Digestive System What is digestion The breaking down

Digestive System

What is digestion? • The breaking down of foods into simpler substances called nutrients.

The purpose of saliva • Contains a chemical substance called ptyalin. This breaks starch into sugars. • Moistens food.

Mechanical Digestion • The physical action of breaking down food into smaller parts. • Begins in the mouth with the teeth.

Role of Structures in the Digestive System

Mouth • Food enters the digestive system here. • Chemical and mechanical digestion occurs here.

Epiglottis • Flap of tissue that closes over the windpipe when you swallow.

Esophagus • Connects the mouth and the stomach. • Carries food to the stomach by peristalsis.

Stomach • Mechanical (churning) and chemical digestion (pepsin and hydrochloric acid) occur here. • Peristalsis pushes food toward the stomach’s exit.

Small Intestine • Food moves through this organ by peristalsis. • Most food is chemically digested here

Liver • Produces bile and stores it in the gall bladder. • Bile breaks down fats. • Food does NOT go in here…digestive helper to the small intestine

Gall bladder • Stores bile made by the liver • Food does NOT go in here…digestive helper to the small intestine

Pancreas • Produces pancreatic juices that break down proteins, starches and fats. • Food does NOT go in here…digestive helper to the small intestine

Peristalsis • Waves of muscular contractions that move food through the digestive system. • Occurs in esophagus, stomach and small intestine.

Mucus • Mucus coats and protects the stomach walls from the hydrochloric acid (HCL).

Most of the Digestion • Takes place in the small intestine.

Absorption of Food

Absorption in the small intestine • Absorption is the process by which digested food nutrients pass through the walls of the villi and enter the bloodstream.

Purpose of Villi • Villi increase the surface area of the small intestine and increase the rate of nutrient absorption into the blood.

Role of Large Intestine • Most water is absorbed from the undigested foods. • Helpful bacteria in the large intestine produce vitamins K and B that are needed by the body.

Purpose of Rectum • Stores solid wastes produced by the body.

Purpose of Anus • Allows solid waste to leave the body (it is an opening).