1. The Digestive System (ch. 35)
Digestion (35.1)
I. Functions of Digestive System
A. Breaks food into smaller, simpler molecules cells can use!
1. Mechanically
2. chemically
B. Absorbs these simpler molecules and distributes them to cells via blood
C. Eliminates undigested wastes
Digestion Video:
DIGESTIVE ORGANS

2. II. The functions of each organ
A. Mouth
1. mechanical breakdown (chewing)
2. chemical digestion of starches by salivary amylase. (makes mono- and di- saccharides)
3. Tongue shapes food into ball and you swallow using pharynx.
epiglottis (flap of cartilage) prevents food from going down the wrong pipe!!

3. B. esophagus—muscular tube that connects mouth and stomach
1. peristalsis—involuntary smooth muscle contractions that move food down esophagus.
C. Stomach
1. muscular churning (mechanical digestion)
2. chemical digestion—gastric juice containing pepsin and hydrochloric acid (HCl)
a. pepsin (an enzyme)—breaks down proteins
b. HCl—helps pepsin work by making stomach acidic (pH 2).
c. mucus layer keeps stomach from digesting itself.

4. D. Small Intestine (about 6 m long tube!!)
1. finishes off the breakdown and digestion of food particles (takes 3-5 hrs.)
2. other organs secrete enzymes and chemicals into small intestine
a. *liver—secretes bile (to break down fats)
b. *gallbladder-- stores bile and secretes it into small intestine.
c. *pancreas—secretes other digestive enzymes that break down carbs, proteins and fats. Also pancreatic juices neutralize the acid coming from stomach.
*= food does not pass through these organs—they secrete stuff into the intestine.

5. 3. digested food is absorbed in small intestine
Small intestine continued…
3. digested food is absorbed in small intestine
a. villi—projections on surface of small intestine that absorb digested food
increase surface area of small intestine.
This is where nutrients pass into blood.

6. Villi and microvilli

7. 2. rectum—holds feces until expulsion
E. Large intestine
1. absorbs water and certain vitamins (K and B vitamins made by anaerobic bacteria living in intestine)
2. rectum—holds feces until expulsion
3. Anus – where feces are eliminated.
Hirschsprung's disease and Jesus Alberto
DIGESTIVE ORGANS
Digestion overview animation

8. Magic School Bus Evaluation
How are each of the following organs portrayed in the Magic School Bus:
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Evaluate how accurately the digestive system is portrayed.

9. 35.2 Nutrition
I. Six Basic Vital Nutrients
A. Carbs
1. sugars, starches, cellulose* (fiber) *indigestible but important for waste elimination
2. energy source, glycogen stored in liver till needed.

10. B. fats
1. energy, structural building blocks (plasma membrane etc), insulation, organ cushioning, hormone synthesis
2. broken down into fatty acids and glycerol in digestive system. (fatty acids may be converted to glycogen or stored as fats throughout body in adipose tissue)

11. Saturated vs. unsaturated

12. C. Proteins
1. enzymes, antibodies, hormones, structural proteins like muscle, clotting factors etc.
2. breakdown into amino acids (used to form necessary proteins)
3. liver can convert a.a’s to glucose or fats in emergencies.
4. 8 essential amino acids—can’t be made by body, must be consumed
*note: All 20 amino acids are necessary for protein synthesis

13. 2. Co-enzymes—fit onto enzymes to help them function
D. Minerals
1. inorganic substances that serve as building material or take part in chemical reactions in body.
E. Vitamins
1. organic nutrients needed in small amounts to maintain growth and metabolism.
2. Co-enzymes—fit onto enzymes to help them function
3. fat- soluble—can be stored in liver (excess= toxic)
4. water-soluble—can’t be stored.
F. Water
1. most abundant body substance
2. needed for chemical reactions, digestion, as a solvent, to maintain body temp. etc.
Zinc
Magnesium
Vitamin D

14. II. Calories and Metabolism
A. Calories are units of heat that measure energy content of food.
B. 1 Calorie= 1 kilocalorie= 1000 calories
C. a calorie is the amount of heat required to raise the temp of 1 ml of water by 1 degree Celsius
D. Metabolic rate = the rate at which a person burns energy—varies for different people.