*Arteries
*Veins
*Capillaries
Veins are a type of elastic blood vessel that return deoxygenated blood from body organs back to the heart. Arteries transport blood away from the heart while veins move blood back to the heart.
Deoxygenated blood that flows into the veins is collected within tiny blood vessels called capillaries. Capillaries are the smallest blood vessels in the body. These tiny blood vessels have thin walls. Capillaries are where oxygen and nutrients are exchanged for carbon dioxide and waste.
Veins can be categorized into four main types: pulmonary, systemic, superficial, and deep veins.
*Pulmonary veins carry oxygenated blood from the lungs to the heart
*Systemic veins return deoxygenated blood from the rest of the body to the heart.
*Superficial Veins: these veins work in unison to collect blood from skin and surrounding superficial tissues
*Deep Veins: Once blood enters these deep veins, blood is pumped to the heart as these large muscles contract, moving blood along the circulatory system
The main vein in your body is the vena cava. The superior vena cava is in the upper right part of human chest. It carries blood from head, neck, arms and chest back to the heart.
The walls of veins are made up of three different layers:
Tunica externa
Tunica media
Tunica intima
Functions of veins
