Levator Ani

The levator ani is a broad, thin sheet of skeletal muscle that forms the majority of the pelvic diaphragm. It is essential for supporting pelvic organs, maintaining continence, and resisting intra-abdominal pressure. The muscle group spans from the inner surface of the pelvis to the coccyx and walls of pelvic viscera. It is composed of three parts: puborectalis, pubococcygeus, and iliococcygeus. Together, these muscles provide dynamic support for the pelvic floor and play a vital role in defecation, urination, sexual function, and childbirth.

Structure

The levator ani arises from the inner surface of the pelvis and converges posteriorly around the midline structures. It is paired, with each side forming a hemidiaphragm. The two sides meet at a central raphe posterior to the anal canal.

Subdivisions of Levator Ani

Location

The levator ani is located within the lesser pelvis, forming the majority of the pelvic floor. It lies medial to the obturator internus muscle and stretches from the pubic bone anteriorly to the coccyx posteriorly. The urogenital hiatus (for the urethra and vagina) and anal hiatus (for the anal canal) pass through the muscle, allowing passage of pelvic organs while maintaining muscular support.

Function

• Pelvic Organ Support: Maintains the position of the bladder, rectum, uterus, and prostate
• Continence Control: Puborectalis forms a sling around the anorectal junction, helping maintain fecal continence by creating the anorectal angle
• Closure of Pelvic Outlet: Provides a muscular seal to resist downward pressure from the abdominal cavity
• Functional Assistance: Involved in defecation, micturition, sexual function, and parturition

Innervation

• Nerve to levator ani (S3–S4): Primary motor supply
• Inferior rectal branch of pudendal nerve (S2–S4): Also contributes

Relations

Clinical Significance

• Pelvic Floor Dysfunction: Weakness or injury can lead to urinary or fecal incontinence, organ prolapse, and chronic pelvic pain
• Childbirth Injury: Vaginal delivery can stretch or tear pubococcygeus and puborectalis, especially during prolonged or forceful labor
• Levator Ani Syndrome: Characterized by chronic anorectal pain thought to be due to spasm or tension in the levator ani muscles
• Kegel Exercises: Strengthening of the levator ani, especially pubococcygeus, can improve continence and pelvic support
• Surgical Landmark: Important consideration in pelvic surgeries, including hysterectomy, prostatectomy, and rectal procedures