vEINS

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Veins

Veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart.

Veins are less muscular than arteries and are often closer to the skin. There are valves in most veins to prevent backflow.

Veins are present throughout the body as tubes that carry blood back to the heart. Veins are classified in a number of ways, including superficial vs. deep, pulmonary vs. systemic, and large vs. small.

Superficial veins are those closer to the surface of the body, and have no corresponding arteries.

Deep veins are deeper in the body and have corresponding arteries.

Perforator veins drain from the superficial to the deep veins. These are usually referred to in the lower limbs and feet.

Communicating veins are veins that directly connect superficial veins to deep veins.

Pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the heart.

Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

Most veins are equipped with one-way valves, similar to a Duckbill valve, to prevent blood flowing in the reverse direction.

Veins are translucent, so the color a vein appears from an organism's exterior is determined in large part by the color of venous blood, which is usually dark red as a result of its low oxygen content. Veins appear blue because the subcutaneous fat absorbs low-frequency light, permitting only the highly energetic blue wavelengths to penetrate through to the dark vein and reflect back to the viewer. The colour of a vein can be affected by the characteristics of a person's skin, how much oxygen is being carried in the blood, and how big and deep the vessels are.[2] When a vein is drained of blood and removed from an organism, it appears grey-white

 

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