transport of gases in the blood Flashcards
Differences between arterial partial pressure of oxygen and arterial content of oxygen?
Arterial partial pressure= partial pressure of gaseos O2 which causes it to dissolve in liquid
-determined by solubility of 02
Arterial content= total amount of 02 in arterial blood
-arterial partial pressure + haemoglobin content
Why do gases not travel in gaseos form in the blood?
Would form bubbles
Leads to Air embolism
02 carried in solution vs haemoglobin
Tissues at rest require 250ml/min of 02
Arterial partial pressure of 02 leads to 3ml/min
C.0. =5l/min
O2 delivered to tissues would be 15 ml/min
Hemoglobin carries 1.34 ml of 02 per per gram
1 Hemoglobin can carry 150g/litre
So total arterial content of 02= 200ml/min
02 supplied to tissues would be 1000ml/min
Tissues at rest only use 25% of available content
Structure of haemoglobin and types
Main type is haemoglobin A= 92%
Other types: Foetal haemoglobin ( gamma chain replaces Beta), HBA2 ( delta chain replaces beta), glycosated haemoglobin
98% of O2 is carries by haemoglobin
The affinity of haemoglobin for 02 depends on PP
Saturation of Hb at different partial pressures of 02
At normal PP of 02= 100mmhg, Hb is almost 100% saturated
At venous PP=40 mmhg , 02 saturation is still 75%
Foetal hemoglobin and myoglobin have higher affinities for 02 at low PP
What chemical changes affect haemoglobin saturation
Lower saturation/ increased dissociation:
- Temperature Increase
- More negative PH
- production of DPG- produced by erythrocytes when blood supply in tissues is low
- increased C02
What does the presence of C0 lead to
C0 has a much higher affinity for haemoglobin compared with 02
It produced carboxyhemoglobin which has an affinity 250 times greater than oxygen
symptoms:
-hypoxia
-anemia
-cherry red cheeky
-Mucous membranes
Does not affect rate of respiration as the PC02 stays the same
What is anaemia
Any condition where the 02 carrying abilities of the blood are reduced.
When tissues are poorly ventilated
RBCs still saturated with 02 but fewer iron binding sites
Different types of hypoxia
- Hypoxic: reduced diffusion of oxygen at the lungs due to a tissue pathology or pressure of atmospheric 02
- Anaemic
- Ischaemic: Heart disease leads to complications in pumping of blood
- Histotoxic: cells are poisoned so cannot take up oxygen properly
- Metabolic
What happens to Co2 breathed in and how can this lead to acid-base disregulation
-7% remains dissolved in the plasma
-23% reacts with deoxyhaemoglobin to form carbamino products
-70% will react with water to from bicarbonate and H+ ions
Bicarbonate can leave the RBCs and enter the plasma in exchange for chlorine
XS H+ can react with deoxyhaemoglobin
What leads to a decrease in pa02 in the blood
Lung dysfunction
The role of CO2 and products in ph control
Usually pH is constant as the Co2 products are breathed out.
When there is a disfunction the ion concentrations can alter the pH:
-Hypoventialtion: XS Co2 so XS H+ =respiratory acidosis
-Hyperventilation: Less C02 so fewer H+ = respiratory alkalosis
What happens to PaO2 in Anaemia
Explain
Stays the same
Pao2 can stay the same when plasma content decrease but not viceversa.
This is because there in no fault in blood transport at the alveoli.
How many litres of 02 are there in blood
3ml in every 1 litre of plasma
200ml In every litre of whole blood
Of this 3ml is soluble in plasma
What is the concentration of plasma 02 dependant on?
- solubility of 02
- partial pressure of gaseseos 02 pushing liquid 02 into the blood
