overview of CVS function Flashcards
CVS is a bulk flow system involved in the delivery of:
- O2 and CO2
– Nutrients
– Metabolites
– Hormones
– Heat
Explain Darcy’s law:
flow through any vessel is proportional to the pressure difference and inversely proportional to the resistance in the vessel
flow = Δpressure/ resistance
how do you calculate the pressure difference?
Mean Arterial Pressure (high) - Central Venous Pressure (low)
Affects all tissues.
what is the resistance of a vessel controlled by?
radius4, the relation between them is inversely proportional.
Selectively redirects flow.
what is the role of arterioles?
they act as “the taps”, controlling resistance (and therefore flow) to each vascular bed
where is the highest and lowest pressure found?
high: aorta and systemic arteries as they receive blood from the left ventricle.
low: vena cava just before they empty into the right atrium
describe the venous capacitance:
the ability of the venules and veins to store blood.
Can store up to 2/3 of blood volume → controls the fractional distribution of blood
describe poiseuilles law (resistance):
(1) resistance to fluid flow offered by a tube: increases as the length of the tube increases
(2) resistance increases as the viscosity of the fluid increases
(3) resistance decreases as the tube’s radius increases.
explain what the fractional distribution of blood is:
what proportion of total blood is in veins & venules (capacitors) and what proportion is in the rest of the circulation
define the aorta:
an elastic artery with the widest lumen (low resistance)
Elasticity allows damping down pressure, reducing pressure during contraction and maintaining pressure during relaxation
define the muscular arteries:
wide lumen
strong
non-elastic walls
low resistance
define the arterioles:
vessels that have a narrow lumen, with a thick contractile wall.
Controls resistance & flow → through constriction and dilation
This allows regional redirection of blood
define capillaries:
they are exchange vessels with the narrowest lumen, and very thin walls.
this gives them a large surface area to volume ratio
-> allows diffusion of oxygen with tissues.
define veins and venules:
they are capacitance vessels with a wide lumen.
Have low resistance and acts as a blood reservoir.
This allows fractional distribution of blood.
state the function of papillary muscles:
they are attached to chordae tendinae which prevent the tricuspid and mitral valves from inverting and opening the other way during contraction.
This prevents regurgitation of blood, which is very bad!
