transport of gases in the blood Flashcards Preview

Respiratory system > transport of gases in the blood > Flashcards

Flashcards in transport of gases in the blood Deck (18):

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
-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
-Ischaemic: Heart disease leads to complications in pumping of blood
-Histotoxic: cells are poisoned so cannot take up oxygen properly


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

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


What the the partial pressure of 02 also known as?

Oxygen tension


Cloride shift

In venous blood:
Movement of bicarbonate ions out of the RBC into plasma
At the same time the chloride ions move into the RBC

At the lungs:
Higher Pa02
Deoxyhaemoglobin releases Co2 and H+
Release of H+ increase concentration of H+ in the RBC
Causes bicarbonate to move back into RBC and cl- to move back out into plasma


Respiratory acidosis/ alkalosis
Metabolic acidosis/ alkalosis

Hypoventilation- decreases the release of C02
This shifts the C02 +H20 = H+ + HCO3- to the right
More H+
So lowers the PH
Leads to respiratory acidosis
More linked to respiratory disease than alkalosis

Respiratory alkalosis- more triggered by central nervous system