PNB 2250 Lecture Notes - Lecture 5: Countercurrent Exchange, Trachea, Vascular Plant
9 Sep 2016
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Practical requirements: negative or positive pressure systems, pathways for air movement, respiratory membrane. General characteristics: very thin membranes (like gills, large surface area (like gills, lots of blood flow. There are no proteins that effectively pump gases: can be paired organs, ventilation- accelerates gas exchange. Adaptations: skin, trachea & lungs, advantages and disadvantages to each, suited to the environment, positive correlation between ability to obtain oxygen and an animal"s metabolic rate, gills are poorly suited because of lack of buoyancy and dryness. Fish die out of water because gills collapse, not because there isn"t enough oxygen. No ventilation: must stay moist, extensive, vascularized. Water is needed to prevent tissue from drying out and cracking. Somewhat of a countercurrent flow: reptiles (sea snakes, mammals (trivial) Insects: have a diffusive system, neither positive or negative pressure system, limited ventilation, series of hollow pipes (trachea) throughout an insects body.
