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pulmonary circulation Flashcards

1
Q

what are the 2 circulations in the lung?

A

pulmonary and bronchial

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2
Q

what circulation is the bronchial circulation part of?

A

systemic circulation

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3
Q

what does the bronchial circulation supply?

A

capillary beds in the trachea and bronchi smooth muscle

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4
Q

where do bronchial arteries branch off from?

A

early parts of the descending aorta

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5
Q

where does the bronchial venous drainage drain into?

A

bronchial veins in the right atrium

pulmonary veins going into the left atrium

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6
Q

where are the bronchial arteries found?

A

travelling along the main bronchi

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7
Q

how long does it take for blood to pass through the lungs?

A

5 seconds

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8
Q

what is the surface area of the lungs?

A

50-100m2

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9
Q

what are the special anatomical features of the pulmonary circulation?

A

thin walled pulmonary arteries
large diameter
highly distensible

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10
Q

what letter represents blood flow?

A

Q

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11
Q

give an equation to calculate blood flow

A

pressure gradient/resistance

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12
Q

which has lower pressure; the pulmonary or systemic circulation?

A

pulmonary

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13
Q

how does the blood flow equation show that pulmonary resistance is low?

A

pulmonary circulation has the same blood flow as the systemic circulation

pulmonary circ has a lower pressure than the systemic circulation

to make blood flow the same, the pulmonary circulation needs to have a lower resistance

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14
Q

what happens if pulmonary arterial resistance rises?

A

pulmonary arterial hypertension

right heart enlarges and eventually fails

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15
Q

which nerve supply carries pain and touch sensation from the lungs and to what spinal level does it go?

A

somatic nerve supply

to T2-T6

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16
Q

where does the sympathetic nerve supply of the lungs originate from?

A

T2 to T4-6

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17
Q

which part of the lungs do the sympathetic nerves innervate?

A

smooth muscle in the bronchial walls and small pulmonary vessels

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18
Q

what action do the sympathetic nerves innervating the lungs bring about?

A

bronchodilation and vasodilation

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19
Q

what receptors and neurotransmitter cause bronchial smooth muscle to relax and dilate?

A

adrenergic beta receptors

noradrenaline

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20
Q

what nerve delivers parasympathetic innervation to the lungs?

A

the vagus

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21
Q

what action do the efferent parasympathetic fibres innervating the lungs cause?

A

bronchoconstriction

stimulates secretion of mucus in the bronchi

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22
Q

where does gas exchange in the lungs occur?

A

alveolar ducts and alveoli

and to the respiratory bronchioles to a small extent

23
Q

when upright, which part of the lungs has the lowest pressure?

A

the base

24
Q

why is the base of the lung well perfused when upright?

A

gravity helps blood circulate because pulmonary blood pressure is low

25
Q

describe the blood flow in zone 1 of the lungs and explain it

A

intermittent flow - Pa > PA > Pv

pressure varies during inspiration and expiration

flow ceases during expiration when lung pressure is at its maximum

alveoli squash the capillaries flat and blocks them bc they’re at a higher pressure

26
Q

when is total cessation of flow in the apices seen?

A

when a person is ventilated with positive pressure or haemorrhage

27
Q

where is zone 2 of the lungs?

A

3cm above the heart

28
Q

describe the flow of blood in zone 2 of the lungs and explain it?

A

pulsatile flow; Pa > PA > Pv

flow fluctuates during inspiration and expiration bc of changes in alveolar pressure

flow greater in systole than diastole

29
Q

what part of the lungs is zone 3?

A

the base

30
Q

describe and explain the flow of blood in zone 3 of the lungs

A

continuous blood flow because the arterial and venous pressure always exceed alveolar pressure

Pa > Pv > PA

31
Q

what is radioactive xenon used for and how?

A

measuring the distribution of blood flow in the upright lung

xenon injected into the venous blood
enters into the alveolar gas from pulmonary capillaries
radiation counters measure amount of xenon passing through each lung

32
Q

what letter represents lung compliance?

A

C

33
Q

what is lung compliance?

A

measure of stretchability of the lungs

34
Q

how is lung compliance measured?

A

the change in volume per unit pressure change

C = dV/dP

35
Q

when is the work of breathing lowest?

A

when a given change in pressure gives the largest change of volume

36
Q

which part of the lungs has the highest compliance?

A

the base

37
Q

at the base of the lungs, which is larger; Q or V?

A

Q

38
Q

at the apex of the lungs, which is larger; Q or V?

A

V

39
Q

describe the gas content of blood in the apex and the base?

A

apex - high PO2 and low PCO2 bc good gas exchange but little blood flow

base - low PO2 and high PaCO2 bc little ventilation

40
Q

what is the V/Q ratio in conditions of airway obstruction

A

lower than normal

41
Q

what is the V/Q ratio in conditions of blood flow obstruction?

A

higher than normal

42
Q

give an example of a blood flow obstruction

A

embolism

43
Q

what does pulmonary hypoxia cause and how does this help?

A

local vasoconstriction

directs blood away from poorly ventilated, hypoxic regions of the lungs

44
Q

what does systemic hypoxia cause?

A

vasodilation

45
Q

what changes occur to the pulmonary circulation during exercise?

A

pulmonary arterial pressure doesn’t change

pulmonary arterial resistance decreases

46
Q

what is the mechanism for reducing vascular resistance in the lungs?

A

pulmonary arteries and arterioles are thin walled
distend when exercise starts
stretching generates reflex relaxation of arterial smooth muscle
vessels relax and enlarge, reducing vascular resistance

47
Q

what happens to the alveoli when there’s increase PO2?

A

arterioles dilate

48
Q

why is pulmonary vascular resistance high in the foetus?

A

hypoxic vasoconstriction in the foetal lungs

49
Q

what is the foramen ovale?

A

the hole in the foetal atrial wall which shunts blood between the left and right atria

50
Q

when does the foramen ovale close?

A

shortly after birth

51
Q

what is the ductus arteriosus?

A

short tube joining the aorta and pulmonary artery

52
Q

what is the purpose of the ductus arteriosus?

A

allows some of the blood from the right ventricle to bypass the lungs and enter the aorta directly

53
Q

when does the ductus arteriosus close?

A

immediately after a baby takes their first breath

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