Introduction
• The digestive
system is used for
breaking down food
into nutrients which
then pass into the
circulatory system
and are taken to
where they are
needed in the body.
Components
•
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•
•
•
Esophagus
Stomach
Small Intestine
Large Intestine
Gall bladder
Liver
Pancreas
• There are four
stages to food
processing:
1.Ingestion: taking in
food
2.Digestion: breaking
down food into
nutrients
3.Absorption: taking in
nutrients by cells
4.Egestion: removing
any leftover wastes
I. The Digestive Process Begins
1. Digestion:
The process by which
your body breaks down
food into small nutrient
molecules.
(mechanical and chemical)
2. Absorption:
The process by which nutrient molecules
pass through the wall of your digestive
system into your blood.
3. Elimination:
Materials that
are not absorbed
are eliminated
from the body
as waste (ie.
Fiber)
Diagram of Digestive System
Mouth
• Chemical and
mechanical
digestion.
• Food is chewed
(masticated)
mechanically.
• A bolus (lump) is
formed with saliva
and the tongue.
B. Mouth
1. Saliva: Fluid released when your mouth
waters and plays an important part in both
mechanical and chemical digestion.
Types of Digestion
2. Mechanical Digestion- Teeth begin digestion
by cutting, tearing, and grinding food
mouth
break up food
digest starch
kill germs
moisten food
C. Esophagus- Total Time 10 seconds.
1.
1. Epiglottis:
Flap of tissue that seals off your windpipe
preventing food from entering.
2. Esophagus:
Food enters a muscular tube that connects the
mouth to the stomach.
3. Mucus:
Thick, slippery substance that lines the
esophagus in order to make food easier to
swallow and move along
• You have a trap door called the
epiglottis to cover your
windpipe when you swallow.
Peristalsis
• series of involuntary
wave-like muscle
contractions which
move food along the
digestive tract
Stomach
• Food is temporarily
stored here.
• Gastric juices are
secreted.
• Has layers of
muscle that line the
inside.
• Mechanically and
chemically breaks
down food.
1. Mechanical Digestion: Three strong layers of smooth
muscle contract to produce a churning motion.
(similar to a washing machine)
2. Chemical Digestion: Churning food makes contact
with digestive juices.
a. Enzyme Pepsin- Works best in an acid environment.
b. Hydrochloric Acid (HCl).-Kills many bacteria that you
swallow with food, mucus protects stomach lining from
this acid.
c. Food remains in the stomach until the entire solid has
been broken down.
• Your stomach mashes your
food the way a baker kneads
dough for bread.
• Your stomach stretches
when you eat like a balloon
being filled with air
mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
sphincter
sphincter
Small Intestine
• Most chemical
digestion takes place
here.
• Simple sugars and
proteins are absorbed
into the inner lining.
• Fatty acids and
glycerol go to lymphatic
system.
• Lined with villi, which
increase surface area for
absorption, one cell
thick.
3. Absorption in the Small Intestine
a. Villi:
Fingerlike structures increase the
surface area of the small intestines
and allow nutrient molecules to pass
into the blood
Small Intestine
• Tube that is 20 feet long.
• Continues to digest food
• Food stays in your small intestine for
4 to 8 hours
Large Intestine
• Solid materials pass
through the large
intestine.
• These are undigestible
solids (fibers).
• Water is absorbed.
• Vitamins K and B are
reabsorbed with the
water.
• Rectum- solid wastes
exit the body.
Large intestines
(colon)
• Function
– re-absorb water
• use ~9 liters of water every
day in digestive juices
• > 90% of water reabsorbed
– not enough water absorbed
» diarrhea
– too much water absorbed
» constipation
B. The Large Intestine
-The last section of the digestive system that
contain bacteria that feed on material and make
vitamins (1.5 meters long)
-The role is absorb water into the bloodstream
and get remaining material ready for
elimination.
Large Intestine
• Tube that is 5 feet long
• Gets waste from small intestine
• Waste stays for 10 to 12 hours
Rectum
• Last section of colon
(large intestines)
– eliminate feces
• undigested materials
– extracellular waste
» mainly cellulose
from plants
» roughage or fiber
– masses of bacteria
Accessory Organs
• Pancreas
• Gall Bladder
• Spleen
Pancreas
• An organ which secretes both digestive
enzymes (exocrine) and hormones (endocrine)
• ** Pancreatic juice digests all major nutrient
types.
• Nearly all digestion occurs in the small intestine
& all digestion is completed in the SI.
Gall bladder
• Pouch structure located near the liver
which concentrates and stores bile
• Bile duct – a long tube that carries BILE.
The top half of the common bile duct is
associated with the liver, while the bottom
half of the common bile duct is associated
with the pancreas, through which it passes
on its way to the intestine.
BILE
• Bile emulsifies lipids (physically breaks
apart FATS)
• Bile is a bitter, greenish-yellow alkaline
fluid, stored in the gallbladder between
meals and upon eating is discharged into
the duodenum where it aids the process of
digestion.
mouth
break up food
digest starch
kill germs
moisten food
liver
produces bile
- stored in gall bladder
break up fats
pancreas
produces enzymes to
digest proteins & starch
stomach
kills germs
break up food
digest proteins
store food
Healthy Habits
• Eat foods that
are high in fiber
like fruits and
vegetables
• Drink plenty of water
• Chew your food completely
before you swallow
Avoid foods high in fat
Interesting Facts
• Food is in your digestive system
for about 24 hours