Transcript The Digestive System

The Digestive System
7th Grade Life Science
Major Functions of the Digestive System
• Break down ingested food
• Put nutrients into the bloodstream
• Remove waste from the body
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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html
Organs of the Digestive System
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Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Mouth
• Digestion begins here!
• Teeth and tongue are used in mechanical
digestion to crush the food into smaller pieces
• Saliva and enzymes (Amylase) begin chemical
digestion
• to break down starches to sugars.
Esophagus
• Muscular tube connects mouth (pharynx) to stomach
• Moves food downward by peristalsis, or
muscular contractions
• Epiglottis seals off windpipe during swallowing to
prevent choking
• What are sphincters? Narrow sections of the
digestive tract that keep food moving the right
direction
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www.dnatube.com/video/29949/All-About-Peristalsis
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http://www.youtube.com/watch?v=Ujr0UAbyPS4
Stomach -Lots of Churning!
(mechanical)
• The mechanical digestion of proteins begins here.
• Muscular pouch that expands to hold your food
• Hydrochloric acid (HCl) and the enzyme pepsin combine to form
gastric juice A gummy coating of mucus protects the stomach
lining from the strong chemicals (prevents ulcers)
• Chyme, a thick liquid containing partially digested food, is
produced here
• Most bacteria are killed by the stomach acid but ..
http://foodsafe.ucdavis.edu/html/audio/stomachache_tonight.html
Small Intestine Most chemical digestion here!
• Longest portion of the digestive tract!
• First section or the duodenum - enzymes from
accessory organs enter to aid digestion
• Accessory Organs:
• Liver-over 200 jobs... breaks down toxins,
stores nutrients, and produces bile
• Gall bladder (tiny sac below liver) stores bile that goes to the
duodenum to mechanically break down fats
• Pancreas sends pancreatic juice to the duodenum to
neutralize stomach acid and complete the digestion of all
foods http://www.zerobio.com/secretin_flash.htm
Can you name the accessory
organs?
A.
B.
C.
D.
E.
Food never touches these!
• Inner surface is covered in villi and microvilli, millions
of tiny finger-like projections that increase the surface
area to allow absorption of nutrients from the chyme
into the blood
Small Intestine shape…
 Which of these is the correct form of the small intestine?
A! Why does the small intestine have this shape?
If shape B occurs, with no villi to slow the food, it would pass too
quickly through the system to be absorbed.
Starvation!
Large Intestine - Colon
• No digestion occurs here
• Water is absorbed from remaining food
• Bacteria feed on material passing through and
produce vitamins vital to our health
• Waste material, feces, is prepared for elimination
from the body. It is stored in the rectum until it
leaves the body through the anus.
The End!
Where will I go?
 www.youtube.com/watch?v=OYWVbt6t2mw
Let’s Digest Something!
http://kitses.com/animation/swfs/digestion.swf