Digestive System

Chapter 12

Alimentary Canal

A muscular tube about 9 yards long which passes through the body’s ventral cavity

4 Layers of the Alimentary Canal

1. Mucous Membrane

2. Submucosa: carry materials

3. Muscular Layer: peristalsis

4. Serous Layer: lubrication

Mouth…

Tongue: friction (Papillae-rough projections), taste

Teeth: 20 primary 32

secondary

Palate:

Hard=toward front Soft=tissue near back of throat that forms the cone-shaped projection called the Uvula (“hangy ball”)

Esophagus…

Behind trachea, through diaphragm, lined with mucus

Epiglottis closes over trachea to swallow

Stomach…

Pyloric Sphincter-muscle at junction of esophagus and stomach

A valve that prevents regurgitation of food

Stomach…

Secretes mucus (protection), pepsin (enzyme), hydrochloric acid

Absorbs water, alcohol, and some drugs

Pancreas…

Connects with duodenum

Secretes several enzymes for protein, carb, & DNA digestions

Releases bicarbonate ions to neutralize acid in the small intestine

Liver…

Maintains blood sugar levels (converts glucose to glycogen)

Breaks down proteins (urea)

Storage, detoxification, removes damaged blood cells

Produces bile—helps mix fats with

digested material, increases

absorption of fat-soluble vitamins

Small Intestine…

Duodenum:”C” shaped, connects sm. to stomach

Jejunum:

Ileum: lined with villi (increases surface area)

Small Intestine…

Secretes mucus and watery fluids

Contain digestive enzymes to break down food

Absorption! Active transport/facilitated diffusion

Large Intestine…

Cecum: beginning of lg.

Colon: 4 portions: ascending, transverse, descending, sigmoid

Rectum: anal canal, anus

No digestion

Secretes mucus, absorbs water with electrolytes