International Urology and Nephrology

, Volume 39, Issue 2, pp 541–546 | Cite as

The effect of external urethral sphincter contraction on the cavernosus muscles and its role in the sexual act

  • Ahmed ShafikEmail author
  • Ismail A. Shafik
  • Olfat El Sibai
  • Ali A. Shafik
Original Paper



A study of the effect of external urethral sphincter contraction on ischio-/bulbo-cavernosus muscles could not be traced in the literature. We investigated the hypothesis that external urethral sphincter contraction induces cavernosus muscles’ contraction.


Twenty-one healthy volunteers (age 37.6 ± 9.7 SD years, 12 men, nine women) were studied. The electromyographic response of the ischio- and bulbo-cavernosus muscles to external urethral sphincter stimulation was recorded before and after anesthetization of the external urethral sphincter, and the ischio- and bulbo-cavernosus muscles; the response was also recorded using normal saline instead of lidocaine.


Upon external urethral sphincter stimulation (five square pulses, 1 ms duration, 53.8 ± 10.2 mA threshold), both cavernosus muscles exhibited increased electromyographic activity with a mean amplitude of 386.2 ± 44.9 μV for the ischio-cavernosus and 318.4 ± 36.6 μV for the bulbo-cavernosus muscle. The mean latency read 16.8 ± 1.3 ms for the ischio-cavernosus muscle and 15.7 ± 1.2 ms for the bulbo-cavernosus muscle. Neither the ischio- nor the bulbo-cavernosus muscle responded to stimulation of the anesthetized external urethral sphincter, but both responded after saline administration. Likewise, the anesthetized ischio- and bulbo-cavernosus muscles showed no response to external urethral sphincter stimulation but responded after saline had been injected.


Increased electromyographic activity of the two cavernosus muscles on external urethral sphincter stimulation presumably denotes contraction of these two muscles and that this action is probably reflex, mediated through the ‘sphinctero-cavernosus-reflex’. Cavernosus muscles’ contraction assists in the erectile and ejaculatory mechanisms. It is suggested that this reflex be included as an investigative tool in the diagnosis of erectile and ejaculatory disorders, provided further studies are performed.


Ejaculation Erection  Micturition Sexual intercourse 



External urethral sphincter


Ischio-/bulbo-cavernosus muscles




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Margot Yehia assisted in preparing the manuscript.


  1. 1.
    Harti BI (1997) The action of extrinsic penile muscles during copulation in the male dog. Anat Rec 173:1–6CrossRefGoogle Scholar
  2. 2.
    Newman Hf, Northhup JD (1981) Mechanism of human penile erection: an overview. Urology 17: 399–408PubMedCrossRefGoogle Scholar
  3. 3.
    Lue Tf et al (1994) Physiology of erectile function and dysfunction. Campbell’s Urol Update 12:1–10Google Scholar
  4. 4.
    Anderson KE, Wagner G (1995) Physiology of penile erection. Physiol Rev 75:191–202Google Scholar
  5. 5.
    Shafik A (1993) The cervicocavernosus reflex: description of the reflex and its role in the sexual act. Int Urogynecol J 4:70–73CrossRefGoogle Scholar
  6. 6.
    Shafik A (1993) Vaginocavernosus reflex. Clinical significance and role in sexual act. Gynecol Obstet Invest 35:114–117PubMedCrossRefGoogle Scholar
  7. 7.
    Fournier GR Jr et al (1987) Mechanism of venous occlusion during penile erection: anatomic demonstration. J Urol 137:163–166PubMedGoogle Scholar
  8. 8.
    Azadzoi Km et al (1995) Hemodynamics of penile erection. III. Measurement of deep intracavernosal and subtunical blood flow and oxygen tension. J Urol 153:521–526PubMedCrossRefGoogle Scholar
  9. 9.
    De Groat WC, Booth AM (1993) Neural control of penile erection. In: Maggi CA (ed.), The autonomic nervous system. Nervous control of the urogenital system. Harwood, London, pp 465–513Google Scholar
  10. 10.
    Paick JS et al (1993) Anatomy of cavernosus nerves distal to prostate: microdissection study in adult male cadavers. Urology 42:45–149CrossRefGoogle Scholar
  11. 11.
    Burnett AL et al (1993) Immunohistochemical localization of nitric oxide synthesis in the autonomic innervation of the human penis. J Urol 50:73–76Google Scholar
  12. 12.
    Giuliano F, Rampin O (2000) Central neural regulation of penile erection. Neurosci Biobehav Rev 24:561–569CrossRefGoogle Scholar
  13. 13.
    Mallick Hn et al (1994) Sensory modulation of the medial preoptic area neuronal activity by dorsal penile nerve stimulation in rats. J Urol 151:759–762PubMedGoogle Scholar
  14. 14.
    Giuliano F et al (1993) Electrophysiologic study of relations between the dorsal nerve of the penis and the lumbar sympathetic chain in the rat. J Urol 150:1960–1964PubMedGoogle Scholar
  15. 15.
    Goldstein M (1998) Surgical management of male infertility and other scrotal disorders. In: Walsh PC, Retik AB, Vanghan ED Jr, Wein AJ (eds), Campbell’s urology, 7th edn. WB Saunders Co, Philadelphia, pp 1331–1377Google Scholar
  16. 16.
    Warwick R, Williams PL (1975) Myology. In: Warwick R, Williams PL (eds), Gray’s anatomy, 35th edn, Longman, London, pp 474–585Google Scholar
  17. 17.
    Wood PA (1985) Anatomy of the anal sphincters and plevic floor. In: Henry MM, Swash M (eds) Coloproctology and the pelvic floor: pathophysiology and management, 1st edn. London, pp 3–21Google Scholar
  18. 18.
    Yokoyama O et al (2000) Diagnostic value of intravesical lidocaine for overactive bladder. J Urol 164:340–344PubMedCrossRefGoogle Scholar
  19. 19.
    Silva C et al (2002) The effect of intravesical resininferatoxin in patients with idiopathic detrusor instability suggests that involuntary detrusor contractions are triggered by C-fiber input. J Urol 168:575–579PubMedCrossRefGoogle Scholar
  20. 20.
    Shafik A, El-Sibai O (2001) Effect of vaginal distension on the vesicourethral function with identification of vagino-vesicourethral reflex. J Urol 165:887–889Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Ahmed Shafik
    • 1
    Email author
  • Ismail A. Shafik
    • 1
  • Olfat El Sibai
    • 2
  • Ali A. Shafik
    • 1
  1. 1.Department of Surgery and Experimental Research, Faculty of MedicineCairo UniversityCairoEgypt
  2. 2.Department of Surgery, Faculty of MedicineMenoufia UniversityShebin El-KomEgypt

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