What blood is—and why it matters

Blood components

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• Platelets

  Platelets constitute a small percentage of total blood volume.

  What do they do?	Control bleeding and promote clotting by forming clusters to plug small holes in blood vessels.
  Whose lives are saved?	Patients with leukemia or those undergoing major surgery, and liver and bone marrow transplant recipients.

• Red blood cells

  Red blood cells make up approximately 45% of blood volume. A few drops of whole blood contain about one billion red blood cells.

  What do they do?	Carry oxygen throughout the body.
  Whose lives are saved?	Accident victims, organ and bone marrow transplant recipients, premature infants, people battling sickle cell disease, cancer patients, and adults undergoing open heart surgery.

• Plasma

  Plasma is a pale yellow mixture of water, proteins, and salts that constitutes 55% of blood volume.

  What does it do?	Acts as a carrier for blood cells, nutrients, enzymes, and hormones; adds to the total volume of blood and replaces fluids.
  Whose lives are saved?	Severe burn victims, cardiac surgery patients, liver transplant recipients, and patients suffering from shock or with blood clotting problems.