DIGESTION the breakdown of food into simpler substances

DIGESTION – the breakdown of food into simpler substances by the body or by a cell.

Intracellular Digestion in Paramecium

Paramecium

Extracellular Digestion in a Gastrovascular Cavity

Alimentary Canals (complete digestive tracts)

The Human Digestive System

Digestive System

MOUTH • Taste Buds • Salivary Glands • Amylase – digests starches PHARYNX – at the back of the mouth; leads to the esophagus and trachea

Adult Mouth

From Mouth to Stomach: the Swallowing Reflex and Esophageal Peristalsis Cardiac sphincter

ESOPHAGUS -about 25 cm/1 ft • peristalsis occurs within to move bolus of food • cardiac sphincter at the end STOMACH • hydrochloric acid breaks down food (in gastric juice) • pepsin digests protein • mucus lining protects • churning of food makes chyme

The Duodenum (Active Hormones) Enterogastrone pyloric sphincter Cardiac sphincter Gastrin • Secretin CCK Secretes Na. HCO 3, pancreatic juices that digest macromolecules

Homeostatic Regulation of Cellular Fuel Pancreas

Secretion of Gastric Juice

Anatomy and Histology of the Stomach

Enzymatic Digestion in the Human Digestive System

SMALL INTESTINE • about 23 feet long in adults • pancreas secretes pancreatic fluid (contains Na. HCO 3) • amylases break down starches • proteases break down proteins • lipases break down fats

Activation of Protein-Digesting Enzymes in the Small Intestine (secreted by pancreas) These proteases cleave bonds adjacent to certain amino acids

The Structure of the Small Intestine

SMALL INTESTINE (con’t) • Liver makes bile to break down fats; it is stored by the gall bladder ; it is what gives solid waste its color • villi – loaded with blood vessels Howdy Ho! LARGE INTESTINE/COLON • about 3 m/9 ft in adults • removes water from waste • waste moves to rectum where it is held before excretion at the anus

Large Intestine (Colon) goblet cells

The Digestive Tracts of a Carnivore (coyote) and a Herbivore (koala) Compared

• Polyps are small growths arising from the epithelial lining that may be benign or cancerous. • Diarrhea and constipation are two common complaints of the large intestine. • Causes of diarrhea include infection of the lower tract and nervous stimulation, both moving feces more rapidly than normal, but also causing dehydration if prolonged.

Ruminant Digestion (removes water) (Boluses enter – microbes break down) (enzymatic digestion) (boluses enter and microbes break down)

List the following in the order in which food would move in the digestive process: esophagus, small intestine, stomach, large intestine, mouth, pharynx, cardiac sphincter.

What activates pepsin in the stomach? Ulcers are caused by. . .

List three substances involved in food digestion and: a. from where they are released ex: amylases from pancreas b. their target ex. duodenum c. what they do ex; digest carbs Compare the function of the small intestine to the large intestine.

The main function of the large intestine is to. . . What is the cecum? The “friendly” bacteria in large intestine function to. .

Food is prevented from entering the trachea because it is blocked by the: Muscular contractions called ____ occur when muscles in the esophagus squeeze the food as it pass through it.

Compare the function of the small intestine to the large intestine.