Pelvic Floor Muscle Anatomy and its Contribution to Penile Erection in Olive Baboons

Objective: Despite the number of studies on the contribution of pelvic floor muscles (PFM) to the penile erection process, their significance is still underestimated. The goal of this study was to investigate the role of PFM in the erection process in non-human primates. Materials and Methods: First, we performed an anatomical study of the penile structures in 12 baboon cadavers. Next, we created chronic electrophysiological models of normal erectile function in 25 olive baboons. We implanted electrodes on the cavernous nerves to control penile blood filling and placed other electrodes on the pudendal nerve to stimulate the ischiocavernosus muscles (ICM) contractions after sufficient blood filling, thus simulating both vascular and muscular phases of penile erection. We controlled the intracavernous pressure (ICP) during nerve stimulations and further performed a mathematical analysis of the collected data. Results: We described the main pro-erectile muscle anatomy and its relationship with penile structures in monkeys. During neurostimulation studies, we showed the key role of ICM in achieving full penile rigidity with suprasystolic ICP up to 120-300 mm Hg. We also developed a math model for calculating the pro-erectile muscle's contraction force with high accuracy. Conclusion: In this study, we demonstrated the crucial role of PFM in the penile erection process using the monkey model, supporting the previous studies' data. We consider these results essential for a better, more complex understanding of the penile erection process and the participating structures in each stage. This is essential for further improving and designing novel erectile dysfunction diagnostics and treatment techniques.