1.  Human blood is made up of four basic components: red blood cells, white blood cells, platelets and plasma.  (That makes one little drop seem pretty crowded.)

2.  Plasma, the fluid part of blood, takes up the most “space,” making up about 55% of the blood; most of plasma (92% is water), with the other 8% mostly various proteins.

3.  Red blood cells carry oxygen around the body, while white blood cells help to fight infection.  Platelets are important in clotting and stopping bleeding.  (Gee, even my blood makes me feel like I’m not doing anything important with my life!)

4.  Typically, blood is classified into 4 groups or “types” – A, B, AB and O.  (This grouping is called the ABO system.)  Each type can also be either negative or positive.  (And no, having negative blood does not make you think negative thoughts, an excuse my mother used to make about why I’m so crabby.)

5.  However, there are other ways of grouping blood which can offer more specific information about the antigens that can be found in the red blood cells of each type.

6.  In the United States, 40,000 pints of blood are transfused every day.

7.  The average person has between 8 and 12 pints of blood in his/her body.  (Judging by what my scales told me this morning, I must be a 12-pinter.)

8.  After a person makes a blood donation, the volume of the blood is replaced in 24 hours; red blood cells will be regenerated over a 4-8 week period.

9.  A person undergoing a bone marrow transplant may require platelets from over 100 donors and red blood cells from over 20 donors.  (And no, they’re not being greedy!)

10.  The first confirmed and documented example of a successful blood transfusion on a human occurred on June 15, 1667, when Jean-Baptiste Denys transfused the blood of a sheep into a 15-year-old boy; the first successful transfusion involving human blood was in 1818, performed by Dr. James Blundell.  (Sheep blood.  We’ve come a long way, baby!)