Flashcards in Histology of the CVS Deck (134)
What does the tunica intima consist of in elastic arteries?
Endothelial cells with long aces, orientated parallel to the long axis of the artery.
Narrow sub-endothelium of connective tissue, with discontinuous elastic lamina
What is the main feature of the tunica media in elastic arteries?
40-70 fenestrated elastic membranes
What else does the tunica media of elastic arteries contain?
Smooth muscle cells and collagen between lamina
What is the purpose of smooth muscle cells in the elastic arteries?
Produce elastin, collagen, and matrix
How do the features of the tunica media of elastic arteries stain?
Fenestrated elastic lamallae stain black
Collagen and extracellular matrix stain turquoise
Smooth muscle stains red
What does the tunica adventitia consist of?
A thin layer of connective tissue, containing vasa vasorum, lymphatic vessels, and nerve fibres
Why are the vasa vasorum required?
Because the wall is so thick that they need their own blood supply
How does an aortic dissection arise?
If blood somehow breaks the endothelium and works its way into the tunica media, it can start getting between the elastic lamallae. The high pressure means that sections are forced apart.
What is the problem with aortic dissections?
Can be catastrophic
The collected blood is susceptible to clotting. If this continues, may rupture the aorta
When does aortal dissection happen a lot?
Marfan’s syndrome, due to the defected elastin
Where in the aorta can a dissection occur?
Anywhere along the length of the aorta
How are aortal dissections treated?
An endovascular stent is placed, which means there is no flow to the aortic dissection, and the blood can flow through the stent graft
How does the tunica intima appear in small elastic arteries?
Indistinct endothelial cells
What does the tunica media of an elastic artery have?
Elastin lamellae, smooth muscle cells and extracellular matrix
What is the tunica adventita of small elastic arteries made of?
What is the importance of the elastic walls of small elastic arteries?
They can store energy in systole, helping move blood along
What does the tunica media of muscular arteries consist of?
Endothelium, a sub endothelial layer, and a thick internal elastic lamina
What is the main feature of the tunica media of muscular arteries?
40 layers of smooth muscles, connected by gap junctions
Why are the muscle cells of the tunica media connected by gap junctions in muscular arteries?
For coordinated contraction
How are the smooth muscle layers in muscular arteries arranged?
What does the tunica adventitia consist of in muscular arteries?
A thin layer of fibroelastic connective tissue, containing vaso vasorum, lymphatic vessels and unmyelinated nerve endings
How do the vaso vasorum in muscular arteries differ in muscular arteries from those in elastic arteries?
They are not very prominent
What stimulates vasoconstriction?
Sympathetic nerve fibres
How does vasoconstriction of muscular arteries occur?
The neurotransmitter noradrenaline is released at nerve endings, and diffuses through fenestrations in the external elastic lamina into external tunica media, to depolarise some of the superficial smooth muscle cells. Depolarisation is propagated to all cells of the tunica media via gap junctions
What happens as branch and diminish in diameter?
The number of smooth muscle layers in the tunica media diminishes
What happens when smooth muscle is contracted?
The endothelial layer and nuclei stick out
What is an end artery?
The terminal artery supplying all or most of the blood to a body part, without significant collateral circulation, meaning there is no significant contribution to tissue from another artery
What do end arteries undergo?
Progressive branching, without the development of channels connecting with other arteries
What happens if an end artery is occluded?
There is insufficient blood supply to dependant tissues, so nutrient and oxygen supply is seriously compromised