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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