CVS 8 Special Circulations Flashcards
2 circulations of the lungs
Bronchial circulation - meets the metabolic requirements of the lungs
Pulmonary circulation - required for gas exchange
Cardiac output at rest
5L/min
Maximum cardiac output
20-25L/min
Pressure in right atria
0-8mmHg
Pressure in left atria
1-10mmHg
Pressure in right ventricle
15-30mmHg - systole
0-8mmHg- diastole - same as RA
Pressure in left ventricle
100-140mmHg - systole
1-10mmHg - diastole - same as LV
Compare and contrast the features of pulmonary and systemic circulation
pulmonary circulation:
- lower pressure + resistance
- short, wide vessels
- many capillaries
- arterioles have little smooth muscle
systemic circulation
- higher pressure + resistance
- larger, narrower vessels
- variable blood flow to capillaries
- arterioles have thick walls
Adaptations to promote efficient gas exchange
High density of capillaries - large surface area
Short diffusion distance
What is hypoxic pulmonary vasoconstriction?
Occurs when alveoli are not well ventilated
Vasoconstriction of pulmonary vessels
Ensures perfusion matches ventilation
Helps optimise gas exchange
Consequence of chronic hypoxic vasoconstriction
Increases resistance > hypertension
Outline when the vessels of the lungs are open/closed
- apical vessels - collapse during diastole
- vessels at the level of the heart - constantly open
- vessels at base of lungs - increased hydrostatic pressure > vessels distended
Effect of exercise on pulmonary blood flow in lungs
- apical vessels - open due to increase pressure
- vessel at level of heart - constantly open
- vessels at base of lungs - increased hydrostatic pressure > vessels distended
Outline the formation of tissue fluid
- hydrostatic pressure pushes fluid out of capillary
- oncotic pressure draws fluid into capillary
How does the cerebral circulation meet the high demand for oxygen?
High capillary density > large surface area
High basal flow rate
Reduced diffusion distance
High O2 extraction
