Histology - Blood and Blood Vessels Flashcards
(85 cards)
3 layers of blood vessles
Tunica intima, tunica media and tunica adventitia
Tunica intima
Single layer, squamous epithelium with a basal lamina and and a thin connective tissue layer
Tunica Media
Mostly smooth muscle, varying level of tissue thickness
Tunica Adventitia
Supporting connective tissue
Separation of tunica intima and tunica media
Internal elastic membrane - layer of elastic tissue
Separation of tunica media and tunica adventitia
External elastic membrane - layer of elastic tissue
Staining elastic fibres
Not using common stains eg H&E but special ones (not named)
Variation in blood vessel structure
In large arteries (eg Aorta) a significant amount of smooth muscle in tunica media is replaced by sheets of elastic fibres - elastic arteries
What is the purpose of ‘Elastic Arteries’
To provide elastic recoil
Vascular supply in elastic arteries
They have their own vascular supply - ‘vaso vasorum’ as only the inner part of the wall can get nutrients from the lumen
Tissue layers in Arterioles
Only one or two layers of smooth muscle in tunica media and miniscule amounts of adventitia
How are arterioles formed?
Arteries become smaller losing smooth muscle from tunica media. (they are around 30-200µm)
Why are arterioles important?
Help to control blood flow in tissues
Capillaries
Composed of endothelial cells and a basal lamina and have diameters of 4-8µm, they also form networks
3 types of capillaries
Continuous, fenestrated and discontinuous/sinusoidal
Continuous capillaries
An uninterrupted lining which only allows small molecules (eg water to pass)
Location of continuous capillaries
Muscle, nerve, lung, skin
Fenestrated capillaries
Have small pores (50nm) to allow extensive molecular exchange. more permeable than continuous
Location of fenestrated capillaries
Gut mucosa, endocrine glands, kidney
Discontinuous capillaries
Have much larger gaps (remember also sinusoids)
Location of discontinuous capillaries
Liver, spleen, bone marrow and lymph nodes
Microvasculature
(Basically) a small arteriole connected to a postcapillary venule through a network of metarterioles, thoroughfare channels and capillaries.
What is a metarteriole?
A short microvessel that links arterioles and capillaries. No continuous tunica media instead spaced smooth muscle that forms a precapillary sphincter.
What is a thoroughfare channel?
Links metarterioles to venules. Form arteriovenous anastomoses