Contents
[hide]Blood vessels | |
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Simple diagram of the human circulatory system | |
Latin | vas sanguineum |
Anatomy
The arteries and veins have different structures, veins having two layers and arteries having three:- Tunica intima (the thinnest layer): a single layer of simple squamous endothelial cells glued by a polysaccharide intercellular matrix, surrounded by a thin layer of subendothelial connective tissue interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.
- Tunica media (the thickest layer): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel.
- Tunica adventitia: entirely made of connective tissue. It also contains nerves that supply the vessel
Capillaries consist of little more than a layer of endothelium and occasional connective tissue.
When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis (pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages.
Types
There are various kinds of blood vessels:
- Arteries
- Aorta (the largest artery, carries blood out of the heart)
- Branches of the aorta, such as the carotid artery, the subclavian artery, the celiac trunk, the mesenteric arteries, the renal artery and the iliac artery.
- Arterioles
- Capillaries (the smallest blood vessels)
- Venules
- Veins
- Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein.
- Venae cavae (the 2 largest veins, carry blood into the heart)
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