Pulmonary blood flow, gas exchange and transport 1-3

Question 1

What are the 2 blood supplies to the lungs?

Answer 1

Bronchial circulation (nutritive) and pulmonary circulation (gas exchange)

Question 2

What is bronchial circulation to the lungs?

Answer 2

Supplied via the bronchial arteries arising from systemic circulation from left side of heart to supply oxygenated blood to lungs

Question 3

What is pulmonary circulation (gas exchange)?

Answer 3

Carries deoxygenated blood from the RV of the heart to the lungs then returns oxygenated blood to LA of heart

Question 4

What system is pulmonary circulation?

Answer 4

High flow, low pressure

Question 5

What is the relationship between ventilation and perfusion?

Answer 5

Ventilation (air getting to alveoli L/min) should be ideally the same as perfusion (local blood flow L/min)

Question 6

What is the distribution of blood flow in the lungs influenced by?

Answer 6

Hydrostatic (blood) pressure and alveolar pressure

Question 7

Where in the lungs is there an imbalance in the ventilation-perfusion ratio?

Answer 7

Base and apex

Question 8

Ventilation-perfusion ratio at the base of the lung

Answer 8

Blood flow is high because arterial pressure exceeds alveolar pressure so perfusion>ventilation

Question 9

Ventilation-perfusion ratio at the apex of the lung

Answer 9

Blood flow is low because arterial pressure is less than alveolar pressure so perfusion

Question 10

Where does the majority of ventilation perfusion mismatch occur in the lungs?

Answer 10

Apex

Question 11

What is autoregulation in V/Q mismatch?

Answer 11

Occurs when ventilation

Question 12

What is shunt?

Answer 12

Blood that flows through a poorly ventilated region without being oxygenated (perfused but not ventilated)

Question 13

Local control mechanism for shunt

Answer 13

Tissue around under-ventilated alveoli constrict their arterioles, diverting blood to better ventilated alveoli

Question 14

What is autoregulation known as when ventilation>blood flow?

Answer 14

Alveolar dead space (oxygen gets into alveoli but not enough blood flow for gas exchange)

Question 15

What is the rate of diffusion DIRECTLY proportional to?

Answer 15

Partial pressure gradient
Gas solubility
Available surface area

Question 16

What is the rate of diffusion INVERSELY proportional to?

Answer 16

Thickness of the membrane

Question 17

Why are the diffusion rates of O2 and CO2 so similar even though the partial pressure gradient of O2 is much bigger?

Answer 17

CO2 is more soluble in water so diffuses faster

Question 18

What is physiological dead space?

Answer 18

Alveolar + anatomical dead space

Question 19

How many ml of O2 per litre of plasma?

Answer 19

3ml

Question 20

What does haemoglobin increase the O2 carrying capacity of whole blood to?

Answer 20

200ml

Question 21

What is the O2 demand of resting tissues?

Answer 21

250ml/min

Question 22

What percentage of arterial O2 is extracted by peripheral tissues?

Answer 22

25% at rest

Question 23

How can a reduced PO2 affect saturation of RBCs?

Answer 23

Halve RBC saturation

Question 24

What is the arterial partial pressure of O2?

Answer 24

It refers to the O2 in solution and is determined by O2 solubility and the partial pressure of O2 in the gaseous phase that is driving O2 into solution

Question 25

What is the partial pressure that’s driving O2 into the liquid phase in plasma?

Answer 25

100mmHg (O2 solubility - 0.03ml/L/mmHg; 3ml O2/L plasma so 3/0.03 = 100)