Vessels of the systemic circulation Flashcards
How are vessels categorized?
Based on size:
Microvessels
Macrovessels
Why are arteries and arterioles considered to be the primary resistance vessels?
They have the most smooth muscle which contract or dilate to regulate blood flow
What is the advantage to capillaries only being one cell thick?
Aide in exchange of diffuse substances
How does the velocity of the blood increase as it returns to the heart?
The number of veins to capillaries is decreased (decrease CSA) which causes velocity to increase
What two factors determine the CVP?
Venous return
Pumping ability of the right side of the heart
How does blood make it back to the right side of the heart?
Venous blood only flows to the right atrium because of a favorable pressure gradient (venous pressure must be greater than right atrial pressure)
What three factors cause and increase in venous return?
Increased blood volume
Increase large venous vessel tone
Dilation of arterioles (more blood moves to venous side)
When can an increase in venous resistance occur?
Compression of vessels
Sharp angulations
How can standing stationary for long periods of time cause edema in the lower extremities?
Since muscles are not moving and actively squeezing the blood back to the heart, the pressure in the veins builds up (up to 90mmHg) causing fluid collection and edema
How does the valsalva maneuver effect venous return?
Generates a very large intrathoracic pressure that is transmitted to the vessels this increases resistance and generates a back pressure that will decrease venous return to the heart
Why doesn’t forced expiration have equal effects as forced inspiration?
Forced inspiration causes sucking of blood back to the right atria from the negative intrathoracic pressure causing a large increase in blood return, forced expiration causes veins to collapse from positive intrathoracic pressure causing blood return to decrease but only by a little because we have valves that prevent the back flow of blood
Why are patients at risk for vfib taught to cough rhythmically?
It is supposed to help maintain cerebral blood flow and consciousness
What type of vessels determines the amount of blood flow for a given pressure?
The diameter of arterioles determines how much blood flow there will be for a given pressure
Why do some people experience lightheadedness after a coughing fit?
Intrathoracic pressure is increased, narrowing or collapsing some of the vessels returning blood to the heart which causes resistance and generates a back pressure
