Comparative Vertebrate Physiology

Vertebrate Respiration Systems

Respiration systems

Gill External invagination High surface area

Lung Internal invagination Ventilation

Patterns of air flowAmphibiansFishes

Countercurrent flow

Patterns of air flowMammalsBirds

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?

100 90 80 70

50 60 70blood

water

40

Unidirectional

90 80 70

80 70 60

water

blood

100

90

Counter directional

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

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