Biology: Human Physiology: Digestive System

Alimentary Canal

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STOMACH

SMALL INTESTINE

LARGE INTESTINE

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ANUS

- Secretes gastric juice

- Digestive fluid mixes with the food

- HCL breaks down food and exposes peptide bonds + kills most bacteria

- Pepsin breaks peptide bonds

Chemical digestion: pepsin + HCL

Mechanical digestion: peristalsis

- Smooth muscles control

- Controlled by autonomic nervous system

- Two layers of muscle

- circular

- longitudinal

- Movement of food = peristalsis

- Digestion is completed here

- Products are absorbed into the blood stream

- Content enters the first part, where bile (from the gallbladder and liver) enters

- The small intestine has villi which increases surface area

- Main function is to reabsorb water

- Long and folded to maximise absorption

- Mucus is secreted for lubrication and aids the movement of feces

- Villi increase surface area for absorption

- Villi have microvilli which have protein pumps

- Absorb food by active transport and facilitated diffusion

- Villi have one layer of epithelial cells which lead to easier absorption

- Blood capillaries are near the surface which minimizes the distance the molecules have to travel

- Lymph vessels (lacteal) near the surface which allows for easy absorption of lipids

Pancreas and Digestine

Pancreas produces enzymes that aid digestion

- Lipase - hydrolizes lipids to glycerol and fatty acids

- Amylase - hydrolizes starch to maltose

- Trypsin - hydrolizes large polypeptides to small polypeptides