Today is Blood Appreciation Day (not really)—and we’re about to give this vital bodily fluid some love.
Most people’s understanding of blood is that they have it, they know they need it to live, and it sometimes comes out when you hurt yourself or you donate it. But blood is so much more than just that red stuff inside of you.
Here are 10 incredible facts about this specialized, life-giving bodily fluid:
1. Blood is a unique and vital substance that cannot be artificially made.
There is no substitute for blood, and it cannot be made or manufactured. That’s why donating blood is so important: It’s the only way to give blood to patients who need it.
2. The blood in your veins is a mixture of about 55 percent plasma and 45 percent blood cells.
Plasma is a yellowish liquid made up of water, sugar, fat, protein, and salts. Its main job is to transport blood cells throughout the body, along with nutrients, waste, antibodies, hormones, and proteins that help maintain the body's fluid balance.
The other half of your blood consists of blood cells: red blood cells, white blood cells, and platelets.
3. Blood cells fight infection, carry oxygen, and help control bleeding.
Blood cells have many important jobs:
Red blood cells disperse oxygen and nutrients to your lungs and tissues. According to the American Society of Hematology, red blood cells are the most abundant cell in the blood, accounting for about 40 to 45 percent of its volume.
White blood cells carry cells and antibodies throughout the body to fight infection. There are much fewer white blood cells than red blood cells—they only account for 1 percent of blood volume.
Platelets aren’t technically cells; they’re small fragments of cells. Platelets help the blood clot when you’re injured by gathering at the site and sticking to the lining of an injured blood vessel. This process covers the wound and prevents blood from leaking out.
4. Blood cells die constantly, and your body makes new ones in your bone marrow.
Red blood cells, white blood cells, and platelets are produced in the marrow of your bones, specifically in the vertebrae, ribs, hips, skull, and sternum.
Your body makes about 2 million new red cells every second. For white blood cells in platelets, it often takes a few days.
5. Blood cells have vastly different lifespans.
Red blood cells live the longest, about 120 days, and platelets live for about 6 days. Some white blood cells live less than a day, but others live longer.
6. A protein in red blood cells is what gives blood its red hue.
Ever wonder why blood is red? You can thank hemoglobin for that. Hemoglobin helps transport oxygen from the lungs to the rest of the body, and then returns it as carbon dioxide so it can be exhaled.
Even though blood is red, it does change its shade as it travels throughout the body—sometimes it’s bright red, sometimes it’s dark red. The brightness of the red is determined by how much oxygen is in the blood. Blood coming directly from the heart is oxygen-rich and bright red, and as the blood circulates and oxygen is removed by tissue, the blood becomes darker.
7. Once blood is pumped out of the heart, it takes 20-30 seconds to circulate throughout the body and back to the heart.
That means in a single day, your blood circulates throughout your entire body about 2,880 times.
8. About 7 percent of your body weight is blood.
That’s almost four times as much as your brain.
9. An average-sized man has about 12 pints of blood in his body, and a woman has about 9 pints.
During a blood donation, the average person gives about 1 pint of blood, which is roughly 10 percent of your total blood.
10. Every 2 seconds someone in the U.S. needs blood—and just 1 pint of donated blood can save 3 lives.
About 5 million patients receive blood transfusions each year, according to the Centers for Disease Control and Prevention. That’s one person every two seconds. If you are able, consider donating your blood—no matter what your blood type. Learn more about preparing to donate blood safely here.