Blood Vessels

Q:  What are the differences between veins, arteries, and capillaries?  What are varicose veins and what are the causes?

A:  The cardiovascular system consists of the heart, blood vessels, and blood.  The blood vessels transport oxygen, nutrients, hormones, and cellular waste products throughout the body.  The three main blood vessels are arteries, veins, and capillaries.  The chart below details the primary differences between these vessels.

Arteries

-Carries oxygenated blood 

away from the heart

-No valves

-High pressure

-Thick walls and muscle fiber

to withstand pressure

Veins

-Carries de-oxygenated blood

to the heart

-Valves

-Low pressure

-Thin walls and muscle fiber

due to low pressure

Capillaries

-Fed from arteries

-Smallest and thinnest vessel

-Most common vessel

-Supplies oxygenated blood to tissues 

of the body

Varicose veins are twisted, enlarged veins that form near the surface of the skin and are most common in the lower extremities.  As noted above, veins have valves to ensure de-oxygenated blood flows away from the tissue and back to the heart.

Varicose veins form for various reasons but the most common causes are due to vein valve deterioration, vein muscle weakening due to age, and pregnancy.  Instead of flowing back to your heart, the blood starts to pool in your veins which causes them to become enlarged. The veins appear blue because of the de-oxygenated blood.

The following websites were used as references in answering the question:

http://thecardiovascularsystem.wikispaces.com/Differences+between+Arteries,+Capillaries+and+Veins

http://www.innerbody.com/image/cardov.html

http://www.mayoclinic.org/diseases-conditions/varicose-veins/basics/causes/con-20043474