Introduction to the circulatory system Flashcards
What is the purpose of the cardiovascular system?
fluid transportation system
What is being transported
Red blood cells: O2 and CO2 to and from the lungs, white blood cells and antibodies to sites of infection, nutrients to the liver to cells throughout the body, hormones for endocrine organs to target
Aorta –> arteries and arterioles
thick walled, more muscular, smaller diameter, high pressure
Vena cava –> veins
Thin walled, collapse easily, large diameter, low pressure
Macrovessels
aorta, artery, vein, vena cava, arteriole
Microcirculatio
terminal arteriole, capillary, venule, holds more than half of our blood volume
Arterial vessels and large veins
have elastic tissue, have smooth muscle, have fibrous tissue (help keep shape)
Capillaries and venules
do not have elastic tissue (do not stretch), do not have smooth muscle (do not contract), do not have fibrous tissue (collapse and close)
Small arteries (SA) and arterioles (ART) are
resistance vessels
Resistance
= deltaP/Flow –> mmHg/L/min
Conservation of Mass
Flow = velocity * area = V * A + ~5 L/min
Blood pumps
from the left ventricle into the aorta to the large artery, small artery, arteriole, capillaries, venule, vein, vena cava and then the right atria
Large arteries
fast flow with little pressure drop, high pressure conduits
Small arteries and arterioles
large pressure drop - control flow, resistance vessels
capillaries
diffusion - exchange
venules and small veins
capacitance - hold a large volume at low pressure, low pressure capacitance/volume
large veins
low resistance conduits back to the heart
Baroreceptor reflex system
controls blood pressure
Poiseuille’s law
F = P1-P2/R, flow is proportional to the pressure/voltage gradient, flow is inversely proportional to the resistance
R (resistance to flow) =
8etaL/pir^4
The only parameter we can change is
radius
The dominant contributors to flow resistance are
small vessels
Small amounts of this can have dramatic effects
arterial occlusion
Flow regulation is accomplished by
vasodilation and vasoconstriction in the arterioles
How do small arteries and arterioles control resistance
local (metabolic and myogenic, shear stress), neural/hormonal – signals
Startling’s Law of Filtration
Flux = K[(Pc - Pi) - (pic - pii)]
K = filtration coefficient
Pc = capillary pressure
Pi = interstitial pressure
pic = capillary oncotic pressure
pii = interstitial oncotic pressure
Venous compliance
C = change in volume/change in pressure
Arteries and arterioles
very stiff, if you add a little volume (delta V), you get a large change in pressure (deltaP)
Veins and venules
very compliant, if you add a lot of volume to the veins (deltaV), you only get a small change in pressure (deltaP)
Ca
«Cv
Flow is (arterioles)
constant, deltaP is largest for the arterioles
Resistance is
largest for the arterioles
R =
deltaP/flow
Flow is (veins)
constant, deltaP is tiny for the small veins and venules, resistance is negligible for the small veins
TPR (total peripheral resistance)
= Ra + Rv = deltaP/flow
Va
= Voa + CaPa
VV
= Vov + CvPv
decrease in (venous capacitance) or making veins stiffer Cv or smaller in diameter, Vov
Pv increase, preload increase, move more blood to the arteries
