Vascuar Histology Flashcards
What are the three layers of the tunica intima
Endothelium
Basal lamina
Subendothelial layer
What makes up the endothelial layer of the tunica intima
A single layer of squamous epithelial cells with a basal lamina containing a thin EC layer
What makes up the subendothelial layer and what makes up the internal elastic membrane
Loose CT with an internal elastic membrane Which is made up of fenestrated elastic material
What is the purpose of the subendothelial layer
To link the endothelial layers to the other ones
What is the purpose of the internal elastic membrane
Allows for nutrients to diffuse across the tunica
What makes up the smooth muscle
Smooth muscle with a layer of elastin that comprises the external elastic membrane
Describe the tunica adventitia
Longitudinally arranged collagenous tissue w/few elastic fibers.
Merges with the loose CT surrounding the vessels
Define the vasa vasorum
Supplies blood to the vascular walls themselves
This is how the larger vessels get their nutrients
Define the nervi vasorum
ANS input that controls contraction of vascular smooth muscle
The vasa vasrum and nervi vasorum are part of that tunica
Tunica adventitia
What are the defining characteristics of large (elastic) arteries
Elastin which forms concentric sheets between muscle cell layers
No fibroblasts
What synthesizes collagen, elastin, and ECM in large arteries
Smooth muscle
Medium (muscular) arteries have more what and less what in compared to larger arteries
More SM and less elastin
What becomes readily aparent in the medium arteries
Internal elastic membrane and the external elastic membrane
Is the tunica adventitia thick or thin in medium arteries
Thick
How many layers do small arteries have or tunica media smooth muscles
Up to 8 with an internal elastic membrane
How many layers of smooth muscle in the tunica media will the arterioles have
1 - 2 layers
What are the duties of the arterioles
Flow regulators for the peripheral capillary beds through sympathetic (vasoconstriction) or parasympathetic (vasodilation) innervation
Innervation is in the tunica media
Capillaries only have what type of layering
Endothelium with tunica intima
What surround the capillary beds and what is their role
Pericytes - enclosed within the basal lamina that is continuous with the endothelium
Promotes stability of capillaries and post-capillary venules
What are the first branches of the arteriole supply the tissue
Metarterioles
What is the thoroughfare channel and what does it lack
Distal end of metarteriole
Lacks SM
Define true capillaries
Branch from metarteriole and lack SM
Contracted precapillary sphincters will cause what
A shunt of blood to flow through the capillaries, causing faster VR and less exchange within true capillaries
The lumen of arteries or veins is bigger
Veins
What doe postcapillary venules do and what do they not contain
Drain capillaries
No true tunica media
What is the first vein to have all three layers of tunica
Small veins
Tunica media have thicker what
Adventitia
Muscular venules have what in regards to smooth muscle and tunica adevntitia
1-2 layers of SM in tunica media and a thin tunica adventitia
What is the thickest layer of the large veins
The tunica adventitia
What does the tunica adventitia of large veins contain
Collagen and elastic fibers AND fibroblasts
Where is the smooth muscle found in large veins
Tunica adventitia
Which type of vein contains valves
Medium veins
