Comparative Anatomy and Physiology of Animals
Lecture 8 Oxygen Transport and Blood Acid-Base Balance 03/11/20
Respiration in Vertebrates
- Principles of gas exchange by active ventilation
- Rate of oxygen uptake depends on 1) volume flow of air or water per unit time, and 2)
amount of O2 removed from each unit volume
Red blood cells (erythrocytes)
- Vary in size and shape in vertebrates.
- All species except mammals have nucleated red blood cells
- All contain haemoglobin
- Produced in bone marrow under hormonal control (haemopoietin produced in kidneys)
Oxygen transport
- Only one O2 molecule can bind to a haem group at a time
- 20mL O2 per 100 mL blood
- Oxygen saturation = % of binding sites filled
Oxygen transport and release
Oxygen transport during exercise
- pO2 of the blood leaving a particular tissue (venous reserve) depends on: Rate of blood flow
through the tissue, arterial pO2, amount of haemoglobin per unit of blood volume, and
tissue’s rate of oxygen consumption
- Blood passes through lungs faster reducing the time for equilibrium between air and blood
so blood pO2 leaving the lungs decreases but O2 content is hardly affected
Oxygen transport
- Binding capacity is enhanced by the presence of oxygen that is already bound –
cooperativity. This shifts the line to the right.
- Oxygen equilibrium curves vary: in shape because of various molecular forms of
haemoglobin in different species, and in height which reflects the amount of haemoglobin
present in the blood.
, Oxygen affinity
- P50 is an index of the affinity of a
respiratory pigment to O2
- P50 is the partial pressure in the blood
at 50% oxygen saturation
- A shift to the right leads to a reduced
O2 affinity
Bohr effect
- Decrease in pH reduces oxygen affinity and shifts oxygen equilibrium curve to the right.
Oxygen affinity
- An increase in temperature decreases oxygen affinity and shifts oxygen equilibrium curve to
the right.
- Blood at high temperatures can carry more oxygen at saturation.
- A decrease in pH reduces the oxygen-carrying capacity of haemoglobin in eels.
CO2 transport
- Dissolved in the blood plasma as CO2 molecules but is only a fraction is as a dissolved gas.
- Forms carbonic acid when dissolves in aqueous solution. Bicarbonate ions can also dissociate
into a hydrogen ion and a carbonate ion
- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
Lecture 8 Oxygen Transport and Blood Acid-Base Balance 03/11/20
Respiration in Vertebrates
- Principles of gas exchange by active ventilation
- Rate of oxygen uptake depends on 1) volume flow of air or water per unit time, and 2)
amount of O2 removed from each unit volume
Red blood cells (erythrocytes)
- Vary in size and shape in vertebrates.
- All species except mammals have nucleated red blood cells
- All contain haemoglobin
- Produced in bone marrow under hormonal control (haemopoietin produced in kidneys)
Oxygen transport
- Only one O2 molecule can bind to a haem group at a time
- 20mL O2 per 100 mL blood
- Oxygen saturation = % of binding sites filled
Oxygen transport and release
Oxygen transport during exercise
- pO2 of the blood leaving a particular tissue (venous reserve) depends on: Rate of blood flow
through the tissue, arterial pO2, amount of haemoglobin per unit of blood volume, and
tissue’s rate of oxygen consumption
- Blood passes through lungs faster reducing the time for equilibrium between air and blood
so blood pO2 leaving the lungs decreases but O2 content is hardly affected
Oxygen transport
- Binding capacity is enhanced by the presence of oxygen that is already bound –
cooperativity. This shifts the line to the right.
- Oxygen equilibrium curves vary: in shape because of various molecular forms of
haemoglobin in different species, and in height which reflects the amount of haemoglobin
present in the blood.
, Oxygen affinity
- P50 is an index of the affinity of a
respiratory pigment to O2
- P50 is the partial pressure in the blood
at 50% oxygen saturation
- A shift to the right leads to a reduced
O2 affinity
Bohr effect
- Decrease in pH reduces oxygen affinity and shifts oxygen equilibrium curve to the right.
Oxygen affinity
- An increase in temperature decreases oxygen affinity and shifts oxygen equilibrium curve to
the right.
- Blood at high temperatures can carry more oxygen at saturation.
- A decrease in pH reduces the oxygen-carrying capacity of haemoglobin in eels.
CO2 transport
- Dissolved in the blood plasma as CO2 molecules but is only a fraction is as a dissolved gas.
- Forms carbonic acid when dissolves in aqueous solution. Bicarbonate ions can also dissociate
into a hydrogen ion and a carbonate ion
- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
