24 Amazing facts about arteries and capillaries

Heart rate is universally related to body size: the bigger the animal, the slower its heart beats. Tweet This

Blood is up to 79% water. Tweet This

Before World War I, almost no medical doctors were heart specialists. Tweet This

Electrocardiograph (ECG) was invented in 1902 by Dutch physiologist Willem Einthoven. It is still used to observe heart’s rate and rhythm. Tweet This

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In 1929, German physician Werner Forssmann invented the procedure Cardiac catheterization. He first performed it on himself. Tweet This

On Earth, blood tends to pool in the legs because of gravity. In space, it stays in the chest and head. That’s why astronauts have puffy faces. Tweet This

Skin gets 13% of all blood supply. Tweet This

Microscopic veins are called venules. Tweet This

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

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

Heart actually can keep beating after being removed from the body provided that it continues to receive oxygen. Tweet This

Unlike most other cells, red blood cells have no nuclei and thus are able to carry more oxygen. However, they cannot divide. Tweet This

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All blood vessels’ combined length is close to 100,000 km (60,000 miles). Capillaries alone contribute for 85% of this length. Tweet This

Veins, arteries and capillaries are the three types of blood vessels in the circulatory system. They transport blood containing oxygen, antibodies, nutrients, electrolytes and hormones. Tweet This

Blood vessels also transfer heat from blood to body organs. Tweet This

There are three main types of arteries: elastic (large), muscular (medium) and arterioles (small). Tweet This

Arterioles are less than half millimetre in diameter, barely visible to human eye. Tweet This

Blood vessels’ diameter is ranging from 25 mm (one inch) in aorta to only 6 μm in capillaries. Tweet This

Thickness of blood vessel walls is only one single cell in capillaries. Tweet This

Most veins and arteries can dilate or constrict in response to nervous and chemical stimuli. Tweet This

Adrenaline redirects blood to muscles and prepares the body for “fight or flight” response.  Tweet This

Large arteries’ pale yellow colour is due to the elastic fibres, making up to 50% of arteries’ walls. Tweet This

Small arteries and arterioles determine blood pressure. Tweet This

Blood pressure is measured in arteries. First (higher) number is the systole phase, when your heart beats. Second is the diastole, when your heart is relaxed between beats. Tweet This