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Acute Inflammation Quiz
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Which of the following best explains why an acutely inflamed area looks red and feels warm?
- A Dilation of superficial veins causing blood to pool in the area You picked ✕
- B Leakage of protein-rich fluid into the interstitial space You picked ✕
- C Release of pyrogens that act on the hypothalamus to raise the core temperature You picked ✕
- D Increased local blood flow due to arteriolar vasodilation You picked ✓
- E Increased metabolic heat production by local tissue cells You picked ✕
Correct!
Incorrect
The answer is D: Increased local blood flow due to arteriolar vasodilation
Explanation
Why D is correct
See Clinical Signs of Inflammation. Option D is correct because the redness and warmth of acute inflammation come from vasodilation of the arterioles (the smallest arteries, which control blood flow into the capillaries). Chemical messengers called mediators, such as histamine, relax the smooth muscle in the vessel walls, so the vessels widen and more blood flows in. More blood near the surface looks red (rubor, the Latin word for redness) and, because blood comes from the warm core of the body, the area feels warm (calor, heat). The other classic signs have their own causes: increased vessel permeability causes swelling, and mediators acting on nerve endings cause pain, with loss of function sometimes added as a fifth sign. Memory aid: heat and redness mean more blood flowing in; swelling means fluid leaking out; pain means nerve endings stimulated.
- Cause: mediators such as histamine cause arteriolar vasodilation, so more blood flows in.
- Redness: more blood near the surface looks red (rubor).
- Warmth: blood from the warm core makes the area feel warm (calor).
Why the other options are incorrect
- A. Dilation of superficial veins causing blood to pool in the area: Venous pooling can occur with inflammation but is a result of the increased blood flow, and the characteristic bright red and warm appearance is due to arteriolar dilation. Pooling of venous blood would tend to make the area dusky or cool rather than warm. Your answer
- B. Leakage of protein-rich fluid into the interstitial space: Increased capillary permeability is the mechanism of inflammatory swelling, not of redness and warmth. Fluid exudation does not bring more blood into the area, so it does not directly produce rubor and calor. Your answer
- C. Release of pyrogens that act on the hypothalamus to raise the core temperature: Pyrogens act on the hypothalamus to cause fever, which is a systemic response. They do not produce the local redness and warmth of a single inflamed area, which depends on the local circulation. Your answer
- E. Increased metabolic heat production by local tissue cells: Metabolism in the inflamed tissue makes only a negligible contribution to the heat. The warmth comes from the increased delivery of warm blood; if local metabolism were the main source, the area would not be flushed in the way seen in acute inflammation. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which step allows neutrophils to cross the vessel wall and its basement membrane to enter inflamed tissue?
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2
Which change at the level of the small blood vessels most directly leads to the formation of an inflammatory exudate rather than a transudate?
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