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