Structure: Components of m. levator ani
The muscle forms a muscular funnel and is structurally divided into three paired parts:
- Pubococcygeus muscle (m. pubococcygeus) — its medial fibers loop around the urogenital hiatus and the structures passing through it (vagina and urethra).
- Iliococcygeus muscle (m. iliococcygeus) — forms the middle part of the levator ani.
- Ischiococcygeus muscle (m. ischiococcygeus, often called the coccygeus) — forms the posterior part of the muscular pelvic floor.
Origin and Insertion
The muscle originates from the inner surface of the inferior pubic ramus and from the tendinous arch of the pelvic fascia (arcus tendineus fasciae pelvis), which is a thickening of the fascia overlying the obturator internus muscle.
Attachment points of the muscular base include:
- Anteriorly: Horizontal ramus of the pubis and the inner surface of the pubic symphysis.
- Laterally: Tendinous arch of the pelvic fascia.
- Posteriorly: Ischial spine.
Topography and Neighboring Structures
The anterior fibers of the muscle participate in supporting and fixing the urinary bladder and vagina.
Clinical Significance: Trauma and Surgery
The condition of the m. levator ani is crucial in obstetrics and gynecology:
- Obstetric perineal tears: A second-degree perineal tear damages the pelvic floor muscles, primarily the m. levator ani. These tears typically occur during the late second stage of labor and may be spontaneous or iatrogenic.
- Pelvic floor reconstruction: In pelvic organ prolapse, colpoperineorrhaphy with levator plication is performed. A key step involves dissecting the posterior vaginal wall mucosa, identifying the m. levator ani fibers, and approximating them with sutures. This restores the musculo-fascial structure of the perineum and pelvic floor. Levator plication is also a component of vaginal hysterectomy and the Manchester procedure.
- Diagnostics: Electromyography (EMG) is indicated for patients suspected of pelvic floor dyssynergia. This method evaluates the viability and functional activity of muscle fibers, as well as the peripheral nerves innervating the anal sphincter mechanism. Diagnostic techniques include bipolar anal electrodes for global bioelectrical activity, segmental electrodes for regional activity, and needle electrodes for detailed evaluation of pelvic floor musculature.