The 22-year-old female patient cried out in agony from the pain of her burst appendix. Which of the following structures contain the neuronal cell bodies of the pain fibers from the appendix?
**Core Concept**
The pain from the appendix is transmitted through visceral afferent fibers, which are part of the autonomic nervous system. These fibers carry pain signals from the abdominal organs to the spinal cord and ultimately to the brain.
**Why the Correct Answer is Right**
The neuronal cell bodies of the pain fibers from the appendix are located in the dorsal root ganglia (DRG) of the spinal cord. The DRG is a cluster of neurons that contain the cell bodies of the sensory neurons, including those that transmit pain from the viscera. The pain fibers from the appendix synapse on these neurons in the DRG, which then transmit the pain signals to the spinal cord and brain. This process is mediated by the release of neurotransmitters such as substance P and calcitonin gene-related peptide (CGRP) from the terminals of the pain fibers.
**Why Each Wrong Option is Incorrect**
* **Option A:** The substantia gelatinosa is a layer of the spinal cord that contains interneurons involved in the processing of pain, but it does not contain the neuronal cell bodies of the pain fibers from the appendix.
* **Option B:** The posterior horn of the spinal cord is involved in the reception and transmission of sensory information, but it does not contain the neuronal cell bodies of the pain fibers from the appendix.
* **Option D:** The brainstem is involved in the processing of pain, but it does not contain the neuronal cell bodies of the pain fibers from the appendix.
**Clinical Pearl / High-Yield Fact**
The pain from the appendix is often referred to the right lower quadrant of the abdomen due to the convergence of visceral afferent fibers from the appendix onto the same spinal segments as the somatic afferent fibers from the skin and muscles of the right lower quadrant.
**Correct Answer: C. Dorsal root ganglia (DRG) of the spinal cord.**