Arrange the following steps in order of the events occurring first to lastA. MarginationB. Rolling C. StasisD. Pavementing
**Core Concept**
The process described is the sequence of events in the pathogenesis of inflammation, specifically the steps involved in the extravasation of leukocytes from the bloodstream into the tissue space.
**Why the Correct Answer is Right**
The correct sequence of events is crucial for understanding the inflammatory response. It begins with stasis (A), where the leukocytes slow down in the blood vessels due to an increase in the permeability of the endothelial layer. This is followed by margination (B), where the leukocytes adhere to the endothelial wall, preparing to migrate through the vessel wall. Rolling (C) occurs next, where the leukocytes weakly adhere to the selectin molecules on the endothelial surface, allowing them to move along the vessel wall. Finally, emigration or diapedesis (pavementing) occurs last (D), where the leukocytes migrate through the endothelial layer and into the tissue space, where they can perform their immune function.
**Why Each Wrong Option is Incorrect**
**Option A:** Stasis occurs first in the sequence, not last. It is the initial step where leukocytes slow down in the blood vessels.
**Option B:** Margination occurs after stasis, not before. It is the step where leukocytes adhere to the endothelial wall.
**Option C:** Rolling occurs after margination, not before. It is the step where leukocytes weakly adhere to the selectin molecules on the endothelial surface.
**Clinical Pearl / High-Yield Fact**
Remember the sequence of events in inflammation as "STAMP" - Stasis, Transmigration (margination), Adhesion (rolling), Migration (pavementing, emigration). This mnemonic will help you recall the correct sequence of events in the inflammatory response.
**Correct Answer:** D. Pavementing