BISC 101 Lecture Notes - Lecture 13: Fetus, Diastole, Extracellular Fluid
2 Nov 2016
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Document Summary
The medium is the message - air and water provide very different constraints on the design of gas exchange systems. Ventilation = bringing air/water to the gas exchange surface. Gas exchange = exchange of co2 for o2 between the air/water and gas exchange surface. Gas exchange in air: o2 is plentiful, air is less dense and less viscous, ventilations is relatively easy, bi-directional flow, low efficiency. Gas exchange in water: contains 30% less o2, high density/viscosity, energy-demanding to breathe in water, unidirectional, high efficiency. Gas exchange involves ventilation, gas exchange, circulation (usually), and cellular respiration. Many animals lack specialized gas exchange organs and rely on diffusion across body surface (ie. thin walls, large sa, long/thin/flattened body shape) Circulatory systems minimize the distance of diffusion. Gills are out-foldings of the body surface (epithelial cells) suspended in water that increase sa and utilizes ventilation (lungs are infolding cavities)
