Pulmonary and bronchial circulation Flashcards
Flash cards comprise Kam power/Deranged physiology and Wests. Only the first 3 pages of Nunns chapter included
Mean pulmonary artery pressure? Pulmonary trunk diametre?
15mmHg or 20cmH20 (25/10) = 1/6 of mean systemic arterial pressure
30mm
Mean pulmonary arteriole pressure
12
Mean pulmonary vein pressure
8
RV pressure
25/0
RA pressure
2
LV pressure
120/0
LA pressure
5
Mean systemic arterial pressure
100 120/80
Mean systemic veinous pressure
5-10
Mean systemic arteriole pressure
30
Mean systemic capillary pressure
20
Mean systemic venule pressure
10
Why is there a more pronounced pressure drop in the systemic circululation than in the pulmonary circulation?
- Muscular arteriole mediated blood flow regulation at entrance to organs leading to profound pressure drop across capillary system in systemic circulation
- Pulmonary artery shorter, thinner walled more distensible than the aorta ith less smooth muscle
Define vascular resistance
Flow = pressure / resistance
Resistance = flow/pressure
How are the pulmonary and systemic arterial systems different? Show this mathematiucally?
Identical flow
Pressure drop across pulmonary circulation (mean values) 15 - 5 = 10mmHg
In systemic circulation drop is 100-5 = 95mmHg
Therefore MUCH higher systemic vascular resistance
What pressures are the capillaries exposed to in the pulmonary system?
- Alveolar pressure - if alveolar pressure is higher than capillary pressure then the capillaries collapse
What is the difference in thw walls of the BV system between the pulmonary and systemic?
Pulmonary blood vessels markedly thinner
How to tell the difference on a microscope between a vein and an artery in the lung?
Veins are not accompanied by airways, whereas arteries are accompanied by arteries especially more distally; arteries and airways travel down the centre of lobules whereas veins travel down the peripheries of lobules
There is however not much difference in their thickness, but generaly veins are fewer in numbre, thinner walls, less muscular, less elastic and more collagenous. Interestingly pulmonary veins drain seamlessley into the LA with no fold/border. At their largest half the width of pulmonary arteries
How is the path different between a vein and an artery in the lung?
Veins are not accompanied by airways, whereas arteries are accompanied by arteries
There is however not much difference in their thickness
How is the pressure different between arteries/veins and capillaries in the lung?
Alveolar capillaries - these are compressed between alveoli by alveolar pressure
Pulmonary vein and arteries - extra-alveolar vessels therefore the alveoli/lung parenchyma pull on the veins and arteries as they expand
Alveolar vs extra-alveolar vessels? Whats the difference? How do their calibres change with inspiration and expiration?
Inspiration/expansion of lung volume - increased alveolar resistance, however reduced pulmonary vein/artery resistance
The inverse with expiration
What is the resistance equation
Resisatnce = input pressure - output pressure/flow
What is the difference between vascular and electrical resistance?
Resistance does not change depending on upstream and downstream pressure in electrical systems; HOWEVER physiologically the pressure changes do change the resistance in the lung
Draw a diagram equating pulmonary vascular resistance with arterial or veinous pressure? Give units? Why does this relationship occur? (2) HOw elastic is the pulmonary capillary?
Now draw another diagram describing the relationship between PVR and lung volume? Explain the trends? Explain the different effects on vessels in different areas that explain this? Where is the normal scope of breathing on these diagrams?
- Recruitment of capillaries with increasing flow
- Distension of existing capillaries with increasing flow reducing their resistance
Baseline flow is not enough to distend to maximal diametre as partial collapse; highly elastic thinner walled vessels with less muscle