Transcript October 3, 2011 Warm Up

October 3, 2011
Warm Up
1. Pick up this weeks homework
packet from metal basket on
table by door.
2. Collect Journal
3. Work on Homework Packet
(if I don’t see people working on it,
I will make it due first thing
tomorrow)
What is digestion?
• Class Discussion:
What is the digestive
The process by which your body breaks down food
system?
into small nutrient molecules is called digestion.
Digestion of food involves both physical and
chemical changes.
• Physical changes involve the
physical tearing, grinding,
crushing, and churning of
pieces of food. These
processes increase surface
area, which helps speed up the
chemical changes of digestion.
• During chemical changes,
chemicals break foods into
their building blocks.
The organs of the digestive system have
three main functions: digestion,
absorption, and elimination.
What changes occur in the mouth and
Food enters your body through stomach?
your mouth, where physical and chemical
changes begin.
• Your teeth cut, tear, crush, and grind the food
into small pieces. This is a physical change.
• Saliva in your mouth brings about two physical
changes. Saliva moistens food, making it easier
to swallow. It also dissolves some foods, such
as salt.
• Saliva also brings about a chemical change. An
enzyme in saliva begins the breakdown of
starch into sugars. An enzyme is a protein(contd.)
that
speeds up chemical reactions in your body.
When you swallow, food enters the esophagus. Peristalsis, waves of
involuntary muscle contractions, push food toward the stomach. There, more
physical and chemical changes occur.
• Physical Changes Layers of smooth
muscle in the stomach wall contract and
produce a churning motion that mixes
food with fluids in the stomach. Mucus in
the fluids keeps the food moist and
protects the stomach lining from other
chemicals.
• Chemical Changes Gastric fluids also
mix with the food. These fluids contain the
enzyme pepsin, which breaks down
proteins into short chains of amino acids.
Hydrochloric acid provides the acid
environment in which pepsin works best. It
also helps kill many bacteria that you
swallow with your food.
1. Summarize What is the result of the chemical changes that occur in the mouth and stomach?
What changes occur in the
small intestine?
• Most of the chemical changes of digestion
take place in the small intestine.
• Starches and proteins that reach the small
intestine are partly broken down by the
time they reach the small intestine. Lipids
are not.
• Substances produced by the liver,
pancreas, and lining of the small intestine
help to complete the chemical changes
that turn carbohydrates, proteins, and(contd.)
lipids into small molecules.
2. Infer At 6−7 meters in length, the small intestine makes up two-thirds of the length of the digestive
system. Its diameter is 2−3 cm. From this, infer what gives the small intestine its name.
• Glands in the small intestine release
enzymes that help break down
peptides into individual amino acids.
Other glands produce enzymes that
continue the digestion of complex
sugars, producing the simple sugars
the body uses for energy.
• The liver produces bile, which is
stored in the gallbladder and released
into the small intestine through a duct.
There, bile physically breaks up large
lipid particles into smaller droplets.
• Enzymes produced by the pancreas
act on the droplets and chemically
change them into smaller molecules.
The pancreas also produces enzymes
that help break down carbohydrates
and proteins.
• After these chemical changes occur, the
small nutrient molecules are absorbed
through the surface of the small intestine
into the blood. Villi, tiny finger-shaped
structures, cover the wall of the intestine
and increase its surface area. This allows
more nutrients to be absorbed.
What changes occur in the large intestine?
• By the time material reaches the end of the
small intestine, most nutrients have been
absorbed.
• The water and undigested food that remain
move into the large intestine. There, most of
the water is absorbed into the bloodstream. The
material that is left is readied for elimination
from the body through the rectum.
• As wastes move through the 1.5-meter-long
large intestine, bacteria feed on the material.
These helpful bacteria make certain vitamins,
including vitamin K.
3. Restate What physical changes occur as matter moves through the large intestine?
•Now Let’s Test this
“Digestive System”
• What are some ways a
cracker can be broken down
by the body in order for its
nutrition to be absorbed into
the body?
• Brainstorm ideas on sheet of notebook paper.
What body system has
the function of breaking
down food for
absorption into the
blood?
Cracker Lab
• 1. Each student takes 1/4 saltine cracker and
places in in the tongue in the mouth.
• 2. Students record their observations after 30
seconds.
• 3. Each student takes 1/2 cracker and chews
then records their observations after 30
seconds.
• After powerpoint, students classify which
activity provided evidence for physical and
chemical change.
Physical: teeth grind food into smaller pieces
Chemical: Saliva breaks down food into mush
• 5. After powerpoint, students then swallow the
cracker and records observations after 30
seconds and classified that evidence of
digestion in the esophagus
• After powerpoint notes, students classify
the type of changes in the stomach, small
intestine and large intestine.
Digestive system
process where
food is broken
down through
chewing, mixing
and churning.