Classification of Blood Vessels

Blood Vessels

These are hollow tubular vessels in which the blood flows.

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These are three types.

Arteries

• These are thick-walled and deeply located blood vessels, which always carry the blood away from the heart to various, body parts. these have narrow lumen but do not have valves. in them, the blood flows at high pressure and high speed. these generally carry oxygenated blood.

Veins

• These are thin-walled and superficially located blood vessels, which always carry the blood from various, body parts generally to the heart. these have wider lumen and valves in them to prevent backflow of blood. in them, blood flows at low pressure and low speed.

Capillaries

• These are thinnest blood vessels. and formed by division and redivision of arteriole inside the body organs. each is lined by a single layer of flat cells called the endothelium, which allows exchange off materials between blood and the body cells through tissue fluid.

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Structure of Blood Vessels

• A blood vessel ( artery or vein) is formed of three layers., these are tunica Interna tunica media and tunica external.
• Tunica Interna is the innermost layer and is formed of inner endothelium of flat cells and outer elastic membrane of yellow fibrous tissue.
• Tunica media is the middle layer and is formed of circular smooth muscles fibres and elastic yellow fibres.
• Tunica Externa is the outermost layer and is formed of collagen-rich areolar connective tissue.

Difference Between Artery and Vein

Artery	Vein
1) Endothelial cells of tunica interna are more flattened.	1) Endothelial cells of tunica interna are less flattened.
2) The elastic membrane of tunica interna is more developed so is more elastic.	2) The elastic membrane of tunica interna is less developed so is less elastic.
3) Tunica media is better developed so is more contractile.	3) Tunica media is less developed so is less contractile.
4) Tunica externa is less developed so is less strong.	4) Tunica externa is more developed so is more strong.
5) Lumen is small.	5) Lumen is large.