CV system Flashcards
Blood vessels
What is the tunica intima?
This layer lines the lumen (inner layer)- thin layer of endothelium (squamous epithelial).
What is the function of the tunica intima?
The cells fit closely together forming a slick surface to decrease friction as blood flows through the vessel.
What is the tunica media?
Bulky middle layer made up of smooth muscle and elastic fibres (larger arteries have sheets of elastic tissue).
What is the function of the tunica media?
The smooth muscle (controlled by sympathetic nervous system) responsible for changing diameter of the vessel (vasodilation and constriction).
What is the tunica externa?
This is the outer most tunic. Composed of fibrous connective tissue.
What is the function of tunica externa?
To support and protect the vessels.
Why is the tunica externa heavier in arteries?
Carrying blood away from the heart so must be able to expand as blood is forced into them and recoil once blood leaves.
Why does muscular pump (skeletal muscle activity) enhance venous return?
As muscles around the vein contract, this squeezes the blood towards the heart.
What is microcirculation?
This is the flow of blood from an arteriole to a venule through a capillary bed.
What are the 2 types of vessels that a capillary bed consists of?
-A vascular shunt (vessel directly connects arteriole and venule at opposite sides of bed)
-True capillaries (actual exchange vessels).
What is a pre capillary sphincter?
A cuff of smooth muscle fibres that surround root of each true capillary, acts as valve to regulate flow of blood to capillary.
