Respiration - Gas Transport Flashcards
How do gases move in pressure gradients?
move down the pressure gradient
What happens in regards to O2 and CO2 in the pulmonary circuit?
O2 enters blood, CO2 leaves
What happens in regards to O2 and CO2 in the systemic circuit?
O2 leaves blood, CO2 enters.
Why is the pressure gradient for oxygen much bigger than for carbon dioxide?
CO2 is more diffusible
What are the changes in values of PO2 and PCO2 from alveolar air to venous blood in pulmonary capillaries?
Alveolar Air Venous Blood
PO2 100 > 40
PCO2 40 < 46
What are the changes in values of PO2 and PCO2 from tissues to arterial blood in systemic capillaries?
Tissues Arterial Blood
PO2 <40 < 100
PCO2 >46 > 40
How does movement of gas occur in the respiratory system?
diffusion
What properties does the respiration system have that make it good to facilitate gas diffusion?
1) Large surface area for gas exchange.
2) Large partial pressure gradients.
3) Gases with advantageous diffusion properties.
4) Specialised mechanisms for transporting O2 and CO2 between lungs and tissues.
How is oxygen carried in blood?
dissolved
bound to Hb
What is PaO2?
partial pressure of oxygen in arterial blood
What is the amount of dissolved oxygen in blood proportional to?
partial pressure
For each mmHg of PO2, how much oxygen is dissolved in blood?
there is 0.003 ml O2/100 ml blood.
If arterial blood is 100mmHg PO2, how much oxygen is dissolved in blood?
0.3 ml O2/100ml blood (3ml O2/litre of blood).
Why is dissolved oxygen not adequate for body’s requirements?
at rest cardiac output (CO)= 5 L/min.
3ml O2/litre of blood x 5 (CO) = 15ml/min.
BUT tissue requirements at rest 250 ml O2/min.
What is the major transport molecule for oxygen?
haemoglobin
What is the structure of Hb?
four heme (iron porphyrin compounds) groups joined to globin protein
(two α chains and two β
chains polypeptide chains).
What does each heme group contain?
iron in the reduced ferrous
form (Fe+++), which is the
site of O2 binding.
How many Hb molecules are in each red blood cells?
280 million
How long are RBC in the capillary?
1 sec
What does a decrease in pH cause?
a decrease in affinity of haem for oxygen
What does an increase in pH cause?
an increase in affinity of haem for oxygen
What does a decrease in temperature cause?
an increase in affinity of haem for oxygen
What does an increase in temperature cause?
a decrease in affinity of haem for oxygen
At what values does a drop in PO2 not cause drastic effects?
100-60 mmHg
How many oxygens can haem bind and where is their binding sites?
4 and on iron
How much haemoglobin per litre of normal blood?
150g
How many ml of oxygen does one g of Hb combine with?
1.39 oxygen
How much is the total capacity of oxygen? (dissolved+haem)
211mls O2 per litre
What is used to measure O2 and how does it work?
Pulse oximeters used in clinic to measure O2 saturation.
Measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
How much ml per minutes of CO2 is produced?
200ml CO2 /min
How many molecules of CO2 expired by lung for every 100 molecules of O2?
80
What is the ratio of expired CO2 to O2 uptake called?
Respiratory Exchange Ratio
What is the normal respiratory exchange ratio?
0.8
How is CO2 carried in blood?
7% dissolved.
23% bound to
haemoglobin (Hb).
70% converted to
bicarbonate.
What does bicarbonate act as?
buffer
How can acidity be regulated?
Acidity can be regulated by using ventilation to adjust the PCO2.
OR via via kidneys to regulate bicarbonate levels
What is the equation for bicarbonate?
H2O + CO2 ⇌ H2CO3 ⇌ (H+) + HCO3-
In the equation for bicarbonate, what system is the forward reaction (right)?
systemic
In the equation for bicarbonate, what system is the backward reaction (left)?
pulmonary
