Tunica media (myocardium) is the largest
of the three layers, and contains cardiac
muscle fibres, and loose endomysial connective tissue that
contains lots of capillaries.
Tunica Intima (endocardium) of the heart- stratified squamous epithelium.
Tunica adventitia - has small 'vasa vasorum'
- - as the large arteries need their own blood supply.
Tunica media - broad, elastic - concentric fenestrated
sheets of elastin, and collagen, few muscle fibres.
Tunica intima - single layer of flattened epithelial cells,
supporting layer of elastin rich collagen. Has 'myointimal
cells' that accumulate lipid with ageing - first sign of
Tunica intima - flattened endothelial cells
Tunica media: - muscle layer, (with some elastin and collagen),
sandwiched by an Internal Elastic Layer (IEL), and an External
Elastic Layer (EEL).
Notice how the tunica media layer is relatively
smaller than that for the elastic artery.
Tunica Adventitia - very broad, mostly collagen and elastin.
Tunica intima - single layer of squamous epithelium.
Tunica media - few or single layer of smooth
Tunica adventitia - much reduced, merges in
with surrounding tissue.
This shows a vasa vasorum. The large lumen suggests
that it is a venule. It consists of a single layer of flattened
endothelial cells. There is no tunica media or
tunica adventitia layer.
Tunica adventitia layer is the most prominent layer, and has collagen fibres.
Tunica Media is the most prominent layer.
There is no inner or outer elastic layer, as in a Muscular Artery.
Some questions for you to think about:
How do the structures of muscular arteries and veins differ?
Muscular arteries and veins both regulate their diameters by
contraction of the muscle layers in the tunica media, yet this
layer appears very different in the two types of vessel.How do
you explain this?
How does the structure of the tunica adventitia differ from that
of the muscular artery?
The lumen of the artery on this slide is very regular but that
of the vein is very irregular. How is this difference related
to the structure of their walls?