The human vascular system, is composed of the heart, blood, and blood vessels. The heart pumps blood through the blood vessels, delivering oxygen, nutrients, hormones, and removing cellular waste from all parts of the body. There are three different kinds of blood vessels: arteries, capillaries, and veins. Arteries branch off to form the tiny capillaries, which in turn link back up to form veins. Here are five fascinating facts about the human vascular system.
1. The heart is the body’s hardest working organ
The average heart is only about the size of a closed fist, but it pumps 4,000 gallons of blood through the body every day. The average heart beats at a rate of 70 times per minute at rest. It beats 30 million times a year; thats 2.5 billion beats throughout an average person’s life span. The heart is such a strong muscle that it only takes about 20 seconds for blood to circulate the entire body.
2. Blood has four components
The average person has 4-5 liters of blood; plasma makes up almost 55%. Plasma is the non-cellular, liquid blood component, made of 90% water. The other 10% are proteins and dissolved substances such as glucose, nutrients, electrolytes, and cellular waste products. Red blood cells make up nearly 45% of blood and are the most common type of blood cell. They are produced in the bone marrow and carry oxygen throughout the body. Platelets and white blood cells make up a much smaller percentage of blood volume but still play important roles. Platelets clot blood and form scabs, while white blood cells play an essential role in immune system function.
3. Your blood vessels could wrap around the planet
If the blood vessels in an adult human were stretched out end to end, they would be 100,000 miles long. By contrast the earth is just under 25,000 miles long. Therefore, the average person’s blood vessels could encircle earth up to four times!
4.Individual capillaries are thinner than hairs
The tiniest of capillaries measure only about 5 micrometers wide, a human hair is on average 17 micrometers. Some of these passageways are so minuscule that individual red blood cells have to distort themselves just to pass through.
5.Veins contain almost 70% of blood in the body
Veins can hold so much of the body’s blood at any given time because the are less rigid and thinner than those of arteries. This is because veins are carrying blood back to the heart, so the blood is being pushed along by much less pressure than it is in the arteries and capillaries.