Question

Which among the following is the hallmark of acute inflammation?

• A. Vasoconstriction
• B. Stasis
• C. Vasodilation and increase in permeability
• D. Leukocyte margination

Hint:

The defining vascular change brings more blood in and lets exudate leak out.

Answer 1

The Correct Option is C

Step 1: Acute inflammation has two central vascular components: alterations in vascular calibre that increase blood flow, and changes in the microvasculature that allow plasma proteins and leukocytes to leave the circulation.
Step 2: After a brief, transient vasoconstriction, arteriolar vasodilation occurs (mediated by histamine and nitric oxide), increasing blood flow and causing heat and redness.
Step 3: Increased vascular permeability follows, mainly through endothelial gap formation in venules, allowing protein-rich fluid (exudate) to escape into tissue, producing swelling.
Step 4: These two events, vasodilation and increased permeability, together constitute the defining vascular hallmark of acute inflammation. Stasis and leukocyte margination are downstream consequences, and vasoconstriction is only a fleeting initial event.
Conclusion: The hallmark is vasodilation with increased permeability, so the answer is option 3.