VASCULAR
SYSTEM
The cardiovascular system is concerned with the
transport of blood and lymph through the body. It may be divided into four
major components: the heart, the macrocirculation, the microcirculation
and the lymph vascular system.
Essentially, the macrocirculation comprises all
vessels, both arteries and veins, that would be visible to the eye. The vessels
of the macrocirculation supply and drain a network of fine vessels interposed
between them, the capillaries. This network is also called the capillary bed. Water and other components of the blood
plasma which exude from the blood vessels form the interstitial fluid, which is
returned to the circulation by the lymph vascular system.
General Structure of Blood Vessels
You have already seen blood vessels of various sizes
and types in preparations available in other lab sessions, and you should be
aware that the histological appearances of vessels of different sizes
(arterioles vs. arteries) and different types (arteries vs. veins) are
different from each other. These differences are the result of quantitative
variations of a common structural pattern that can be
seen in all blood vessels with the exception of capillaries, i.e. the division
of the walls of the blood vessels into three layers or tunics.
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The tunica intima
delimits the vessel wall towards the lumen of the
vessel and comprises its endothelial lining
(typically simple, squamous) and associated connective
tissue. Beneath the connective tissue, we find the internal elastic lamina, which delimits the tunica
intima from
the tunica media.
The tunica media is formed by a layer of circumferential smooth muscle and variable amounts of
connective tissue. A second layer of elastic
fibers, the external elastic lamina, is located
beneath the smooth muscle. It delimits the tunica media from
the tunica adventitia,
which consist mainly of connective
tissue fibres. The tunica adventitia blends with the connective tissue
surrounding the vessel. The definition of the outer limit of the tunica
adventitia is therefore somewhat arbitrary.
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![thumbnail]( "General Structure of Blood Vessels")
Title:
General Structure of Blood Vessels
by:
om
at
2013-02-15T03:13:00+07:00
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General Structure of Blood Vessels