lecture 23: resp. 5

Question 1

why is pulmonary circulation a low pressure system

Answer 1

pulmonary pressure = 22/10.
this is low because the pulmonary system is a smaller circuit so it doesn’t need to be as high of pressure

Question 2

anatomical shunt in lungs

Answer 2

some venous blood from the tree returns to pulmonary aorta leading to slight deoxygenated blood contamination in left side of heart

Question 3

pulmonaru pressure profile

Answer 3

huge pressure waves between systolic and diastolic in the pul. artery, but as it reaches pumonary capillaries, pressure becomes less variable, and flow is laminar. pressure difference between arteries and left atrium so blood flows from pul. artiers to left heart

Question 4

sheet flow and vascular resistance

Answer 4

capillaries are so close that the walls fuse and a sheet forms where blood flows from arteriole side to venule side. increases contact between capillaries and alveoli

Question 5

vessel distension on vascular resistance

Answer 5

as pressure increases, some vessels become distended (swell), and this reduces resistance to flow

Question 6

vessel recruitment on vascular resistance

Answer 6

as pressure increases, some vessels are recruited by popping open and this helps decrease resistance

Question 7

why don’t you want high blood pressure in lungs

Answer 7

to prevent Oedema (prevent fluid building up in alveoli)

Question 8

chemical control of pulmonary blood vessels

Answer 8

pulmonary hypoxic vasoconstriction, where vessels aroudn an alveolus constrict because it is not having its oxygen refreshed as well and blood flow is increased to neighbouring alveoli

Question 9

reason for regional differences in blood flow in upright lung

Answer 9

• more blood supply to bottom of lung because gravity draws it down as well as pressure differences
• pressure in top of lung: alveolar > arterial > venous
• pressure in middle of lung: arterial > alveolar > venous
• pressure in bottom of lung: arterial>venous>alveolar

Question 10

why isn’t ventilation:perfusion ration 1?

Answer 10

alveolar ventilation divided by caridac output:
- ventilation is more at the base of lung than at top,

Question 11

factors controlling diffusion of gas into blood

Answer 11

1. area
2. thickness of tissue
3. partial pressure differential across tissue
4. solubility of gas in blood
5. molecular weight of gas

Question 12

pulmonary hypoxia

Answer 12

• vasoconstriction from high hypoxia
• pulmonary artery pressure rises, increase resistance and strain in right ventricle
• right heart failure

Question 13

pulmonary oedema

Answer 13

• left heart failure so congestion and pulmonary venous pressure increases.
• oedema in lungs occurs
• systemic hypoxia
• breathlessness

Question 14

blood perfusion vs diffusion

Answer 14

diffusion is the exchange of gasses whereas perfusion refers to blood flow to the alveolar tissues