Question

How far can veins stretch?

Answer 1

Three types of blood vessels makeup human circulatory system: veins, arteries and capillaries. All the three vessels transport oxygen, blood, nutrients, and hormones to cells and organs. While the arteries carry the oxygenated blood from the heart, veins carry the oxygen depleted blood from the tissues back to heart.

Complete answer:
Veins carry oxygen depleted blood back to heart. They’re similar to arteries but not as thick or strong as the arteries. Unlike the arteries, veins contain valves that make sure blood flows only in one direction. As the pressure from the heart is strong, arteries do not require valves, hence blood is only able to flow in one direction. Valves also help blood travel back to heart against the force of gravity. Veins hold about 65 percent of our body's blood.
If we lay out all of the arteries, veins and capillaries in one adult, end-to-end, they would stretch around 60,000 miles (100,000 kilometers). The capillaries, which are the smallest of the three blood vessels, would make up around 80 percent of this length. The circumference of our Earth is about 25,000 miles (40,000 km). Which means that a person's blood vessels could wrap around our planet approximately 2.5 times.

Note: There are four types of veins: Deep veins, superficial vein, systemic veins and Pulmonary veins. Deep veins are located within the muscle tissue. Superficial veins are closer to the skin's surface. Pulmonary veins transport blood that has been filled with oxygen by lungs to the heart. Systemic veins are located throughout our body from the legs up to the neck, including the trunks and arms.