Cause of vasodilatation in spider nevi
**Core Concept**
Spider nevi, also known as spider angiomas, are a common vascular lesion characterized by a central red spot with radiating dilated blood vessels. The pathophysiology of spider nevi involves vasodilatation of the arterioles, which is caused by a complex interplay of local and systemic factors.
**Why the Correct Answer is Right**
The correct answer is related to the role of nitric oxide (NO) in vasodilatation. NO is a potent vasodilator produced by endothelial cells lining blood vessels. In spider nevi, the increased expression of endothelial nitric oxide synthase (eNOS) leads to elevated levels of NO, causing relaxation of vascular smooth muscle cells and subsequent vasodilatation. This results in the characteristic dilated blood vessels seen in spider nevi.
**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not accurately describe the mechanism of vasodilatation in spider nevi. While prostaglandins may play a role in vasodilatation, they are not the primary cause of vasodilatation in spider nevi.
**Option B:** is incorrect because it is not directly related to the pathophysiology of spider nevi. Although estrogen receptors are present in blood vessels, they are not the primary cause of vasodilatation in spider nevi.
**Option C:** is incorrect because it is a general term that does not accurately describe the specific mechanism of vasodilatation in spider nevi. While various factors can contribute to vasodilatation, the specific role of NO in spider nevi is not accurately captured by this option.
**Clinical Pearl / High-Yield Fact**
Spider nevi are often associated with liver disease, particularly in the context of cirrhosis. This is because the liver is responsible for metabolizing estrogen, and cirrhosis can lead to an accumulation of estrogen, which can contribute to the development of spider nevi.
**Correct Answer:** C. Nitric oxide.