BLOOD

There are 5.5 liters of blood in the human body, and it accounts for about 8% of a body’s weight. 

Blood consists of 2 parts: liquid and solid.  The solid part is 2% white blood cells (WBC’s) and platelets, 43% red blood cells (RBC’s), and 55% plasma. 

Plasma consists of 92% water and 8% cellular waste, salt, and digested food.   

There are over 27 trillion RBC’s in the body. RBC’s are produced every second in the marrow of long bones.   

In a single drop of blood there are about 5 million RBC’s, so small that it would take 2,500 of them lined up in a row to stretch across the face of a dime. 

RBC'S

RBC’s  live 30-120 days.  After that time, they break apart and are removed by the spleen. An average person makes and loses about 8 million blood cells every second. 

It takes between 20 to 60 seconds for a RBC to travel around the body. In a  single day, a blood cell can travel 12,000 miles, which is 4 times across the US from coast to coast.   

WBC’s are much larger than RBC’s. WBC’s help defend against bacteria and infection. They go to damaged areas by following chemical signals given off by infected cells. 

WBC'S

Hemoglobin is a substance found in mature RBC’s. Oxygen attaches itself to hemoglobin to be carried to all the cells in the body.  It is hemoglobin which given RBC’s their red color. 

Platelets stick to each other and to edges of torn blood vessels. They release a sticky protein that forms a clot and allows healing. 

PLATELETS

Without platelets, a person could bleed to death from a small cut.  

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