Blood clotting requires a complex series of chemical reactions and body signals.  This makes sense if you consider the problems that would occur if blood clots formed at the wrong times and the wrong places (for example: stroke, heart attack, pulmonary embolism).  The liver is the only organ that produces the majority of the "clotting factors" (blood clot proteins).  Only factor VIII (factor 8) is produced elsewhere, in the blood vessel walls.  The liver also produces many of the proteins that break up clots (fibrinolytics).  Platelets also play a key role in helping "gum up" the sites of blood vessel damage.  A constant balance between pro-clotting factors and anti-clotting factors are needed to prevent excess clotting in the event of injury to blood vessels.

Why is blood clotting so important?

Without the ability to plug holes in damaged blood vessels, a person could lose 100% of their blood from a small scratch.  Obviously, this would not be good.  Children with hemophilia lack a key protein that helps with blood clotting.  They can have large amounts of bleeding and bruising from mild injuries or even daily activities (for example, teeth brushing). 

Why are blood clot "breakers" necessary?

Blood clot "breakers" are known as fibrinolytics.  Fibrin is a stringy net that holds back red blood cells and helps platelets clump together.  "Lytic" means "break up into pieces."  Without fibrinolytics, all the blood in your body would become a giant mass of jelly-like clot after even a mild injury.  Fibrinolytics help limit clotting to the site of injury and also help break up blood clots when they are no longer needed.

What is the coagulation cascade?

Coagulation is a fancy term that means blood clotting.  The cascade is group of chemical reactions that when drawn on paper look like a waterfall or a line of dominos that fall one-by-one down a hill.  The purpose of the coagulation cascade is to provide several check points in the clotting process.  This keeps one simple chemical from controlling the entire process.

What are the two parts of the coagulation cascade?

The coagulation cascade is divided into two parts, the intrinsic pathway and the extrinsic pathway.

The intrinsic pathway is triggered when blood comes into contact with body tissues outside the blood vessels.

The extrinsic pathway is triggered by tissue factor, a protein released in response to tissue injury.

What are signs of a clotting or bleeding disorder?

Perhaps the most obvious way is to see how long it takes for an injury to stop bleeding.  Also, it is important to know if the child bleeds in unusual places (for example, blood in the stools or urine), at unusual times (with simple tooth brushing) or in unusual amounts (severe nose bleeds).  It is also important to know if the child bruises in unusual places (for example, on the back or belly) or if bruises are unusual large.  If clotting function is abnormal, small pin point bruises called petechiae can form in places where there is pressure on the skin (under a backpack strap) or can appear for no apparent reason.

Are there tests for clotting problems?

There are several blood tests available to screen for clotting disorders.  A "coagulation" panel includes the partial thromboplastin time (PTT) and prothrombin time (PT).  Also, an INR is a calculated measure that measures clotting.  A platelet count is used to determine if bleeding is related to a low number of platelets.  A red blood cell count can help determine how severe the blood loss has been.

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