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Lesson 6
Digestive System
AIM: How does the digestive system work
to maintain a stable and healthy body?
Do Now:
What are you doing?
What is the Digestive
System?
Digestion – the process that breaks
down food into forms that the body
can use.
Digestive system- organs that break
down food into molecules.
Food provides proteins and
nutrients the body needs.
3 Functions of the Digestive
System
1. It breaks down food into molecules the
body uses.
2. The molecules are absorbed into the
blood stream and carried through to the
body.
3. Wastes are eliminated from the body.
Parts of the Digestive system
Esophagus
Stomach
Small Intestine
Large Intestine
Liver
Gall Bladder
Pancreas
2 types of Digestion
There are two ways that digestion takes
place.
1. Mechanical Digestion
2. Chemical Digestion
Together these two processes change food
to atoms and molecules.
Mechanical Digestion
Is a physical change that
results in breaking up
food into smaller pieces.
Done by the mouth and
teeth.
 Chewing
 Mixing
 Biting
 Tearing
Chemical Digestion
 Chemicals break
down large
molecules into
smaller parts.
 Is a chemical
change that
breaks down your
food.
Ex: saliva, acid in
the stomach and
small intestine.
Video: 5:35-8
Enzyme- a protein that
produces chemical
reactions
Check For Understanding
Which statement about digestion is true?
A.Saliva digests food mechanically; teeth digest it
chemically.
B.Mechanical digestion and chemical digestion
occur in the large intestine.
C.Enzymes digest food chemically; teeth digest
food mechanically.
D.Chemical digestion mashes up food; mechanical
digestion breaks it up with enzymes.
Do Now
 AIM: What is the difference between
mechanical and chemical digestion?
 Write heading and AIM in notebook.
 As soon as you are completely quiet, I
will distribute something….
Digestion in the mouth
 1. Put half the cracker in your mouth
and chew.
In your notebooks, record what it tastes
like. Sweet? Plain? Hard? Soft? Salty?
(bullets are fine.)
 2. When I say to begin, you will put the
second half of the cracker in your mouth, but
you WILL NOT chew it.
 You will keep it in your mouth for 1.5 minutes.
When I give you the signal, think about the
following questions:
 A. What does it feel like at first?
 B: after 1 minute?
 C. After 1.5 minutes?
 D. When you chew it?
Human Digestion
 http://www.discovery.com/tv-shows/othershows/videos/assignment-discovery-shorts-06-07-0708-human-digestion.htm
The Steps of Digestion
1. Mouth
Where food enters the
digestive system.
 In the mouth food is
chewed up
 Teeth bite the food and
chew it before it moves on
to the tongue
 The tongue moves the
food around mixing it with
saliva.
Saliva
Is a secretion that contains an
enzyme important for breaking
down food.
Within the mouth both
mechanical and chemical
digestion occur.
2. Esophagus
 A muscular tube that
connects the throat to the
stomach
 Is about 10 inches long
 It takes about 4-10 seconds
for food to move down your
esophagus.
 No digestion takes place
here.
Esophagus continued
 The walls of the
esophagus are layered
with muscles that squeeze
and push food along in
process called “Peristalsis”
 Food travels through the
esophagus towards the
stomach.
3. Stomach
 the stomach is a
muscular bag like
organ that can shrink
and stretch.
Food is temporarily
stored here
Stomach continued
 Both chemical
and mechanical
digestion
 Mechanical:
The muscles of
the stomach
contract mixing
all of the food
inside it
together
Chemical: food is
mixed with enzymes
and strong digestive
juices like hydrochloric
acid to break it down
Stomach continued
 Stomach also produces
mucus which protects the
wall from the strong
digestive juices .
 Food moves through your
stomach in 2-4 hours.
 Turns partially digested food
into a watery substanceChyme
AIM: How does the digestive system get
nutrients to our cells? (How does a turkey
sandwich give us energy?)
Do Now: Write heading and
AIM. In notebooks, write down
some possible answers to the
AIM question.
4. Small Intestine
About 22 feet long!!!
 Finishes chemical
digestion of food.
 Absorbs nutrients and
sends them to the
bloodstream
 Villi – finger-like
structures covering inner
wall, allow for absorption
of nutrients
Small Intestine: Part 1: Duodenum
 First part of the small
intestine which is
connected to the
stomach.
 Most digestion takes
place here
 Bile from the liver is
added to help break
down particles.
5. Large Intestine
About 5 Feet long
• Absorbs what the small
intestine does not
absorb
• Takes undigested food
and turns it into waste.
• LI keeps water in your
body to maintain
homeostasis.
• Video 8:50-11
You can lose a large part
of your large intestine and
still survive
Check For Understanding
Which is a function of the large intestine?
A.It absorbs nutrients from food and puts them
into the bloodstream
B.It takes nutrients to all the cells of your body
C.It breaks down food chemically
D.It absorbs extra liquid from food your body
could not digest
Liver
• Affects digestion by
producing bile
• Bile- Helps digest fat
 Processes nutrients in the
blood, filters out toxins
and waste.
 Is often called the body’s
energy factory.
 You cannot live without a
liver, although you can
live with a part of one.
 Drinking alcohol damages
the liver.
Gall Bladder
 Stores bile from the
liver.
 Delivers bile when
food is digested.
 Fatty diets can
cause gallstones.
 You can live without
a gallbladder.
Pancreas
 Produces digestive
juices for further
break down food.
 Regulates blood
sugar by producing
insulin.
(homeostasis)**
 If it does not work
you get diabetes.
Bacteria
 Many types of bacteria live
in your body and organs
 Some are good for you
 Bacteria in the digestive
system make vitamins you
need.-Vitamin K and two B
vitamins.
 Vitamin K- blood clotting
 Vitamin B-helps nervous
system.