7 Digestion 1 Exchange with Environment

7 Digestion 1 Exchange with Environment - 2 to diffuse from...

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Digestion I. Exchange with the environment II. Malnourishment and Overnourishment III. Digestive organs IV. Process of digestion and absorption A. Carbohydrates B. Proteins C. Lipids D. Absorption of water
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Fig. 40.3 Exchange 0.15 mm (a) Single cell 1.5 mm (b) Two layers of cells Exchange Exchange Mouth Gastrovascular cavity Exchange with the Environment (amoeba) (hydra)
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As body size increases, there are limits to diffusion: t = x 2 /2D t = time it takes to diffuse a distance x (sec) x = diffusion distance (cm) D = diffusion constant (much larger for air than water) • Hydra: How long does it take for O 2 to diffuse from its gastrovascular cavity across a cell? x = ~ 2 mm (approx. thickness of one cell) t = (.0002cm) 2 / 2 (1X10 -5 cm 2 /sec) = 0.002 sec (2 msec) • Human arm: How long does it take for O
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Unformatted text preview: 2 to diffuse from its dorsal to its ventral side? x = ~ 3 cm (thickness) t = (3 cm) 2 /2 (1 X 10-5 cm 2 /sec) = 450,000 sec = 5.2 days!! Solutions in Complex Animals: Increase surface area for diffusion via folded or branched internal surfaces Circulatory system to shuttle materials along exchange surfaces Fig. 40.4 0.5 cm Nutrients Digestive system Lining of small intestine Mouth Food External environment Animal body CO 2 O 2 Circulatory system Heart Respiratory system Cells Interstitial fluid Excretory system Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) Kidney tubules 10 m 50 m Lung tissue Internal Exchange Surfaces of Complex Animals...
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7 Digestion 1 Exchange with Environment - 2 to diffuse from...

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