Chapter 23 Outline

Chapter 23 Outline

Fundamental Concepts of External Respiration

Principles of Gas Exchange by Active Ventilation

  • The O2 partial pressure in blood leaving a breathing organ depends on the spatial relation between the flow of the blood and the flow of the air or water
  • Arterial CO2 partial pressures are much lower in water breathers than air breathers
  • BOX 23.1 Capacitance Coefficients Explain the Relative Partial Pressures of O2 and CO2 in Arterial Blood

Low O2: Detection and Response

Introduction to Vertebrate Breathing

Breathing by Fish

  • Gill ventilation is usually driven by buccal–opercular pumping
  • Many fish use ram ventilation on occasion, and some use it all the time
  • Decreased O2 and exercise are the major stimuli for increased ventilation in fish
  • Several hundred species of bony fish are able to breathe air

Breathing by Amphibians

  • Gills, lungs, and skin are used in various combinations to achieve gas exchange

Breathing by Reptiles Other than Birds

Breathing by Mammals

  • The total lung volume is employed in different ways in different sorts of breathing
  • The gas in the final airways differs from atmospheric air in composition and is motionless
  • The forces for ventilation are developed by the diaphragm and the intercostal and abdominal muscles
  • The control of ventilation
  • BOX 23.2 Mammals at High Altitude, With Notes on High-Flying Birds
  • In species of different sizes, lung volume tends to be a constant proportion of body size, but breathing frequency varies allometrically
  • Pulmonary surfactant keeps the alveoli from collapsing

Breathing by Birds

  • Ventilation is by bellows action
  • Air flows unidirectionally through the parabronchi
  • BOX 23.3 Bird Development: Filling the Lungs with Air Before Hatching
  • The gas-exchange system is cross-current

Breathing by Aquatic Invertebrates and Allied Groups

  • Molluscs exemplify an exceptional diversity of breathing organs built on a common plan
  • Decapod crustaceans include many important water breathers and some air breathers

Breathing by Insects and Other Tracheate Arthropods

  • BOX 23.4 The Book Lungs of Arachnids
  • Diffusion is a key mechanism of gas transport through the tracheal system
  • Some insects employ conspicuous ventilation
  • Microscopic ventilation is far more common than believed even 15 years ago
  • Control of breathing
  • Aquatic insects breathe sometimes from the water, sometimes from the atmosphere, and sometimes from both
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