Which lamina of Rexed in the spinal cord gray matter is the principal site where nociceptive C-fibers synapse and contains the substantia gelatinosa?
- A Lamina I (marginal zone)
- B Lamina IV
- C Lamina II ✓
- D Lamina IX
Correct answer: C. Lamina II
Explanation
Lamina II of Rexed is the substantia gelatinosa of Rolando, located at the tip of the dorsal horn. It is the primary site for modulation of nociceptive input, where unmyelinated C-fibers (and some Aδ fibers) synapse with interneurons. Endogenous opioid interneurons and enkephalin-containing cells are abundant here, making it the anatomical basis for the gate control theory of pain. Lamina I (marginal zone) also receives pain inputs. Lamina IX houses alpha motor neurons.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.