A 24-year-old healthy man sustains a superficial laceration to his left index finger while preparing food. Minor bleeding occurs but completely ceases within a few minutes. This normal physiological response involves a highly coordinated series of vascular, cellular, and protein-mediated events. Arrange the following steps of the normal hemostatic process in the correct chronological order, beginning immediately after the initial endothelial disruption.
- 1Reflex vasoconstriction mediated by local neural reflexes and endothelin release
- 2Binding of platelet glycoprotein Ib (GpIb) to exposed subendothelial von Willebrand factor (vWF)
- 3Release of adenosine diphosphate (ADP) and thromboxane A2 from platelet granules
- 4Platelet aggregation through glycoprotein IIb/IIIa cross-linking with fibrinogen
- 5Thrombin-mediated cleavage of fibrinogen into insoluble fibrin strands
Answer
The correct chronological sequence of hemostasis begins with reflex vasoconstriction, followed by platelet adhesion via GpIb, platelet degranulation, platelet aggregation via GpIIb/IIIa, and finally fibrin mesh formation via thrombin.
The biological process of hemostasis strictly follows a timeline designed to rapidly stop bleeding while building a durable seal. It starts with transient vasoconstriction. Next, primary hemostasis occurs: platelets adhere to vWF via GpIb, become activated and release granules (ADP, TXA2), and then aggregate using GpIIb/IIIa and fibrinogen. Finally, secondary hemostasis solidifies this temporary plug when thrombin converts fibrinogen into a cross-linked fibrin mesh.
Step-by-Step Solution
Key Concept
The physiologic phases of hemostasis occur sequentially: vascular spasm, primary hemostasis (platelet adhesion, activation, and aggregation), and secondary hemostasis (coagulation cascade leading to fibrin deposition).