Don't have a nucleus, which means more space for hemoglobin and oxygen
Shaped like a biconcave disc, which gives them a large surface area for absorbing oxygen
White blood cells

Essential part of the immune system, defend against infection
How white blood cells defend against pathogens
Phagocytosis (engulf/consume microorganisms)
Produce antibodies that bind to and help destroy pathogens
Produce antitoxins that neutralize toxins produced by pathogens
White blood cells

Have a nucleus, unlike red blood cells
Platelets

Small fragments of cells that float in the blood and help stop bleeding by clotting
Plasma

Pale straw-colored liquid that makes up over half the blood's volume, carries nutrients, waste, hormones, antibodies, and other substances
Most adults have about 5 liters of blood flowing through their circulatory system at any one time
Artificial blood

Blood substitute consisting of salt water, adds volume to the circulatory system but doesn't contain red blood cells so can only replace about 1/3 of the blood
Blood transfusion

Giving a person real blood that has been donated, provides red blood cells to survive blood loss
