1. The Digestive System
7th Grade Life Science

2. Three Major Functions of the Digestive System
Break down ingested food
Put nutrients into the bloodstream for delivery to the cells.... glucose will be used to make ATP energy and amino acids will be used to make proteins.
Remove waste from the body

3. Organs of the Digestive System
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine

4. 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.

5. 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

6. 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 ..

7. 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

8. Can you name these organs?B. C. D. E.
Food never touches the accessory organs!

9. 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

10. 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!

11. 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.

12. The End!
Great National Geographic video
Where will I go?
Let’s Digest Something!