Digestive System

Digestive System

I. DIGESTION – THE PROCESS THAT BREAKS FOOD INTO SMALL MOLECULES SO THEY CAN BE ABSORBED OR TAKEN INTO BODY CELLS.

A. Mechanical digestion

1. Food chewed and mixed in mouth.

2. Food churned in stomach.

3. Food acted on by bile.

Digestive System

B. CHEMICAL DIGESTIONS

1. Breaks down large molecules to smaller.

2. In mouth , stomach, small intestines3. Enzymesa. Proteins vital for chemical

digestionb. Enters a reaction and helps

to join or break up into substances

c. Are not changed themselves

d. Can speed up reactions

Digestive System

II. DIGESTION IN MOUTH

A. Mechanical digestion by tongue and teeth

B. Chemical digestion 1. Salivaa. Produced by the 3 sets of

salivary glandsb. Mostly water, but also

contains mucus and enzymes (amylase)

c. Amylase starts breakdown of starch to sugar.

DIAGRAM OF THE MOUTH

Digestive System

C. ESOPHAGUS

1. Muscular tube2. 25 cm. long3. No digestion4. Peristalsis- waves of

contractions that move food

a. Takes about 4 to 8 seconds

b. Peristalsis found throughout digestive systems

ESOPHAGUS DIAGRAM

Digestive System

III. DIGESTION IN THE STOMACH

A. A muscular bag with folds on the inside

B. Mechanical digestion done by walls of stomach and peristalsis.

DIAGRAM OF THE STOMACH

Real view

Digestive System

C. CHEMICAL DIGESTION

1. Hydrochloric acid2. Enzymes work on protein3. Mucusa. Lubricates food, making

it slick b. Protects stomach lining

from strong digestive juices

D. Food in stomach about 4 hours

E. Food changed to chyme - thin , watery liquid

INSIDE THE STOMACH

Digestive System

IV. DIGESTION IN THE SMALL INTESTINE

A. Small in diameter, but about 6-7 M long

B. - first part of the duodenum small intestine

1. Major part of all digestion

2. Receive digestive juices from outside the digestive tract

a. Bile1. From the liver2. Greenish color

SMALL INTESTINES DIAGRAM

Digestive System

SMALL INTESTINES CONTINUE

3. Store in small sac : the gall bladder

4. Breaks fat molecules into smaller pieces

(like detergent acts on grease)

b. Pancreas1. Produces insulin - helps

body use sugar and other carbohydrates

2. Produces enzymes that break down carbohydrates, fats, proteins still further

DIAGRAM OF GALLBLADDER

Digestive System

C. WALLS OF SMALL INTESTINE

1. Many ridges and folds

2. Folds covered with villi

a. Tiny, finger like projections

b. Make surface area larger so there are more places for to be absorbed.

Digestive System

D. CHYME IS NOW A SOUP OF MOLECULES READY TO BE ABSORBED THROUGH CELLS ON SURFACE OF VILLI.

1. Molecules of nutrients pass by diffusion and osmosis or by active transport into blood vessels of each villus.

2. Remaining materials are moved into large intestines by peristalsis.

CAPILLARIES AROUND THE VILLUS

Small Intestine

Digestive System

V. ABSORPTION IN LARGE INTESTINE

A. Main job: absorb water from the thin mixture (chyme)

B. Homeostasis is maintained.

C. Peristalsis slows down some.

1. Chyme may stay in large intestine for 3 days

2. Water and sodium are absorbed.

LARGE INTESTINES

Digestive System

D. REMAINING MATERIALS

1. Undigested cellulose2. Bacteria a. Feed on undigested

matterb. Produce vitamins.c. This is an example of

a symbiotic relationship.

Digestive System

E. RELEASE OF SOLIDIFIED WASTES

1. Controlled by muscles in the rectum and anus.

2. Release in the form of feces.

Digestive System

REMEMBER

Food is processed in your digestive system for the purpose of supplying your body with raw materials for metabolism. These raw materials are in the form of nutrients.

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