histology of blood vessels Flashcards
what separates the tunica media from the tunica adventitia
external elastic membrane.
what separates the tunica intima from the tunica media
internal elastic fibre
what is the Tunica intima (inner layer):
single layer of squamous epithelial cells (endothelial cells) supported by a basal lamina and a thin layer of connective tissue
what is the Tunica media (middle layer):
made up predominately of smooth muscle, thickness varies (thickest)
what is Tunica adventitia (outer layer):
made up of supportive connective tissue
what are the largest arteries called and example
elastic artery
eg. aorta
what is the Vasa vasorum:
Network of small blood vessels which supply nutrients to the inner walls of larger blood vessels
describe arterioles
Only have 1-2 layers of smooth muscle in their tunica media and almost no adventitia
- important in controlling blood flow in a tissue
what are Meta arterioles:
when smooth muscle are replaced by dis-continous non-contractile cells called pericytes
what are Capillaries composed of
endothelial cells and a basal lamina
what are pericytes
connective tissue cells that have contractile properties
what are capillaries absent in
- epithelial cells resting on basement membrane
- epidermis of skin
- hair and nails
- cornea of eye
- hyaline cartilage
Continuous capillaries
are the more common and endothelial cells provide an uninterrupted lining
Found: muscle, connective tissue, lung, skin, nerve.
Fenestrated capillaries
have ~50nm pores in wall
Found: in mucosa of the gut, endocrine glands, glomeruli of the kidney
Sinusoidal/discontinuous capillaries:
have large gaps through which macromolecules (sometimes even cells) can pass, basal lamina is discontinuous or absent
Found: in liver, spleen, bone marrow
what are post capillaries important for
they are important sites for gas exchange
what do veins have
a tunica intima and a thin but continuous tunica media
what does the vena cava have a thick tunica adventitia which incorporates smooth muscle
why do veins contain the majority of blood in the body
Veins are flexible and can accommodate expansion,
what do Most small to medium sized veins have
valves that are inward extensions of the tunica intima.
