Increased permeability of the vessel walls in an inflammation causes which signs?

• A. Redness
• B. Swelling
• C. Fever
• D. Pain

Answer: (B)

During inflammation, inflammatory mediators like histamine increase the permeability of the vascular endothelium. This makes gaps between endothelial cells larger, allowing fluid and plasma proteins to leak from the vessels into the surrounding tissue. The resulting accumulation of fluid in the tissue is edema, which presents as swelling.

Redness and warmth come from vasodilation (more blood flow) rather than from the permeability change itself. Fever is a systemic response driven by pyrogens acting on the hypothalamus, not a local permeability effect. Pain can arise from the edema pressing on nerves and from mediators that sensitize nociceptors, but the direct sign produced by increased permeability is swelling.