1. Comparative Vertebrate Physiology
An overview of digestion

2. Feeding strategies
Filter feeders
Marine mammals and birds

3. Feeding strategies
Seizing of prey

4. Why have a digestive tract?
Unicellular animals digest intracellularly
Disadvantages
Limits size of prey
Each cell must be designed to undertake digestion
Extracellular (vertebrates)
Allows the ability to feed on larger prey
Only certain cells can digest

5. Overview Anatomical areas Headgut (mouth, pharynx)
Foregut (esophagus, stomach)
Midgut (small intestine)
Hindgut (colon)

6. Functions 1. Ingestion – mouth 2. Motility Maintain muscle tone
A. Propulsive movement: unidirectional
B. Mixing movement: bidirectional

7. Functions 3. Digestion • Mechanical
Mouth (chewing), stomach (churning), small intestine (segmentation)
• Chemical
Passage across plasma membranes
Carbohydrates: tri-, disaccharides to mono-
Proteins: into amino acids
Fats: monoglycerides and fatty acids

8. Functions
4. Secretion
Mouth, stomach, liver, pancreas, small intestine
5. Absorption
80% in the duodenum, rest in small and large intestine
6. Elimination of wastes

9. Accessory glands Salivary glands
Moisten, lubricate, breakdown saccharides
Pancreas
Enzymes secreted into duodenum
Liver
Neutralizes stomach acid, breakdown fats
Gall bladder
Store of bile

10. Absorption
Intestinal villi and microvilli