Interesting Facts About Blood Vessels: Veins Are Not Blue!

When people think of the body’s circulatory system, the first thing that usually comes to mind is the heart. But the heart couldn’t do its job without blood vessels: a vast system of elastic tubes made of muscle.

This network of vessels carries blood to every part of your body, ensuring that your heart, lungs, and all vital organs get the oxygen and nutrients they need, the National Heart, Lung, and Blood Institute (NHLBI) explains.

A blood vessel is a tube that carries blood. Blood vessels that take blood away from the heart are arteries. Blood vessels that take blood back to the heart are veins. Capillaries are between veins and arteries and they supply tissue with blood. There are 100,000 miles of blood vessels in an adult human body.

The heart plus all of the blood vessels in the body together are called the circulatory system. Blood is moved by the pumping of the heart and carries oxygen to the tissues. The expansion of blood vessels is called vasodilation, it helps the body to get rid of heat energy. The constriction of blood vessels is called vasoconstriction, it prevents the body from losing warmth, thus keeping us nice and warm.

Here are some interesting things you may not know about the vast network that carries blood throughout the body.



1. Capillaries spit out blockages in blood. Capillaries in the brain can expel obstructive debris. This debris may consist of cholesterol, calcium plaque, or clots in the blood. Cells within the capillary grow around and enclose the debris.

The capillary wall then opens up and the obstruction is forced out of the blood vessel into the surrounding tissue. This process slows down with age and is thought to be a factor in cognitive decline that occurs as we age. If the obstruction is not completely removed from the blood vessel, it can cause oxygen deprivation and nerve damage.

2. Veins are not blue. They appear that way as only blue light could penetrate the skin and reflect back to your eyes without being absorbed by the skin.

3. Blood in veins is dark red because it holds very little oxygen.

4. The smallest blood vessels measure only five micrometers. To give you some perspective, a strand of human hair measures about 17 micrometers.

5. There are lots of blood vessels attached to your heart. Blood vessels that carry blood to your heart are called veins; vessels that carry blood away from your heart are called arteries. There are a couple of really big veins and arteries in your body – the vena cava (superior and inferior, or above and below) is the vein that collects blood from all other veins and brings it to the heart; the aorta is the big artery that carries the blood from your heart to all the other arteries in your body.

6. There is only one vein in the entire body that carries oxygen-rich blood; it is called the pulmonary vein, and it brings blood from the lungs to the left side of your heart. Also, there is only one artery in your body that carries oxygen-poor blood; it is called the pulmonary artery, and it carries blood from the right side of your heart to your lungs.

7. They carry a million barrels of blood in a lifetime. The blood in your body is continuously flowing. Every day, your heart pumps about 1,800 gallons of blood through your blood vessels, the NIA states. Over the course of a lifetime, this vast system carries about a million barrels of blood throughout the body.

8. Blood vessels are affected by the weather. The circulatory system helps maintain body temperature. Blood vessels expand to release heat, allowing you to cool down, and narrow or constrict to conserve heat, according to the National Library of Medicine.

In extreme cases, such as when your feet are exposed to very cold or wet conditions for prolonged periods of time — a condition called trench foot — the constriction of blood vessels can shut down circulation, causing skin tissue to die, according to the U.S. Centers for Disease Control and Prevention. Another consequence of extreme exposure is frostbite, which can happen after just a few minutes in freezing conditions.

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