The sensory penis: A comprehensive immunohistological and ontogenetic exploration of human penile innervation.

Abstract

Background: Penile sexual sensation relies on intricate neural structures that remain incompletely characterized. Immunohistological insights into their development and organization can enhance understanding of penile neuroanatomy and function, while optimizing surgical outcomes.

Objectives: To elucidate the ontogeny, organization, and immunohistological features of human penile innervation in fetal and adult specimens, primarily focusing on the frenular delta, sensory corpuscles, and related structures to address gaps in anatomical knowledge and inform surgical practices.

Materials and methods: Formalin-fixed, paraffin-embedded tissues from 30 fetal (8-24 weeks) and 14 adult cadaveric penile specimens were analyzed. Routine histological stains and immunohistochemical markers targeting neural structures were applied. Serial sections were examined for histology, neuroanatomical mapping, sensory corpuscle characterization, and neural density assessments.

Results: Fetal penile neurodevelopment exhibited two phases: the pre-corpuscular stage (8-16 weeks), marked by axonal hyperinnervation and exuberant ventral intraepithelial nerve fibers, and the corpuscular stage (17-24 weeks), characterized by Pacinian corpuscle emergence and targeted neural pruning. Adult specimens showed region-specific neural distributions, with heightened densities in the frenular delta. Intracorporeally, sensory corpuscles exhibited a bimodal intraspongiosal distribution, with Pacinians in the bulb and glans. Molecular profiles of sensory corpuscles, including novel immunoreactivities, were comprehensively documented. The preputial dartos and vasculature displayed dense autonomic innervation. A superficial glans tunica albuginea was identified, with implications for neural organization.

Discussion: These findings reveal previously unrecognized transitions during fetal penile neural development and into adulthood, providing a foundation for the neurodevelopmental biology of the human penis and documenting the frenular delta's unique innervation. The characterization of penile neural components and the glans tunica albuginea addresses longstanding anatomical and sexological questions. Our results inform current debates on penile circumcision and neurotomy.

Conclusion: This study provides a comprehensive ontogenetic framework of penile innervation, emphasizing the frenular delta as a specialized center of sexual sensation.