Question

Contraction of endothelial cells, mild endothelial damage, leucocyte mediated endothelial injury and transcytosis across the endothelial cytoplasm are all mechanisms which are observed during the acute inflammatory response. They all are responsible for:

• A. Increased vascular permeability
• B. Phagocytosis
• C. Decreased vascular permeability
• D. Endothelial cell adhesion

Hint:

Acute inflammation hallmark: Redness + Heat + Swelling = Increased vascular permeability. Think: Endothelium becomes “leaky”.

Answer 1

The Correct Option is A

Concept:
Acute inflammation is a protective response involving vascular and cellular changes aimed at eliminating harmful stimuli. One of the hallmark features is increased vascular permeability, which allows plasma proteins and leukocytes to leave the circulation and enter the affected tissue. The mechanisms responsible for increased vascular permeability include:
• Endothelial cell contraction: Creates intercellular gaps, especially in post-capillary venules.
• Endothelial injury: Leads to direct leakage of fluid and proteins.
• Leukocyte-mediated injury: Activated leukocytes release enzymes and free radicals damaging endothelium.
• Transcytosis: Increased vesicular transport of fluids and proteins across endothelial cells.

Step 1: Understanding each mechanism.
All mechanisms listed in the question involve changes in the endothelial lining of blood vessels, which regulate the movement of substances between blood and tissues.

Step 2: Effect of endothelial contraction.
Endothelial contraction increases the size of gaps between cells, allowing fluid and proteins to escape into interstitial spaces.

Step 3: Effect of endothelial damage.
Damage to endothelial cells disrupts the integrity of the vessel wall, causing leakage.

Step 4: Leukocyte-mediated injury.
Leukocytes adhere to endothelium and release toxic substances that increase permeability.

Step 5: Transcytosis.
Enhances vesicle-mediated transport across endothelial cells, increasing movement of plasma components.

Step 6: Conclusion.
Since all these mechanisms lead to increased movement of fluid and proteins out of blood vessels, they collectively result in: \[ \boxed{\text{Increased vascular permeability}} \]