Blood Vessles Histology Flashcards
What are the 3 basic layer structure to blood vessels
Inner layer: tunica intima - single layer of squamous epithelial cells termed endothelial cells. Supported by basal
lamina and thin layer of connective tissue
(Layer of internal elastic membrane)
Middle layer: tunica media - predominantly made of smooth muscle, thickness varies
(Layer of external elastic membrane)
Outermost layer: tunica adventitia - supporting connective tissue
What are elastic arteries?
The very largest arteries e.g aorta.
This is because they have many sheets of elastic fibres in their tunica media to provide elastic recoil
What is the vasa varosum?
The vascular supply in large arteries so they can obtain their nutrients (only the inner part of the wall can obtain nutrient from the lumen)
What is the structure of arterioles?
One or two layers of smooth muscle in their tunic media and almost no adventitia.
Important in controlling blood flow in a tissue
What are capillaries structure and what are the 3 kinds?
Composed of endothelial cells and basal lamina
Often have pericytes at intervals just outside the basal lamina - these are connective tissue cells that have contractile properties
Continuous capillaries: more common. Found: muscle connective tissue, lung, skin, nerve
Fenestrated capillaries: have ~ 50nm pores in wall. Found: mucosa of gut, endocrine glands, glomeruli of the kidney
Sinusoidal or discontinuous capillaries: lack basal lamina, large gaps that macromolecules and sometimes cells can pass. Found: liver, spleen and bone marrow
What are microvasculature networks
Small arterioles connect to a postcapillary venule via a network made up of metarterioles, thoroughfare channels and capillaries.
Precapillary sphincters, composed of smooth muscle, at the beginning of the capillary to help control flow through network
Capillary venules drain into post-capillary venules. How do you know when they become venules?
Post capillary venules are endothelial cell-lined and contain a thin layer of connective tissue and ocasional pericytes (important sites of exchange)
Once vessel acquires intermittent smooth muscle cells in tunica media layer, they are venules
What do most small-medium veins have?
Valves - they are inward extensions of the tunica intima
What is the structure of veins?
Relatively thin tunica intima and media. Tunica media consisting of a few layers of smooth muscle (smaller than arteries TM)
The largest veins (e.g. vena cava or hepatic portal vein) have a thick tunica adventitia with lots of bundles of longitudinally oriented SM
Veins are flexible so contain most of the blood in the body
