8. Special Circulations Flashcards
The metabolic needs of the lungs are met by which circulation?
Bronchial circulation
What is the optimal ventilation perfusion ratio?
0.8
Alveolar hypoxia leads to what happening to the pulmonary vessels and why is this beneficial?
Vasoconstriction, this allows optimal gas exchange as less well ventilated alveoli are less well perfused
Chronic hypoxic vasoconstriction can be caused by what?
Altitude
Emphysema
Chronic hypoxic vasoconstriction can cause what condition?
Right ventricular failiure
Why is pulmonary oedema unlikely to occur normally?
Pulmonary capillary pressure is low hence hydrostatic is small relative to oncotic pressure so little fluid leaves
What can increase pulmonary pressure?
If left atrial pressure rises due to:
Mitral valve stenosis
Left ventricle failiure
What is the affect of exercise on pulmonary blood flow?
Increased cardiac output
Vasodilatation of pulmonary system
More O2 exchange
System stable as demand met
What is Cushing’s reflex?
Where impaired blood flow to the brain is dealt with by increasing sympathetic vasomotor activity increasing arterial blood pressure to maintain cerebral flow
The filling of the coronary circulation occurs mostly during which part of the cardiac cycle and why?
Diastole
Pressure decreases due to heart relaxation
Coronary endothelia produce which chemical to cause vasodilation to ensure blood flow?
NO
Increasing core temperature causes what to happen in cutaneous circulation to dissipate heat?
Artereovenous anastamoses open
Increased blood flow to skin
Heat dissipated via shunting to venous plexus
The pulmonary circulation is supply driven, what does this mean?
Must accommodate all of cardiac output
