Properties of Vasculature Flashcards
What are the three layers of the large blood vessels?
Intima - innermost, single layer of thin endothelium
Media - smooth muscle in a matrix of collagen, elastin, and glycoproteins
Adventitia -outermost, collagen, fibroblasts, blood vessels and autonomic nerves
What are capillaries composed of?
Endothelial cells and a basal lamina
no smooth muscle
What is the function of the aorta?
Distributes blood from the heart
Dampens the pulatile pressure that results from the intermittent ejection of blood
What vessels are the primary resistance vessels that regulate arterial blood pressure?
Arterioles
Describe capillaries
Smallest vessels
Have the greatest cross sectional area
Responsible for nutrient exchange
What are the primary capacitance vessels of the body?
Venules and Veins
Most of the blood volume is here and this is where regional blood volume is regulated
Describe the pressure of the systemic circuit
The mean BP is highest in the aorta and progressively decreases as the blood flows further away from the heart
Largest pressure drop is across the arterioles
What is the relationship between blood flow velocity and area?
Velocity is inversely proportional to the cross sectional area of the blood vessel
What two factors determine blood flow through a vessel?
Pressure difference at the two ends
Resistance of the vessel to flow
What factors determine the resistance to blood flow within a vessel?
Length
Vlood viscosity
Radius of the vessel
What is Poiseuille’s equation?
Describes blood flow within a vessel
The rate of blood flow is directly proportional to the fourth power of the radius of the vessel
What is the major mechanism for changing blood flow in the CV system?
Changing the resistance of blood vessels, particularly the arterioles
What is the effect of pressure on tissue blood flow?
And increase in arterial pressure increases blood flow through various tissues of the body
Increases the force that pushes blood but also distends the vessels at the same time, decreasing vascular resistance
How does sympathetic stimulation affect blood flow?
Inhibition of sympathetic activity greatly dilates vessels and increases blood flow
Stimulation can constrict the vessels so that blood flow decreases
What is the relationship between blood flow and blood viscosity?
The greater the viscosity, the less flow
Viscosity increases as hematocrit increases
What is laminar flow?
Blood normally flows through all vessels in the CV system in an orderly streamlined manner
What is turbulent flow?
The fluid moves irregularly in axial, radial, adn circumferential directions
What conditions cause turbulent blood flow?
When the rate of blood flow becomes too great
When is passes by an obstruction in a vessel
Sharp turns
Passes over a rough surface
What is reynolds number?
Way to predict turbulent blood flow
Re > 2000 - turbulent flow
Describe resistance when blood vessels are arranged in series
The total resistance is equal to the sum of the resistance of each vessel
The total flow through each vessel of the system is the same
Describe resistance when blood vessels are arranged in parallel
The reciprocal of the total resistance is equal to the sum of the reciprocals of the individual resistances
Parallel vessels greatly reduce resistance
Capillaries have the highest resistance as individual vessels, but because of their arrangement their resistance is reduced
What is vascular compliance?
How much volume changes in response to a given change in distending pressure
The compliance of the venous system is much greater than that of the arteriole system
What is the significance of the distensible nature of the arteries?
It reduces the pressure pulsations to almost none by the time blood reaches the capillaries, allowing mainly continuous blood flow
If not for this, then all blood flow would have to occur during systole
What is the pulse pressure?
The difference between systolic and diastolic pressures
