Session 9

Question 0

What is the function of the Bronchial lung circulation.

Answer 0

Part of the systemic circulation and meets the metabolic needs of the lungs

Question 1

What are the 2 circulations in the lungs?

Answer 1

Bronchial

Pulmonary

Question 2

What is the function of the pulmonary lung circulation?

Answer 2

Blood supply to the alveoli and is needed for gas exchange.

Question 3

What is the pressure in the right atrium?

Answer 3

0-8mmHg

Question 4

What is the pressure in the right ventricle?

Answer 4

15-30mmHg systolic

0-8mmHg diastolic

Question 5

What is the pressure in the pulmonary artery?

Answer 5

15-30mmHg systolic

0-8mmHg diastolic

Question 6

What is the pressure in the left atrium?

Answer 6

1-10 mmHg

Question 7

What is the pressure in the left ventricle?

Answer 7

100-140mmHg systolic

1-10mmHg diastolic

Question 8

What is the pressure in the aorta?

Answer 8

100-140mmHg systolic

60-90mmHg diastolic

Question 9

What is the mean arterial, capillary and venous pressure in the pulmonary circulation?

Answer 9

Arterial - 12-15 mmHg
Capillary - 9-12 mmHg
Venous - 5 mmHg

Question 10

How does the pulmonary circulation ensure low resistance?

Answer 10

Has short and wide vessels
Has many capillaries in parallel
Has very little smooth muscle

Question 11

How does the pulmonary circulation ensure efficient gas exchange?

Answer 11

Has a large surface area due to high density of capillaries in th alveolar wall
Thin layer of tissue to create a short diffusion pathway

Question 12

What does the alveoli need for efficient oxygenation?

Answer 12

Must match the ventilation with perfusion

An optimal Q : V ratio is 0.8 for one alveoli.

Question 13

How can the pulmonary circulation ensure there is an optimal Q : V ratio?

Answer 13

Hypoxia pulmonary vasoconstriction - diverting blood away from the alveoli that are not well ventilated. Possibly due to disease.

Question 14

What can chronic hypoxia vasoconstriction cause?

Answer 14

Right ventricular hypertrophy because increase in vault resistance –> pulmonary hypertension –> right ventricle having to work harder.

Question 15

When can chronic hypoxia vasoconstriction occur?

Answer 15

At high altitudes

Consequence of lung disease

Question 16

What is capillary transit time?

Answer 16

How long it takes for red blood cells to move along a vessel. (Flow)

Question 17

When can capillary transit time decrease?

Extra point - How?

Answer 17

During exercise. There is NO compromise to gas exchange.
Extra point - an increase in cardiac output –> increase in pulmonary arterial pressure –> opening of apical capillaries –> increase O2 uptake of lungs –> increased blood flow –> decreased capillary transit time.

Question 18

What determines fluid formation?

Answer 18

Starlings forces

Question 19

What influences capillary hydrostatic pressure more, arterial or venous pressure in the systemic circulation?

Answer 19

Venous pressure in systemic circulation.

Question 20

What pressure causes fluid to leave pulmonary capillaries?

Answer 20

Hydrostatic pressure

Question 21

What pressure causes fluid to enter pulmonary capillaries?

Answer 21

Colloid oncotic pressure.

Question 22

What happens if the hydrostatic pressure is too high and too much lymph is formed in the lung?

Answer 22

It will impair gas exchange

Question 23

What is the typical movement (in/out) of fluid along a pulmonary capillary?

Answer 23

More fluid moves out at the arterial end

More fluid moves in at the venous end

Question 24

At what atrial pressure will you get oedema?

Answer 24

20-25

Question 25

When could you have high pressure in theft atrium?

Answer 25

Mitral valve stenosis. | Left ventricular failure.

Question 26

What can relieve the symptoms of pulmonary oedema?

Answer 26

Diuretics as they reduce the blood volume which reduces hydrostatic pressure.

Question 27

How does posture effect pulmonary oedemas?

Answer 27

The fluid is at the base of the lung when standing and spread out over the lung when lying down

Question 28

How does the effect of hydrostatic pressure on pulmonary vessels vary with gravity?

Answer 28

Top vessels collapse during diastole Vessels in line with the heart continuously open Vessels at the bottom distend

Question 29

How does the structure of the cerebral circulation secure O2 supply?

