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Humans can't live without blood. Without blood, the body's organs couldn't get the oxygen and nutrients they need to survive, we couldn't keep warm or cool off, fight infections, or get rid of our own waste products. Without enough blood, we'd weaken and die.

Here are the basics about the life-sustaining fluid called blood.

What Is Blood and What Does It Do?

Blood brings oxygen and nutrients to all the parts of the body so they can keep working. Blood carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body. Blood also fights infections, and carries hormones around the body.

Blood is made up of blood cells and plasma. Plasma (PLAZ-muh) is a yellowish fluid that has nutrients, proteins, hormones, and waste products. The different types of blood cells have different jobs.