Vascular Histology Flashcards
3 layers of a blood vessel wall, from the inside out?
Intima
Media
Adventitia
As the diameter of arteries decreases, does the relative thickness of the vessel wall increase or decrease?
Relative thickness increases.
What’s in the tunica media?
Smooth muscle, collagen, elastic fibers.
In what layer are vasa vasorum and nerve bundles?
The adventitia.
Which layer varies the most between arteries and veins?
The media
What are 3 variants of capillaries with differing permeabilities?
Continuous (least permeable) -
Fenestrated - kidneys
Discontinuous (most permeable, allows cells through) - spleen, liver, lymph nodes
Are arteries or veins better at accomodating changes in volume?
Veins are better
What’s one reason why a vein’s valves might not work?
Veins are too distended, so valves can’t close.
Which vessels most regulate blood pressure?
Small arteries and arterioles.
2 endothelial-derived signaling molecules that induce vessel relaxation?
NO
Prostacyclin
1 endothelial-derived factor that induces blood vessel constriction?
Endothelin-1
What are “dense bodies” on smooth muscle cells? To what are they connected?
They’re anchoring sites for actin in the contractile elements. They connect to intermediate filaments (desmin and vimentin).
How do the myosin “thick filaments” differ in smooth muscle vs. skeletal muscle? What effect does this have?
In smooth muscle, all heads on one side pull one direction, and there are heads staggered throughout the length of the thick filament. - This is called “side polarity.”
The contractile elements can keep pulling with consistent strength over a longer distance vs. skeletal muscles’ sarcomeres.
What is the role of myosin regulatory light chain (RLC, or rMLC) in smooth muscle?
It controls whether myosin can bind ATP.
How is RLC (aka rMLC) regulated? (Enzymes that do this?)
By phosphorylation:
Phosphorylated - RLC allows ATP to bind myosin - MLC Kinase
Dephosphorylase - RLC prevents ATP binding to myosin - MLC phosphatase.
