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Vascular Development - Anatomy & Physiology (view source)
Revision as of 16:05, 10 July 2008
, 16:05, 10 July 2008no edit summary
The volume and pressure of blood flowing in the network dictates the degree of development of individual vessels. The channels which carry blood at high pressure develop additional tissue layers from the surrounding mesoderm thereby becoming thick-walled. The diameter of these vessels also increases and they become known as arteries. Differentiation of mesenchymal cells to smooth muscle is driven by growth factors released from endothelial cells.
The volume and pressure of blood flowing in the network dictates the degree of development of individual vessels. The channels which carry blood at high pressure develop additional tissue layers from the surrounding mesoderm thereby becoming thick-walled. The diameter of these vessels also increases and they become known as arteries. Differentiation of mesenchymal cells to smooth muscle is driven by growth factors released from endothelial cells.
===Development of the Arterial System===
The primitive heart is a simple tube with one inlet and one outlet and empties into embryonic structures called aortic arches. These are organised along the same lines as the blood vessels supplying the gills of fish. Most vertebrate embryos have six aortic arches but in the majority of mammals the fifth arch does not develop. Ultimately, some of the arches are remodelled whereas others atrophy. Not all of the arches are present simultaneously; the first and second develop before the fourth and sixth and by the time the sixth pair of arteries have formed, very little of the first two pairs remains. Major changes to the aortic arches occur between the third and fourth week of gestation in dogs and between the third and seventh week in horses.