BIOS 1710 Animal Digestion

Three sections of the digestive system and their primary functions

Stomach: mixes food with acid and enzymes; Small intestine: finishes digestion and absorbs nutrients; Large intestine: absorbs water and holds feces

Organs of the digestive system - primary functions

Each organ handles transport, storage, mechanical/chemical digestion, or absorption; produces enzymes, acids, and bile for digestion.

What chemical substances are produced and what do they do?

Acids and enzymes in stomach break down food; bile emulsifies fats; pancreatic juices neutralize acid and digest nutrients.

Which organs do archosaurs have that humans don’t?

Archosaurs (birds, crocs) have a crop, proventriculus, and gizzard—used for food storage and mechanical digestion.

Four types of mammalian teeth and their functions

Incisors: clipping; Canines: puncture/tear; Premolars: shearing; Molars: grinding.

Definition of circular folds

Deep folds of the mucosa and submucosa that increase surface area for nutrient absorption.

Definition of villi

Highly folded inner surfaces in the small intestine (jejunum and ileum) that increase absorption area.

Definition of microvilli

Microscopic fingerlike projections on epithelial cells that further increase surface area.

Definition of emulsification

Breaking large clusters of fats into smaller lipid droplets for easier enzyme access.

Peristalsis definition

Waves of muscular contraction that move food toward the base of the stomach.

How is stomach movement/emptying controlled?

Three muscle layers move in all directions; constant contraction rate but variable strength; sphincters control entry and exit.

Secretin feedback loop

Secretin is released in response to acidic chyme entering duodenum; stimulates pancreas to release bicarbonate ions to neutralize acid.

Cholecystokinin feedback loop

CCK is released when fats enter duodenum; causes gallbladder to release bile.

Why break down food so much?

Nutrients must be absorbed at the molecular level; large food molecules cannot cross membranes.

Where are sphincters found and what do they do?

Located at entry and exit of stomach; keep contents in until ready to move on.

Why does the small intestine have high surface area and how?

To maximize absorption; achieved with long length, circular folds, villi, and microvilli.

Why does the ileum have a lot of immune tissue?

Because it’s near the large intestine, where bacterial load is highest, so immune defense is necessary.

Where do you find most of your gut flora and what do they do?

In the large intestine; they break down undigested carbohydrates and produce useful compounds.

Where are most nutrients, vitamins, and water absorbed?

Nutrients and vitamins in the small intestine; water mainly in the large intestine.