1. The Digestive System
Chapter 22-3

2. Science Words/Objectives
Digestion
Mechanical digestion
Chemical digestion
Saliva
Peristalsis
Chyme
Villi

3. Objectives Distinguish between mechanical and chemical digestion
Mane the organs of the digestive system and describe what takes place in each
Explain how homeostasis is maintained in digestion

4. Processing food
Digestion- the process that breaks down food into small molecules so they can move into the blood.
Introduction to
Digestion

5. Digestive system Mouth Esophagus Stomach Small intestine
Large intestine
Rectum
anus
Does not pass thru the liver, pancreas, gallbladder- they produce or store enzymes and chemicals that help break down food as it passes through the digestive tract
Parts of digestive
system,

6. Enzymes
Are molecules that speed up the rate of chemical reactions in your body.
Enzymes in the mouth, stomach, small intestine,.
Breaks down proteins and fats

7. Where and How digestion occurs
Mechanical digestion-takes place when food is chewed and mixed in the mouth and churned in the stomach.
Chemical digestion-breaks down large molecules to small molecules. Mouth, stomach and small intestine
Forms of Digestion

8. Mouth Mechanical digestion starts with your teeth.
Chemical digestion starts with your saliva.
Saliva-produced by 3 glands, is water, mucus, and salivary amylase(enzyme)
Moved by tongue- swallowed into esophagus.
The Mouth

9. Esophagus Muscular tube 25 cm long, 4-10 seconds to go through it
No digestion takes place
Smooth muscles move food by squeezing.
Peristalsis- waves or contractions
The Esophagus

10. Stomach Is a muscular Bag.
As food enters it expands and the folds smooth out
Mechanical and chemical digestion
Changes into a thin watery liquid called chyme, which goes into the small intestine
The Stomach

11. Small Intestine 4-7 meters in length
Enters the duodenum where most of all digestion takes place.
Liver produces bile to help break down food
Pancreas produces enzymes to break down fats and proteins
Gall Bladder and
Pancreas
Small Intestine

12. Small intestine
The small intestine has ridges and folds, the folds are covered with tiny fingerlike projections called villi.
Villi make the surface of the intestine greater so that there are more places for food to be absorbed.

13. Large Intestine
Main job is to absorb liquid from chyme- undigested materials become more solid.
Large intestine

14. The Role of Bacteria
Bacteria feed on cellulose and produce several vitamins that you need

15. Digestion and Nutrients

16. Homeostasis
The regulation of steady, life maintaining conditions inside an organism or cell, despite changes in its environment.
Water is removed and returned to the body

17. References
Glencoe Life Science
UnitedStreaming.com
Adam.com