Transcript Jan 4, 2010 AIM: How does the digestive system change food into

Jan 4, 2010
AIM: How does the digestive system
change food into usable nutrients?
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DN: WITHOUT using notes, books, or your
classmates, draw and label the digestive
system. Hand it in!
HW: Finish the Homeostasis handout using p.
471-475.
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Also, read p. 480-481.
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Quiz Friday
Digestive System
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Converts (changes)
food into nutrients
that the body's cells
can use
These nutrients can
be used for chemical
reactions in the body
or build new cells
What are some
nutrients and their
purposes?
Two Types of Digestion
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Mechanical – physical change, large chunks of
food is broken down into smaller pieces. Done
by chewing, stomach churning
Chemical – chemical change, the molecular
bonds of food are changed, breaking them
down into smaller molecules. Done with saliva,
digestive juices and enzymes.
Digestion Begins in the Mouth
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Chewing
Glands make saliva,
that mix with food
Saliva makes food
easier to swallow
Saliva has digestive
enzyme amylase,
which begins starch
breakdown
Swallowing
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Muscles in mouth and
tongue push food down
the esophagus (food
tube)
Epiglottis – flap that
covers the trachea
(windpipe) when
swallowing, to prevent
choking
Down the hatch!
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Peristalsis – involuntary
muscular contractions
that push food down the
digestive system
Think of the digestive
system as one long tube
starting at the mouth,
and ending at the anus
After swallowing, food
travels from the mouth
down the esophagus to
the stomach
Stomach
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Muscular sac
More mechanical
digestion
Chemical digestion:
acids and enzymes
(pepsin, which begins
protein breakdown)
Valves (one way
openings), aka
sphincters, connect
stomach to esophagus
and small intestine
To the small intestine!
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Stomach churns food
into a thick, soupy
mixture called chyme
Peristalsis pushes the
chyme through
stomach to small
intestine
Small Intestine
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The MOST chemical
digestion takes place
here
Several different
enzymes break down
food into its
component nutrients
Enzymes and juices
from other glands
(pancreas, liver) are
sent here
Small intestine – site of absorption
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Villi line the small intestine, maximize nutrient
absorption
Nutrients pass through the villi
Nutrients are absorbed into the bloodstream, are
carried to cells
To the Large Intestine
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Undigested food is
pushed to the large
intestine (aka colon)
Any water, vitamins,
minerals still in food
absorbed
Solid waste (feces)
exit through the anus
Wrap-Up – To Hand In!
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Why can the digestive system be considered
one long tube?
Vomiting is also called “reverse peristalsis”.
Explain why.
Solid waste leaves the digestive system through
the anus of the large intestine. How do you
think liquid waste leaves the body?