consist of three layers of different types of cells:
1. the innermost, intima,
2. the media,
3. the outermost, adventitia.
A. The intima is comprised of a single layer of endothelial cells
embedded in an extracellular matrix.
media is separated from the intima by the internal elastic lamina,and
consists of smooth muscle cells,elastic laminae,bundles of collagen
fibers and elastic fibrils,all embedded in an extracellular
adventitia is the most variable layer, containing dense fibroelastic
tissue, nutrient vessels, and nerves.
actual composition of each of these layers varies with the type
of blood vessel.
conduit arteries are referred to as elastic ones,because of
their high ratio of elastic laminae to smooth muscle cells.
Muscular arteries are smaller and have a prevalence of smooth
Arterioles consist of only one or two layers of smooth muscle
smallest vessels are the capillaries,made up of a single layer
of endothelial cells, that are occasionally apposed to pericytes-smooth
muscle-cells that serve a contractile function.
venous system has a similar architecture to that of the arterial
system above,the main difference being the orientation of the
smooth muscle cells within the wall.
The two most important cell types in the vascular system are
the endothelial cell and the vascular smooth muscle cell.
endothelial cell is generally oriented with the direction of
blood flow parallel to the main axis of the vessel. Endothelial
cells are held together by junctional complexes that regulate
permeability and control cell-to-cell communication.
smooth cell is a spindle-shaped cell, whose orientation varies
with the artery,but is generally helical in large, elastic arteries
and concentric in muscular arteries.