00:00 / 00:00
James West is a 14-year-old male client with a history of hemophilia type A. He was brought to the emergency department, or ED, by his grandmother, Mrs. West, after falling off his skateboard.
James states that he was wearing a helmet and protective pads over his elbows and knees but that he fell onto his buttocks while learning a new skateboarding trick.
He says that it hurts to sit down or bend his left leg at the hip. Hemophilia is a group of genetic bleeding disorders caused by deficiencies in various coagulation factors.
Normally, after a tissue injury, there’s an immediate constriction of the blood vessel to limit the amount of blood flow and loss.
After that, platelets start adhering to the injured vessel wall to form a plug, and the coagulation cascade is activated.
First off in the blood there’s a set of clotting factors, most of which are proteins synthesized by the liver, and usually these are inactive and just floating around the blood.
The coagulation cascade starts when one of these proteins gets activated. This active protein then activates the next clotting factor, and so on.
Now, the coagulation cascade can get started in two ways. The first way is called the extrinsic pathway, and it starts when tissue factor gets exposed by the injury of the endothelium.
The tissue factor turns inactive factor VII into activated factor VIIa. Together, the tissue factor and the newly formed factor VIIa form a complex that turns factor X into active factor Xa.
Factor Xa, with factor Va as a cofactor, turns factor II, also called prothrombin, into factor IIa, also called thrombin.
Thrombin then turns factor I or fibrinogen, into factor Ia or fibrin, which precipitates out of the blood at the site of injury.
On the other hand, the intrinsic pathway starts when platelets near the blood vessel injury activate factor XII into factor XIIa.
Next, factor XIIa activates factor XI to factor XIa, which further activates factor IX to factor IXa.
Finally, factor IXa and factor VIIIa work together to activate factor X to factor Xa, and from that point, both the extrinsic and intrinsic pathways basically converge on a single final path called the common pathway.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.