Special Circulations Flashcards
Features of Pulmonary Ciculation
Low Pressure
Low resistance
What is the optimal ventilation perfusion ratio
0.8
What can help ensure optimal ventilation- perfusion ratio?
Hypoxic pulmonary constriction
Alveolar hypoxia results in vasoconstriction of pulmonary vessels.
Consequence of chronic hypoxic vasoconstriction
Right ventricular failure
Effect of exercise on pulmonary blood flow
Increased cardiac output
Small increase in arterial pressure
Opens apical capillaries which are normally closed during diastole
Increased oxygen uptake by lungs
As blood flow increases capillary transit times is reduced.
Why dies the brain need a high oxygen demand
Neurones are always active
How does the cerebral circulation meet the high demand for oxygen
High capillary density
High basal flow rate
High oxygen extraction
What is hypercapnia and what occurs because of it
Increase in the partial pressure of carbon dioxide and it cause vasodilation
How does the coronary circulation meet high demands of oxygen
High capillary density
Short diffusion distance
Continuous production of nitrous oxide maintains high basal flow
What complications can occur in the coronary circulation
Prone to atheromas
Narrowing of coronary arteries leads to angina when exercising
Thrombus obstruction can cause MI
Features of the skeletal muscle circulation
High vascular tone permits lots of dilation
At rest about a half of capillaries are perfused which allows increased recruitment
Variety of muscles have different capillary densities
Problems associated with skeletal muscle circulation
Atheroma formation
Intermittent claudication
What is regulated by the cutaneous circulation
Heat release from skin
What specialised structures are present in the apical skin
Artereovenous anastomoses (AVAs)
How to AVAs regulate heat loss
Decrease in temp causes an increase in sympathetic tone in AVAs. This decreases blood flow to apical skin.
Increase in temp causes a reduced vasomotor drive to allow AVAs to dilate which diverts blood to surface on skin.
