Chapter 13: Respiratory Physiology and Gas Exchange

Respiratory Physiology and Gas Exchange outlines the physical properties of gases, including partial pressure and solubility, and applies these principles to Fick’s law to explain gas exchange efficiency. Respiratory surfaces are evaluated for their surface area, thickness, and permeability, with examples like gills in fish, tracheal systems in insects, and alveoli in mammals. Ventilation mechanisms such as tidal flow, unidirectional flow, and crosscurrent exchange are explored in animals like mammals, birds, and amphibians. The chapter also addresses oxygen transport via respiratory pigments, focusing on hemoglobin and its oxygen-binding properties—cooperativity, Bohr and Root effects, and allosteric modulation. Carbon dioxide transport is explained through bicarbonate buffering, chloride shift, and enzymatic catalysis by carbonic anhydrase. Neural and chemical control of respiration is discussed, including chemoreceptors and feedback loops that regulate breathing in response to CO₂ and O₂ levels. Comparative examples show how diving mammals, high-altitude species, and ectotherms adapt respiratory systems to extreme conditions. The chapter concludes by connecting respiratory function to circulation and metabolism, emphasizing its central role in maintaining homeostasis across varied ecological contexts.