Answer 29

Anastomoses between the basilar and internal carotid arteries Circle of willis

Question 30

How can the function of the cerebral circulation ensure secure O2 supply?

Answer 30

The brain stem can regulate other circulations The metabolic factors Myogenic autoregulation

Question 31

How is the cerebral circulation adapted to meet the high demand for O2?

Answer 31

Has a high capillary density so there is a large surface area and slow diffusion rate. Has a high basal flow rate. Has high O2 extraction.

Question 32

How does myogenic auto regulation work?

Answer 32

An increase in blood pressure causes vasoconstriction. A decrease in blood pressure causes vasodilation. Only works above 50mmHg Maintains blood flow with changing pressures.

Question 33

What is Hypercapnia?

Answer 33

An increase in CO2 causes vasodilation

Question 34

What is Hypocapnia? | Extra point - What can cause it?

Answer 34

A decrease in CO2 causes vasoconstriction. | Extra point - By hyperventilation

Question 35

How can regional activity in the cerebral circulation alter blood flow?

Answer 35

Increases the concentrations of metabolites eg K+ which cause vasodilation and therefore an increase in blood flow.

Question 36

What is the Cushings reflex?

Answer 36

It is a response to increase in inter cranial pressure (cold be de to a haemorrhage or tumour) There is an increase in sympathetic output so contraction of arteries occur and increases the arterial blood pressure - maintained cerebral blood flow.

Question 37

When does blood flow in the left coronary artery?

Answer 37

Mainly Diastole.

Question 38

How does the coronary circulation ensure adequate blood flow and O2 supply?

Answer 38

High capillary density Short diffusion pathway - smaller diameter than skeletal capillaries Continuous production of NO by the endothelium which is a vasodilator.

Question 39

What is the relationship between coronary blood flow and myocardial O2 demand?

Answer 39

Almost linear.

Question 40

How can blood flow be increased more in coronary circulation?

Answer 40

Metabolic hyperaemia due to vasodilators such as adenosine, K+, H+

Question 41

What are functional end arteries prone to? | Extra point - What can this cause?

Answer 41

Atheromas Extra point - Stable Angina as blood flow is most during exercise, but diastole is reduced so coronary vessels fill less.

Question 42

What can cause unstable angina?

Answer 42

Stress and cold due to sympathetic vasoconstriction of the coronary vessels.

Question 43

What are vessels in the skeletal circulation rich in?

Answer 43

Innervation by sympathetic vasoconstrictor fibres.

Question 44

How can the skeletal circulation increase O2 and nutrient delivery/removal of metabolites during exercise?

Answer 44

Only half of the vessels are perfused at rest so in exercise there is increased recruitment which allows increased flow and a decreased distance of diffusion.

Question 45

What are the important vasodilation molecules?

Answer 45

``` K+ H+ Inorganic phosphates Osmolality Adenosine ```

Question 46

What causes vasodilation?

Answer 46

Adrenaline acting on beta 2 adrenoreceptors

Question 47

What causes vasoconstriction?

Answer 47

Noradrenaline acting on alpha 1 adrenoreceptors.

Question 48

What is the metabolic requirement of the cutaneous circulation?

Answer 48

Low

Question 49

What is the cutaneous circulation responsible for?

Answer 49

Temperature regulation | Blood pressure maintenance

Question 50

How does the cutaneous circulation control blood pressure?

Answer 50

Vasoconstriction can cause an increase in total peripheral resistance which leads to an increase in arterial pressure.

Question 51

What is Apical skin?

Answer 51

An area that has a high surface area to volume ratio.

Question 52

What structure is in apical skin?

Answer 52

Artereovenous anastomoses. (Glomus body in Spring like shape)

Question 53

How can artereovenous anastomoses regulate heat loss?

Answer 53

They can increase the surface area to volume ratio so more heat is lost.

Question 54

What controls artereovenous anastomoses?

Answer 54

NOT controlled by metabolites Sympathetic vasoconstriction. Decrease in core temperature increases the sympathetic tone. Increase in core temperature decreases the sympathetic tone so relaxation and shunt to Venus plexus.

Question 55

How does non apical skin regulate heat loss?

Answer 55

Has the vasodilator Bradykinin which comes from the ACh sympathetic innervation of sweat glands.