Learning Objectives
•At the end of the session, the students should be able to:
•Enlist the functions of veins
•Explain venous pump
•Explain venous pressures and their role in resistance to blood flow
•Discuss the effect of gravity on veins
•Explain venous return and factors affecting it
Content of activities
•Discussion in the form of assignment
•Presentation of each assignment
Assignment Discussion (20 mins)
•Enlist the functions of veins
•Explain venous pump
•Discuss the effect of gravity on veins
•Explain venous return and factors affecting it
Presentation (15 mins)
•Enlist the functions of veins
•Explain venous pump
•Discuss the effect of gravity on veins
•Explain venous return and factors affecting it
Enlist the functions of veins
Functions of veins
•Passageway for flow of blood
•Can constrict and dilate
•Storage site for blood
•Very compliant
•Venous pumps
•Regulate cardiac output
•Maintains homeostasis
•Venuloarteriolar signaling
Compliance
•Increase in volume per unit increase in pressure
•It is the measure of how easily a vessel can be stretched and accumulates fluid
•Veins are much more compliant than arteries
•Compliance = dispensibilityx volume
Discuss the effect of gravity on veins
Venous Pressures
The pressure resulting from the weight of the water on the surface is called gravitational pressure or hydrostatic pressure.
Explain venous pump
•There are valves in the veins
•Arranged so that the direction of venous blood flow can be only toward the heart
•Consequently, every time a person moves the legs or even tenses the leg muscles, a certain amount of venous blood is propelled toward the heart.
•This pumping system is known as the “venous pump” or “muscle pump,”
What will happen if we stand perfectly still?
•The venous pump will not work
•Venous pressures are going to increase
•Fluid can leak from the capillaries
•Causing leg swelling
What are the storage sites of blood?
•Veins contain around 60% of total blood
•(1) the spleen
•(2) the liver
•(3) the large abdominal veins
•(4) the venous plexus beneath the skin
•The heart and the lungs, although not parts of the systemic venous reservoir system, may also be considered blood reservoirs.
Explain venous return and factors affecting it
Venous Return
The volume of blood entering each atrium per minute from the veins.
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