pulmonary circulation

Question 1

what are the 2 circulations in the lung?

Answer 1

pulmonary and bronchial

Question 2

what circulation is the bronchial circulation part of?

Answer 2

systemic circulation

Question 3

what does the bronchial circulation supply?

Answer 3

capillary beds in the trachea and bronchi smooth muscle

Question 4

where do bronchial arteries branch off from?

Answer 4

early parts of the descending aorta

Question 5

where does the bronchial venous drainage drain into?

Answer 5

bronchial veins in the right atrium

pulmonary veins going into the left atrium

Question 6

where are the bronchial arteries found?

Answer 6

travelling along the main bronchi

Question 7

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

Answer 7

5 seconds

Question 8

what is the surface area of the lungs?

Answer 8

50-100m2

Question 9

what are the special anatomical features of the pulmonary circulation?

Answer 9

thin walled pulmonary arteries
large diameter
highly distensible

Question 10

what letter represents blood flow?

Answer 10

Q

Question 11

give an equation to calculate blood flow

Answer 11

pressure gradient/resistance

Question 12

which has lower pressure; the pulmonary or systemic circulation?

Answer 12

pulmonary

Question 13

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

Answer 13

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

Question 14

what happens if pulmonary arterial resistance rises?

Answer 14

pulmonary arterial hypertension

right heart enlarges and eventually fails

Question 15

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

Answer 15

somatic nerve supply

to T2-T6

Question 16

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

Answer 16

T2 to T4-6

Question 17

which part of the lungs do the sympathetic nerves innervate?

Answer 17

smooth muscle in the bronchial walls and small pulmonary vessels

Question 18

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

Answer 18

bronchodilation and vasodilation

Question 19

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

Answer 19

adrenergic beta receptors

noradrenaline

Question 20

what nerve delivers parasympathetic innervation to the lungs?

Answer 20

the vagus

Question 21

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

Answer 21

bronchoconstriction

stimulates secretion of mucus in the bronchi

Question 22

where does gas exchange in the lungs occur?

Answer 22

alveolar ducts and alveoli

and to the respiratory bronchioles to a small extent

Question 23

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

Answer 23

the base

Question 24

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

Answer 24

gravity helps blood circulate because pulmonary blood pressure is low

Question 25

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

Answer 25

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

Question 26

when is total cessation of flow in the apices seen?

Answer 26

when a person is ventilated with positive pressure or haemorrhage

Question 27

where is zone 2 of the lungs?

Answer 27

3cm above the heart

Question 28

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

Answer 28

pulsatile flow; Pa > PA > Pv flow fluctuates during inspiration and expiration bc of changes in alveolar pressure flow greater in systole than diastole

Question 29

what part of the lungs is zone 3?

Answer 29

the base

Question 30

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

Answer 30

continuous blood flow because the arterial and venous pressure always exceed alveolar pressure Pa > Pv > PA

Question 31

what is radioactive xenon used for and how?

Answer 31

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

Question 32

what letter represents lung compliance?

Answer 32

C

Question 33

what is lung compliance?

Answer 33

measure of stretchability of the lungs

Question 34

how is lung compliance measured?

Answer 34

the change in volume per unit pressure change C = dV/dP

Question 35

when is the work of breathing lowest?

Answer 35

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

Question 36

which part of the lungs has the highest compliance?

Answer 36

the base

Question 37

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

Answer 37

Q

Question 38

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

Answer 38

V

Question 39

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

Answer 39

apex - high PO2 and low PCO2 bc good gas exchange but little blood flow base - low PO2 and high PaCO2 bc little ventilation

Question 40

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

Answer 40

lower than normal

Question 41

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

Answer 41

higher than normal

Question 42

give an example of a blood flow obstruction

Answer 42

embolism

Question 43

what does pulmonary hypoxia cause and how does this help?

Answer 43

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

Question 44

what does systemic hypoxia cause?

Answer 44

vasodilation

Question 45

what changes occur to the pulmonary circulation during exercise?

Answer 45

pulmonary arterial pressure doesn't change | pulmonary arterial resistance decreases

Question 46

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

Answer 46

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

Question 47

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

Answer 47

arterioles dilate

Question 48

why is pulmonary vascular resistance high in the foetus?

Answer 48

hypoxic vasoconstriction in the foetal lungs

Question 49

what is the foramen ovale?

Answer 49

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

Question 50

when does the foramen ovale close?

Answer 50

shortly after birth

Question 51

what is the ductus arteriosus?

Answer 51

short tube joining the aorta and pulmonary artery

Question 52

what is the purpose of the ductus arteriosus?

Answer 52

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

Question 53

when does the ductus arteriosus close?

Answer 53

immediately after a baby takes their first breath