ch. 20: the circulatory system blood vessels and circulation Flashcards
general anatomy of blood vessels
3 principal categories of blood vessels
- arteries
- veins
- capillaries
3 principal categories of blood vessels
arteries
carry blood away from heart
3 principal categories of blood vessels
veins
carry blood back to heart
3 principal categories of blood vessels
capillaries
connect smallest arteries to smallest veins to create a circuit
the vessel wall
walls of arteries and veins have 3 layers called
tunics
* tunica interna (tunica intima)
* tunica media
* tunica externa (tunica adventitia)
the vessel wall
tunica interna
(tunica intima)
lines the bood vessel and is exposed to blood
consists of the endothelium–simple squamous epithelium
- selectively permeable barrier
- secretes chemicals that stimulate dilation or constriction
- normally repels blood cells and platelets to prevent clotting
- when tissue around vessel is inflames, endothelial cells produce cell-adhesion molecules
- cell adhesion causes leukocytes to congregate in tissues where their defensive actions are needed
the vessel wall
tunica media
- middle layer
- consists of smooth muscle, collagen, elastic tissue
- strengthens vessels and prevents blood pressure from rupturing them
- contraction of muscle controls blood vessel diameter
the vessel wall
tunica externa
(tunica adventitia)
- outermost layer
- consists of loose connective tissue that often merges with that of neighboring blood vessels, nerves, or other organs
- anchors the vessel and provides passage for small nerves, lymphatic vessels
- vasa vasorum–small vessels that supply blood to outer half of wall in the larger vessels
arteries
arteries are divided into 3 classes
- conducting (elastic or large) arteries
- distributing (muscular or medium) arteries
- resistance (small) arteries
arteries
conducting (elastic or large) arteries
- biggest arteries
-
internal elastic lamina at the border between tunica interna and media
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