Special Circulations

Question 1

Pulmonary circulation must accept the

Answer 1

Entire cardiac output

Question 2

Pulmonary circulation works at

Answer 2

Low pressure and low resistance

Question 3

Features of the pulmonary circulation

Answer 3

Low resistance- short wide vessels, lots of capillaries, arterioles have relatively little smooth muscle so lumen size T not constricted as much

Question 4

Mean arterial pressure

Answer 4

12-15mmHg

Question 5

Mean capillary pressure

Answer 5

9-12mmHg

Question 6

Mean venous pressure

Answer 6

5mmHg

Question 7

Adaptations of pulmonary circulation for efficient gas exchange

Answer 7

very high density of capillaries in alveolar wall - large sa

Short diffusion distance

Question 8

What is V/Q

Answer 8

Ventilation perfusion ratio

Need to match for efficient oxygenation

Ideal = 0.8

Question 9

How do you maintain V/Q

Answer 9

Diverting blood from alveoli which are not well ventilated

Question 10

What is the most important mechanism ensuring optimal ventilation perfusion ratio

Answer 10

Hypoxia pulmonary vasoconstriction - regulates pulmonary vascular tone

Alveolar hypoxia results in vasoconstriction of pulmonary vessels

Question 11

Poorly ventilated alveoli are less well perfused to optimise gas exchange. Effect is opposite to

Answer 11

That in systemic circulation

Question 12

Chronic hypoxic vasoconstriction can cause

Answer 12

Right ventricular failure or chronic pulmonary hypertension

e.g. altitude or emphysema

Question 13

Chronic increase in vascular resistance leads to

Answer 13

Chronic pulmonary hypertension

Question 14

High afterload on right ventricle can lead to

Answer 14

Right ventricular heart failure

Question 15

low pressure pulmonary vessels are strongly influenced by

Answer 15

Gravity

In upright position there is greater hydrostatic pressure on vessels in lower part of lung

Question 16

Effect of exercise on pulmonary blood flow

Answer 16

Increased cardiac output
Small increase in pulmonary arterial pressure
Opens apical capillaries
Increase oxygen uptake by lungs
Capillary transit time is reduced as blood flow increases

Question 17

Features of tissue fluid formation

Answer 17

Starling forces
Hydrostatic pressure pushes fluid out
Oncotic pressure draws fluid in (created by plasma proteins)

Question 18

Capillary hydrostatic pressure is influenced more by

Answer 18

Venous pressure in the systemic circulation

Question 19

Hypertension does not usually result in

Answer 19

Peripheral oedema

Question 20

low capillary pressure minimises the formation of

Answer 20

Lung lymph

Question 21

Increased capillary pressure causes

Answer 21

More fluid to filter out and oedema

Question 22

Can get pulmonary oedema if

Answer 22

Capillary pressure increases (left atrial pressure rises to 20-25mmHg, mitral valve stenosis and left ventricular failure)

Question 23

Principles of pulmonary oedema

Answer 23

Impairs gas exchange 
Forms mainly at base when upright 
Forms throughout lung when lying down 
use diuretics to relieve symptoms 
Treat underlying cause

Question 24

Worse type of pulmonary oedema

Answer 24

Forms throughout lung when lying down