Arrange vascular events in acute inflammation: A. Increased blood viscosity B. Vasodilatation C. Stasis D. Vasoconstriction E. Increased vascular permeability
**Core Concept**
In acute inflammation, a complex cascade of vascular events occurs, leading to increased blood flow and permeability to immune cells and mediators. This sequence is crucial for the initiation and progression of the inflammatory response.
**Why the Correct Answer is Right**
The correct sequence of vascular events in acute inflammation begins with **vasodilatation** (B). This is due to the release of vasodilatory mediators such as bradykinin, histamine, and prostaglandins, which cause the smooth muscle of blood vessels to relax, leading to increased blood flow to the affected area. Following vasodilatation, **increased vascular permeability** (E) occurs due to the action of various mediators, including histamine, bradykinin, and leukotrienes, which cause the gaps between endothelial cells to open, allowing fluid and immune cells to leak into the tissue. Stasis (C) is a consequence of vasodilatation and increased vascular permeability, as the increased fluid and cellular content in the tissue can impede blood flow. Finally, **increased blood viscosity** (A) and **vasoconstriction** (D) are not characteristic of the initial vascular events in acute inflammation.
**Why Each Wrong Option is Incorrect**
**Option A:** Increased blood viscosity is not a primary event in acute inflammation, as the inflammatory response is characterized by increased blood flow, not decreased viscosity.
**Option D:** Vasoconstriction is a response to injury, but it is not the initial vascular event in acute inflammation. In fact, vasoconstriction is often followed by vasodilatation in the inflammatory response.
**Clinical Pearl / High-Yield Fact**
In the context of acute inflammation, the sequence of vascular events can be remembered using the acronym "VIPS": Vasodilatation, Increased Vascular Permeability, Stasis, and finally, the consequences of increased fluid and cellular content in the tissue.
**Correct Answer:** B. Vasodilatation