Systemic Circulation Flashcards
Vessels are primarily composed of which four things?
- endothelial cells
- elastin
- vascular smooth muscle
- collagen
How is compliance determined?
change in volume / change in pressure (looks at how pressure changes in relation to a given change in volume)
Does a less compliant (more stiff) vessel have a larger or smaller pulse pressure?
A stiffer vessel has a larger pulse pressure
What are the primary differences in composition between an artery and a vein?
- arteries have elastic lamina
- arteries have more VSM
- arteries have less connective tissue (adventitia)
Rank the compliance properties of the arterial wall components (collagen vs. elastic lamina vs. smooth muscle)
in order of decreasing compliance…
elastic lamina > VSM > collagen
What are the implications of veins lacking an elastic layer?
Because of this, veins act as passive bags and can fill with blood but cannot squeeze back down as effectively as arteries.
In which layer are the vasa vasorum found?
in the tunica adventitia
Where is the most common place to find a continuous capillary?
in connective tissues
Where are fenestrated capillaries most commonly found?
in the kidneys and intestines
Where are discontinuous (sinusoidal) capillaries most commonly found?
in the liver, bone marrow, and spleen - all allow a lot of things to enter/leave via wide spaces in capillaries
The higher the ___________ ratio, the greater the control of vessel diameter and blood flow.
wall thickness to lumen diameter
Which vessels have the highest wall thickness to lumen diameter ratio and what is the implication?
arteriole and pre-capillary sphincters; this means they have the greatest control over vessel diameter and blood flow
How much of our blood volume is sitting in our veins, on average?
~64%
If capillaries have the largest total CSA, why do they have such a small blood volume?
This is because they are so short and physically cannot hold a lot of blood volume.
Why does the aorta have such a small blood volume?
Blood is never held in the aorta, as it is rapidly being pumped out through the systemic circulation to other areas of the body.
Which vessels have the lowest total resistance and why?
capillaries because they have the largest total cross sectional area
Where does the largest drop in arterial pressure occur?
in the resistance vessels, primarily the arterioles (we use up most of the pressure generated by the LV to get blood through the resistance vessels)
What does pulse pressure represent?
the force of contraction of the heart (difference b/t systolic and diastolic pressures)
The average pressure existing in the aorta and proximal arterial system during one cardiac cycle.
Mean Arterial Pressure (MAP)
Is MAP determined more by systolic or diastolic pressure?
diastolic
Is there a pulse pressure in the capillaries and veins?
no!
Why does pulse pressure widen in vessels farther from the heart?
decrease in compliance, as well as Bernoulli’s principle (decreased velocity=increased pressure)
Why does a patient with an LVAD not have a pulse?
The device is continuously circulating blood around the body, so there is no need for pulsatility to pump the blood through the circulation.
Explain the hydraulic filtering of the aorta and how this relates to its compliance.
-The volume ejected from the LV during systole is temporarily stored by distention of the elastic component of the aorta (compliant vessel); after systole ends, the distended aortic wall recoils and acts as a secondary (Windkessel) pump to maintain constant flow during diastole
How does the aorta remodel itself with aging?
compliance decreases due to less elastin and more collagen
What happens with a less compliant aorta in terms of work?
A stiffer aorta has to do more cardiac work to pump a sufficient volume of blood; more work=greater O2 consumption=larger energy requirements
Are arteries more or less compliant than veins?
less compliant; this is why arteries are resistance vessels and veins are capacitance vessels
How are pulse pressure and pressure pulse related?
a larger pulse pressure corresponds to a faster pressure pulse
How does the velocity of propagation of the pressure pulse change with compliance?
decreased compliance (stiffer vessel) corresponds to an increased velocity of propagation
