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
An essential part of the immune system, which defends against infection
Functions of white blood cells
Phagocytosis (engulfing and consuming microorganisms)
Producing antibodies that bind to and help destroy pathogens
Producing antitoxins that neutralize toxins produced by pathogens
Platelets
Small fragments of cells that rush to wounds and act like a glue to patch up holes and stop blood from pouring out
Plasma
Pale straw-colored liquid that makes the blood watery so it can flow, and carries nutrients, waste products, hormones, proteins, and antibodies
Most adults have about 5 liters of blood flowing through their circulatory system at any one time
Artificial blood
A blood substitute that consists of salt water, which 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, which contains red blood cells to survive blood loss
