Histology Flashcards
what are the three basic layers of blood vessels?
Inner layer - tunica intima
middle layer - tunica media
outer layer - tunica adventitia
what is the inner layer of blood vessels made of?
a single layer of squamous epithelial cells supported by .a basal lamina and a thin layer of connective tissue.
what is the middle layer of blood vessels made of?
smooth muscle. thickness varies.
what is the outer layer of blood vessels made of?
made up of supporting connective tissue.
what is the tunica intima and tunica media separated by?
a layer of elastic tissue called the internal elastic membrane.
what is the tunica media and tunica adventitia separated by?
a layer of elastic tissue called the external elastic membrane.
what are the largest arteries (e.g. aorta) termed? and why?
elastic arteries, because they have many sheets of elastic fibres in their tunica media to provide elastic recoil.
In large vessels, only the inner part of the wall can obtain nutrients from the lumen, therefore some those vessels will have to have their own supply, what is it called?
vasa vasorum
how many layers of smooth muscle do arterioles have in their tunica media?
one or two.
what are capillaries composed of?
endothelial cells and a basal lamina
what do capillaries often have at intervals just outside the basal lamina? what are they?
pericytes - connective tissue cells that have contractile properties.
what are the three different types of capillaries?
continuous capillaries
fenestrated capillaries
sinusoidal or discontinuous capillaries
what are the properties of the three types of capillaries?
- continuous capillaries are more common
- fenestrated capillaries have approx 50nm pore in walls
- sinusoidal capillaries lack a basal lamina and have large gaps through which macromolecules and in some cases even cells, can pass.
where can the three types of capillaries be found?
- continuous capillaries - muscle, connective tissue, lung, skin, nerve
- fenestrated capillaries - mucosa of the gut, endocrine glands, glomeruli of the kidney.
- sinusoidal capillaries - liver, spleen and bone marrow.
what are post-capillary venules?
capillary networks drain into them. they are endothelial cell-lined and contain a thin layer of connective tissue and occasional pericytes. these are important sites for exchange e.g. cells moving into the tissue in inflammation.
when are vessels referred to as venules?
once they begin to acquire intermittent smooth muscle cells in their tunica media layer.
what are the properties of veins?
have a tunica intima, a relatively thin but continous tunica media typically consisting of a few layers of smooth muscle. the tunica media is markedly thinner than would be found in a muscular artery.
what type of vessel contains most of the blood in the body?
vein
what are the three layers of the heart?
endocardium - inner layer
myocardium - middle layer
epicardium - outer layer
what is the structure of the endocardium?
endothelium
basal lamina
thin layer of collagen fibres
layer of denser connective tissue.
what is a subendocardium?
loose connective tissue containing small blood vessels and nerves and the branches of the impulse conducting system.
what is the structure of the myocardium?
bundles and layers of contractile cardiac muscle fibres.
individual muscle fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries.
what do intercalated discs passing across the fibres in the myocardium do?
acts to attach cells but also allows spread of electrical activity.
what is the epicardium?
a single layer of flattened epithelium called mesothelium.
