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Transcript
Comparative Vertebrate
Physiology
An overview of digestion
Feeding strategies

Filter feeders

Marine mammals and birds
Feeding strategies
Seizing of prey
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
Overview
Anatomical areas
Headgut (mouth, pharynx)
Foregut (esophagus, stomach)
Midgut (small intestine)
Hindgut (colon)
Functions
1. Ingestion – mouth
2. Motility
Maintain muscle tone
A. Propulsive movement: unidirectional
B. Mixing movement: bidirectional
Functions
3. Digestion
• Mechanical
Mouth (chewing), stomach (churning), small intestine
(segmentation)
• Chemical
Passage across plasma membranes
Carbohydrates: tri-, disaccharides to monoProteins: into amino acids
Fats: monoglycerides and fatty acids
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
Accessory glands
Salivary glands
Moisten, lubricate, breakdown saccharides
Pancreas
Enzymes secreted into duodenum
Liver
Neutralizes stomach acid, breakdown fats
Gall bladder
Store of bile
Absorption
Intestinal villi and microvilli