User:Yunz05/Organs of the Alimentary Canal

A. Physical Digestion

1. Breakdown of large pieces of food into smaller ones

a. Grinding

b. Chewing

2. Exposes more surface area to chemical digestion

B. Chemical Digestion

1. Enzymes break complex molecules into simpler ones

C. Intracellular Digestion

1. Digestion that occurs inside of a cell

a. Plant cells

b. Unicellular organisms

D. Extracellular Digestion

1. Digestion takes place outside of cells

2. Cells secrete enzymes into a digestive cavity

E. Endocytosis

1. Pinocytosis

a. “Cell drinking” - Infolding of cell walls takes in large

molecules

2. Phagocytosis

a. “Cell eating” - Cells surrounds and absorbs food

An Overview of Human Digestion

A. Oral Cavity

1. Chewing

2. Saliva moistens food

3. Saliva contains enzymes

B. Esophagus

1. Moves food to the stomach by peristalsis

C. Stomach

1. Sphincters control movement of food into and out of the stomach

2. Stomach glands release gastric juices

a. water, enzymes, mucus, acid

3. Most food moves on to the small intestine within 4 hours

D. Small Intestine

1. Liver and pancreas secrete enzymes into the small intestine

2. Digestion is completed

3. Nutrients are absorbed through the intestinal walls

E. Large Intestine

1. Bacteria produce some vitamins

2. Vitamins absorbed into bloodstream

3. Water is reabsorbed

4. Feces move on to the rectum

Carbohydrate Digestion

A. Mouth

1. Salivary amylase breaks starch into sugar starch + water and sugar (maltose)

B. Stomach

1. pH is too low for amylase to work

C. Small Intestine

1. Pancreatic juices neutralize stomach acids

2. Intestinal and pancreatic enzymes complete carbohydrate digestion

Protein and Fat Digestion

A. Protein Digestion

1. Mouth

a. Only mechanical digestion occurs

2. Stomach

a. Hormone gastrin signals stomach to secrete acid

b. Acid converts pepsinogen to protein digesting enzyme pepsin

3. Small Intestine

a. Pancreas secretes trypsin into small intestine

b. Trypsin and other enzymes secreted by sm. int. digest protein into amino acids

B. Fat Digestion

1. Mouth and Stomach

a. Only mechanical digestion occurs here

2. Bile from liver (stored in gall bladder) emulsifies fat

3. Lipase from pancreas splits fat into fatty acids and glycerol

Absorption

A. End Products of Digestion

1. Proteins

a. Amino acids

2. Starches

a. Simple sugars

3. Fats

a. Glycerol

b. Fatty acids

Can You Guess All the Parts of The Digestive System?