Blood Thinners: From Heparin to Plavix
Three types of blood cells exist in the human body: red blood cells, white blood cells, and platelets, in addition to plasma, which takes up 55 percent of the blood’s volume. Red blood cells take up approximately 45 percent of the blood’s volume. They transport oxygen from the lungs to other body parts. White cells defend us against bacterial and viral invasions. Platelets (less than 1 percent of the blood), the third type of blood cells, are sticky little cell fragments that are involved in helping the blood clot, a process known as coagulation. Without platelets (even though they constitute less than 1 percent of blood), our blood would not be able to clot, and we would have uncontrolled bleeding. However, formation of blood clots is a double-edged sword. Clots are beneficial because they heal cuts and wounds; blood clots in the bloodstream are harmful because they block coronary arteries, constrict vital oxygen supplies, and cause heart attacks and strokes, more and more frequent modern maladies as the baby boomers get older. Whenever the body is cut or injured and blood comes into contact with cells outside the bloodstream, a tissue factor on these cells encounters a particular protein within the blood, which triggers the clotting process. In the same vein, a series of other blood factors then come into action and amplify one another to quickly form a jelly-like blood clot. Blood clots form when an enzyme called thrombin marshals fibrin (a blood protein) and platelets (tiny cells that circulate in the blood) to coagulate at the site of an injury. Individuals with no ability to clot have a genetic condition called hemophilia; such people are also known as “bleeders.” Queen Victoria was hemophilic, and she passed on her genes to her many heirs who ruled Europe for over a century. This is why hemophilia is sometimes known as the royal disease. Symptoms of hemophilia manifest only in male offspring. People with hemophilia must periodically administer a clotting factor to their blood to prevent constant bleeding.