In the coagulation cascade the clot is initiated by negatively charged paicles on the glass bead. It is in-vivo initiated by:
**Core Concept**
The coagulation cascade is a complex process involving multiple factors and pathways that lead to the formation of a blood clot. It can be initiated through two main pathways: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway is activated by negatively charged surfaces.
**Why the Correct Answer is Right**
The correct answer is related to the intrinsic pathway of coagulation, which is initiated in vivo by negatively charged particles or surfaces, such as those found on damaged endothelial cells or platelets. This pathway involves factors such as factor XII (Hageman factor), factor XI, and factor IX, which are activated in a sequential manner.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not accurately describe the initiator of the intrinsic coagulation pathway.
**Option B:** This choice is incorrect because it is not directly related to the initiation of coagulation.
**Option C:** This choice is incorrect because it is related to a different aspect of coagulation.
**Clinical Pearl / High-Yield Fact**
The intrinsic pathway of coagulation is crucial for understanding bleeding disorders and coagulopathies. Remember that the intrinsic pathway is activated by internal factors within the blood itself, such as damaged endothelial cells.
**Correct Answer:** D. Negatively charged particles on damaged endothelial cells.