Download The Digestive System

The Digestive System
(Ch. 15 Sections 2 and 3)
1. Functions of the digestive system:
a. digestion--breaks down food into usable molecules
b. absorption--absorbs molecules into the blood and carries it to
the body
c. elimination--wastes are eliminated
THE MOUTH:--digestion begins here
2. mechanical digestion:
in the mouth it occurs when biting and chewing
3. chemical digestion:
chemicals in saliva begin breaking down food in the mouth
4. saliva:
fluid in the mouth that begins chemical digestion
***bolus: wet mass of food and saliva
5. enzymes:
proteins that speed up chemical reactions in the body
THE ESOPHAGUS—
6. epiglottis:
flap of tissue that seals off the windpipe (trachea) when swallowing
7. esophagus:
muscular tube connecting the mouth to the stomach
8. peristalsis:
involuntary muscle contractions that keep food moving in one
direction; it occurs in the esophagus, stomach, and intestines
THE STOMACH—
9. stomach:
J-shaped muscular pouch in the abdomen
10. mechanical digestion:
most mechanical digestion occurs in the stomach; muscles contract to
churn the food
11. chemical digestion:
**digestive juice contains the enzyme pepsin
**pepsin works best in an acid environment
**pepsin breaks proteins into short chains of amino acids
**hydrochloric acid is the stomach acid that helps pepsin work
**chyme—soupy mass of food that moves from the stomach to the
small intestine
SMALL INTESTINE—
12. small intestine:
most chemical digestion and absorption take place here
13. liver:
largest organ; produces bile----bile flows from the liver to the
gallbladder (food does not pass through the liver)
14. bile:
substance that breaks up fat particles; this is a mechanical process,
not a chemical process
15. gallbladder:
stores bile; after eating, bile passes from the gallbladder to the small
intestine through a tube (food does not pass through the gallbladder)
16. pancreas:
triangular shaped organ between the stomach and small intestine;
produces enzymes that flow into the small intestine and help break
down starches, proteins, and fats (food does not pass through the
pancreas)
17. villi:
finger-like structures covering the small intestines; villi absorb
nutrients and pass them on to blood vessels
LARGE INTESTINE—
18. large intestine:
contains helpful bacteria; material entering the large intestine
contains water and undigested food----the water is absorbed into the
bloodstream, and remaining material gets ready for elimination
19. rectum:
short tube at the end of the large intestine; waste material is
compressed into solid form
20. anus:
muscular opening at the end of the rectum; waste exits the body here