BIOL 205 Lecture Notes - Lecture 34: Countercurrent Exchange, Viscosity, Surface Layer
7 Sep 2016
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Respiratory surfaces for gas exchange: tracheal system, lungs and gills: tracheal system, present in insects, extensive branching tube system open to outside, through narrow pores spiracles, series of balloon shaped air sac. 4: every part of the body is exposed to atmospheric o2. In birds: series of lungs, 2 cycles of inhalation and exhalation (2 breaths, air inhaled to posterior sacs, air flows to lungs gas exchange, air flows from lungs anterior sacs, posterior filled, anterior sacs air is expulsed. In mammals: air comes in through trachea and enter bronchi. Lead to bronchioles several alveoli: requires close proximity of blood. Larger body size = larger respiratory surface area. 3: series of feather like structures, more elaborate flow system than tuft gills. Lamellar gills: highly elaborated in fishes, pairs of gill arches which stand vertically, each carries number of paired filaments, thrown into series of vertical flaps. Lamellae: water flows over surface of filament & between lamellae, arches are hollow.
