Vein Anatomy

- Veins are blood vessels that carry blood back to the heart. Veins are unlike arteries in that they are:

• Superficial: they lie close to the skin surface and can be seen as dark red lines
• Non-pulsatile: they do not have a rhythmic contraction that can be felt
• Valved: they have one-way valves that prevent backflow of blood

- Veins have three layers of tissue:

• Tunica adventitia: the outermost layer that provides support and protection
• Tunica media: the middle layer that contains smooth muscle and elastic fibers
• Tunica intima: the innermost layer that lines the lumen (space) of the vein and prevents clotting