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.
apart from mesothelium what else does the epicardium contain?
basal lamina
fibroelastic connective tissue and in some places adipose tissue.
what are the two parts of the pericardium?
fibrous and serous pericardium
what is the fibrous pericardium?
a sac of tough fibrocollagenous connective tissue
what is the serous pericardium?
made up of a layer of simple squamous epithelium (termed mesothelium) backed by a basal lamina and connective tissue,
what is the serous pericardium which lines the inner surface of the fibrous pericardium called?
parietal serous pericardium
what is the serous pericardium which lines the heart called?
visceral serous pericardium
what is the parietal and visceral serous pericardium separated by?
pericardial cavity - which contains a small amount of pericardial fluid that provides lubrication for the heart movement.
what is the heart fibrous ‘skeleton’ formed from?
thick bands of fibrous connective tissue around the heart valves, between the atria and between the ventricles.
what does the heart fibrous ‘skeleton’ provide?
supports the valves and provides attachment for the cardiac muscle fibres.
what is the structure of heart valves?
- have an outer endothelial layer with basal lamina.
- layer of collagen and elastic fibres.
- a core of dense connective tissue called the lamina fibrosa, that is in continuity with the fibrous skeleton.
what are the leaflets of valves separating the atria and ventricles anchored by?
papillary muscles in the wall of the ventricle by collagenous strands called the chordae tendinaea, which merge with the lamina fibrosa.
what do heart valves not have?
blood vessels
what are the three types of cardiac muscle cells?
contractile cells
pacemaker cells
conducting cells
