Comparative Vertebrate Physiology Vertebrate Respiration Systems

Respiration systems Gill Lung External invagination High surface area Internal invagination Ventilation

Patterns of air flow Fishes Amphibians Countercurrent flow

Patterns of air flow Birds Mammals Crosscurrent flow Tidal flow

Cutaneous respiration Increase skin surface area Ineffective above 1,000g When PO2 low use reduced lungs Lake Titicaca in Peru

Lamella gills Anatomy Gill arches, filaments, secondary lamellae

Gill ventilation Mouth Buccal cavity (positive pressure) Operculum

Countercurrent flow Is it more efficient?

Ram ventilation Fast swimmers (i.e., tuna, some sharks) Forcing water across gill surface

Aquatic respiration Physiological consequences Variable Density (Kg/l) Viscosity (cPi) O2 diffusion coefficient O2 content Water Air 1.0 0.001 1.14 0.02 0.000025 0.2 1 - 6 210 (ml/L)

Aquatic respiraton Aquatic: 1L water for 1 ml O2 Terrestrial: 25 ml of air for 1 ml O2 It’s harder to breathe under water

Amphibians Varied respiratory systems Positive pressure buccal pump Cutaneous, gills, lungs Positive pressure buccal pump IV phases

Reptiles Negative intrapulmonary pressure All have ribs and intercostal muscles (except chelonians) Crocodiles Muscle contraction

Reptiles Chelonians Rigid carapace (ribs?) and diaphragm Breathe by movement of girdles and muscle contraction

Birds Air sac system Connected to trachea, lungs and long bones One way system

Birds Two breaths to remove air from pathway

Extremes of respiration 1. Increase in altitude PO2 at 5,800 m is 80 mmHg compared with 155 mmHg at sea level Birds migrate at 6,000 m Humans Short-term response: Increase in depth of respiration (not rate), regulated by pH of CSF Long-term response: Increase in erythropoietin and RBC count

Extremes of respiration 2. Diving in air-breathing animals e.g.reptiles, mammals

Extremes of respiration 2. Diving Cope with hypoxia by using all available oxygen High levels of Hb, myoglobin Blood shunt to brain and heart

Extremes of respiration Preventing “the bends” Nitrogen narcosis caused by an increase in pressure

Extremes of respiration Solution: evacuate lungs of air