DIGESTION – the breakdown of food into simpler substances by the body

Extracellular digestion in a gastrovascular cavity

Intracellular digestion in Paramecium

Paramecium

Alimentary Canals

The Human Digestive System

Digestive System

Adult Mouth

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

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 Gastrin Secretin CCK Secretes NaHCO 3, pancreatic juices that digest macromolecules pyloric valve

Homeostatic Regulation of Cellular Fuel

Secretion of Gastric Juice

Anatomy and Histology of the Stomach

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

Enzymatic Digestion in the Human Digestive System

Activation of Protein-Digesting Enzymes in 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 LARGE INTESTINE/COLON about 3m/9 ft in adults removes water from waste waste moves to rectum where it is held before excretion at the anus Howdy Ho!

The Structure of the Small Intestine

Large Intestine (Colon)

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.

Water and fiber in the diet can prevent constipation where the feces become too dry and hard. Hemorrhoids are enlarged and inflamed blood vessels at the anus; this condition is associated with chronic constipation. Regular elimination reduces the time the colon wall is exposed to cancer- promoting agents in the feces and may help prevent cancer.

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