Levator ani muscle

Structure: what is m. levator ani composed of?

The muscle forms a distinctive muscular dome and is structurally divided into three paired parts:

• Pubococcygeus muscle (m. pubococcygeus) — its medial muscle bundles encircle the urogenital hiatus as well as the organs passing through it (vagina and urethra).
• Iliococcygeus muscle (m. iliococcygeus) — forms the middle part of the levator ani muscle.
• Ischiococcygeus muscle (m. ischiococcygeus) — forms the posterior part of the muscular dome.

Origin and insertion?

The muscle originates from the internal surface of the inferior ramus of the pubic bone and from the tendinous arch (arcus tendineus fasciae pelvis). This arch is a thickening of the fascia of the obturator internus muscle.

The attachment sites of the muscle bases (using the ischiococcygeus portion as an example) are distributed as follows:

• Anteriorly: horizontal ramus of the pubic bone and internal surface of the pubic symphysis.
• Laterally: tendinous arch.
• Posteriorly: ischium.

Topography and adjacent structures

The anterior parts of the muscle participate in fixing the urinary bladder.

Clinical significance: injuries and surgery

The condition of the m. levator ani is important in obstetrics and gynecology:

• Tears during childbirth: In second-degree perineal tears, the pelvic floor muscles are injured, primarily the levator ani muscle (m. levator ani). Perineal tears occur at the end of the second stage of labor and can be spontaneous or traumatic.
• Pelvic floor repair: For pelvic organ prolapse, colpoperineolevatoroplasty is performed. A key stage of the operation includes separation of the mucosa of the posterior vaginal wall, isolation of the levators (m. levator ani), and placement of sutures to approximate them to each other. The procedure restores the musculo-fascial structure of the perineum and pelvic floor. Colpoperineolevatoroplasty is part of vaginal hysterectomy and is a stage of the Manchester operation.
• Diagnostics: Electromyography is indicated for patients with suspected pelvic floor muscle dyssynergia. The method evaluates the viability and functional activity of muscle fibers, as well as the condition of the peripheral nerves innervating the anal sphincter apparatus. An anal bipolar electrode is used to assess overall bioelectrical activity, a segmental electrode to assess activity by segments, and a needle electrode to evaluate the condition of the pelvic floor muscles.

Class and exam questions

What else to study on this topic

• Pelvic diaphragm and urogenital diaphragm
• Colpoperineolevatoroplasty
• Ischioanal Fossa
• Perineal tears in childbirth

Other topics in the "Anatomical Structures" section

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