not
pass through

15. MOUTH
•Mechanical and chemical digestion begins in the mouth.
•Mechanical digestion - when you chew with your teeth
and mix with your tongue.
•Chemical digestion - watery substances called saliva is
added to your mouth. Saliva is produced by 3 sets of glands
near your mouth.
•Saliva - mostly water, but also contains mucus and an
enzyme that helps in the breakdown of starch into sugar.

16. MOUTH
•Food mixed with saliva becomes a soft mass and is moved
to the back of your mouth by your tongue.
•It is swallowed and passes into your esophagus.
•Ingestion is now complete.

18. ESOPHAGUS
•Food that passes from the mouth into the esophagus, first
passes the epiglottis.
•Epiglottis - structure that automatically covers the
opening to the wind pipe to prevent food from entering the
lungs and causing you to choke.
•Esophagus - muscular tube about 25 cm long. It takes
4-10 seconds for food to travel through it.

20. ESOPHAGUS
•No digestion takes place in the esophagus, but there are
mucus glands in the wall to keep the food moist.
•The walls are made of smooth muscles, which move the
food down to the stomach with a squeezing motion called
peristalsis.

22. STOMACH
•Stomach - muscular bag, that when empty is sausage
shaped with folds on the inside.
•As food enters, the stomach expands and the folds smooth
out.
•Mechanical and chemical digestion take place here.
•Mechanical - food is mixed by peristalsis
•Chemical - food is mixed with enzymes and strong digestive
solutions, like hydrochloric acid.

24. STOMACH
•Specialized cells in the walls of the stomach release about 2
liters of HCl solution each day.
•WOW!!
•The acidic solution works with the enzyme pepsin to digest
protein. It also destroys bacteria that are present in the food.
•The stomach also produces mucus, making the food
slippery and protects the stomach from the strong, digestive
solutions.

25. STOMACH
•Food moves out of the stomach after 2-4 hours and is
changed into a thin, water liquid called chyme.
•Little by little chyme leaves the stomach and moves to the
small intestine.

28. SMALL INTESTINE
•The small intestine is small in diameter, but is 4-7 meters longs!
•Food from the stomach enters the first section of the small
intestine called the duodenum. Most digestion takes place here.
•A greenish fluid, bile, is produced in the liver and stored in the
gall bladder.
•The acid from the stomach makes large fat particles float to the
top of the bile.
•Bile breaks up the large fat particles, similar to the way detergent
breaks up grease.

31. SMALL INTESTINE
•Chemical digestion of carbohydrates, proteins, and fats
occurs when a digestive solution from the pancreas is
mixed in.
•The solution contains bicarbonate ions to neutralize the
stomach acid and enzymes to continue the breakdown.
•Your pancreas also makes insulin, a hormone that allows
glucose to pass from the blood stream into your cells.

33. SMALL INTESTINE
•Absorption of food’s nutrients takes place in the small
intestine.
•The wall of the small intestine has many ridges and folds
that are covered with fingerlike projections called villi.
•Villi increase the surface area so that the nutrients in the
chyme have more places to be absorbed.
•By how much do villi increase the surface area of the small
intestine?

34. IF YOU WERE TO STRETCH OUT THE
VILLI OF THE SMALL INTESTINE
THEY WOULD COVER......
...a tennis court!!!!

39. SMALL INTESTINE
•Peristalsis continues to move and mix the chyme.
•Nutrients move into the blood vessels within the villi.
•The blood transports the nutrients to all cells of your body.
•Peristalsis continues to force the remaining undigested and
unabsorbed materials slowly into the large intestine.

40. LARGE INTESTINE

41. LARGE INTESTINE
•When the chyme enters the large intestine it is still thin and
watery.
•The main job of the large intestine is to absorb water
from the undigested mass.
•This keeps large amounts of water in your body and
maintains homeostasis.
•Peristalsis slows down in the large intestine.
•The chyme might stay there for as long as 3 days.

42. LARGE INTESTINE
•After the excess water is absorbed the undigested material
become more solid.
•Muscles in the rectum (the last section of the large
intestine) and the anus control the release of semisolid
wastes from the body in the form of feces.

43. BACTERIA ARE
IMPORTANT
Many types of bacteria are in your body.
They live in many of the organs in your digestive tract,
including your mouth and large intestine, where both your
body and the bacteria are benefitted.
Bacteria in your large intestine feed on undigested material
like cellulose. The bacteria make vitamins you need- vitamin
K and 2 vitamin B’s.

44. BACTERIA ARE
IMPORTANT
Vitamin K is needed is needed for blood clotting. The
Vitamin B’s are needed for your nervous system for other
body functions.
The breakdown of intestinal materials by bacteria produces
gas.