Internal Anal Sphincter Pressure and Male Orgasm Intensity
The internal anal sphincter (IAS) plays a measurable but indirect role in orgasm intensity for males, primarily through its anatomical connection to the bulbocavernosus muscle and pelvic floor contraction patterns during climax.
Physiological Mechanism
The bulbocavernosus muscle (BCM) is anatomically part of the external anal sphincter complex, not the internal sphincter, and this BCM directly contributes to orgasm through compression of the penile bulb and dorsal penile vein during the ejaculatory process. 1
- During male orgasm, pelvic muscle contractions occur in a characteristic pattern starting at approximately 0.6-second intervals, continuing for 10-15 contractions with steadily increasing intervals of about 0.1 second per contraction. 2
- These orgasmic contractions involve the external anal sphincter and associated pelvic floor musculature, with pressure amplitude increasing from the beginning to a maximum at the seventh or eighth contraction. 2
- The IAS itself is primarily under autonomic control with tonic sympathetic excitatory discharge at rest, but this autonomic tone does not directly generate the rhythmic contractions characteristic of orgasm. 3
Clinical Evidence of IAS-Sexual Function Connection
- In 32 men with acute anal fissure (which causes IAS hypertonia), erectile dysfunction occurred in all patients, with pain radiating to the penis and exacerbating during erection and penile thrusting. 1
- Treatment of the anal fissure and normalization of IAS tone resulted in cure of erectile dysfunction in 30/32 acute cases and 19/21 chronic cases, demonstrating that IAS pathology can significantly impact sexual function. 1
- The IAS showed increased resting electromyographic activity in these patients, while bulbocavernosus reflex and external anal sphincter activity remained normal, suggesting the IAS dysfunction indirectly affected sexual response through pain pathways and protective guarding patterns. 1
Autonomic Control Considerations
- The IAS receives sympathetic innervation from the thoracolumbar outflow, and stimulation of presacral sympathetic nerves causes IAS relaxation (mean pressure fall of 59 cmH2O). 4
- At rest, tonic sympathetic discharge maintains IAS tone, but this excitatory effect disappears when the sphincter is relaxed during substantial rectal distension. 3
- There is no tonic parasympathetic discharge affecting IAS tone at rest in healthy males. 3
Clinical Implications
The IAS does not directly generate orgasmic contractions or determine orgasm intensity in the way that the external anal sphincter and bulbocavernosus muscle do. 2, 1
- However, IAS pathology (hypertonia from fissures, post-surgical dysfunction) can create protective pelvic floor guarding patterns that persist and interfere with normal sexual response. 5, 1
- Pain originating from IAS dysfunction radiates to genital structures and is exacerbated during sexual activity, indirectly reducing orgasm quality through pain-mediated inhibition. 1
- The IAS contributes to overall pelvic floor coordination, and when this coordination is disrupted by IAS pathology, sexual dysfunction including altered orgasm can result. 5, 6
Practical Clinical Perspective
- If a patient reports altered orgasm intensity in the context of anorectal pathology, assess for IAS hypertonia through digital rectal examination and consider manometric studies if indicated. 7, 8
- Treatment should target the underlying IAS pathology (topical calcium channel blockers for hypertonia, pelvic floor physical therapy for post-surgical guarding) rather than attempting to directly manipulate IAS pressure for orgasm enhancement. 5, 9
- Pelvic floor physical therapy with internal myofascial release can address the protective guarding patterns that develop secondary to IAS dysfunction and may improve sexual function over 6-12 months. 5