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