make a chart of pelvic floor muscles including muscle, origin, insertion, action, innervation and group
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I now have comprehensive data from three authoritative textbooks. I also note the THIEME Atlas has the Coccygeus origin/insertion reversed from other sources (ischial spine = origin, sacrum = insertion is the correct anatomy). Let me compile the full chart now.
Pelvic Floor Muscles: Complete Anatomical Chart
Sources: Gray's Anatomy for Students (Table 5.2), THIEME Atlas of Anatomy: General Anatomy and Musculoskeletal System (Section 2.10), Berek & Novak's Gynecology (Table 5-2), Campbell-Walsh-Wein Urology
Group I - Pelvic Diaphragm
| Muscle | Origin | Insertion | Action | Innervation | Group |
|---|---|---|---|---|---|
| Levator ani (overall) | Tendinous arch (thickening of obturator internus fascia), posterior body of pubis to ischial spine | Perineal body, wall of anal canal, anococcygeal ligament, coccyx (varies by part) | Supports pelvic viscera; maintains anorectal angle; reinforces external anal sphincter; acts as vaginal sphincter in females | Branches from anterior ramus of S4; inferior rectal branch of pudendal nerve (S2-S4) | Pelvic Diaphragm |
| - Puborectalis | Superior pubic ramus, both sides of pubic symphysis | Loops around anorectal junction; interwoven with deep external anal sphincter (U-shaped sling) | Maintains anorectal angle; aids fecal continence | Pudendal nerve and direct branches of sacral plexus (S2-S4) | Pelvic Diaphragm (Levator ani) |
| - Pubococcygeus | Posterior portion of pubis and tendinous arch (lateral to puborectalis origin) | Anococcygeal ligament, coccyx; forms pubovaginal sling around vagina/urethra | Supports pelvic viscera; visceral control via pubovaginal sling around vagina and urethra | Pudendal nerve (S2-S4) | Pelvic Diaphragm (Levator ani) |
| - Iliococcygeus | Tendinous arch of obturator internus fascia (posterior part) and ischial spine | Iliococcygeal raphe, anococcygeal ligament, coccyx | Supports pelvic viscera; holds pelvic organs in place | Pudendal nerve (S2-S4) | Pelvic Diaphragm (Levator ani) |
| Coccygeus | Ischial spine and pelvic surface of the sacrospinous ligament | Lateral margin of coccyx and lower sacrum (S4-S5) | Supports pelvic floor; flexes/pulls coccyx anteriorly after defecation | Branches from anterior rami of S3-S5 (direct sacral plexus branches) | Pelvic Diaphragm |
Group II - Urogenital Diaphragm (Deep Perineal Pouch)
| Muscle | Origin | Insertion | Action | Innervation | Group |
|---|---|---|---|---|---|
| Deep transverse perineal | Medial aspect of ischiopubic rami / inferior pubic ramus | Lower vaginal wall; anterior fibers blend with external urethral sphincter; blends at perineal body | Stabilizes perineal body; supports urogenital structures; closes urethra | Pudendal nerve (S2-S4) | Urogenital Diaphragm |
| External urethral sphincter | Inferior pubic ramus (outer striated part = omega-shaped; inner ring = smooth muscle) | Encircles urethra | Closes and controls the urethra (voluntary) | Pudendal nerve (S2-S4) | Urogenital Diaphragm |
Group III - Superficial Perineal Muscles
| Muscle | Origin | Insertion | Action | Innervation | Group |
|---|---|---|---|---|---|
| Superficial transverse perineal | Ischial ramus (ischial tuberosity) | Perineal body (central perineal tendon) | Stabilizes perineal body; holds pelvic organs in place | Pudendal nerve (S2-S4) | Superficial Perineal |
| Bulbospongiosus | Perineal body (anteriorly to clitoris in females; to penile raphe in males) | Clitoris/dorsal surface (females); corpus spongiosum (males) | Narrows vaginal introitus (females); compresses corpus spongiosum (males); aids erection/ejaculation | Pudendal nerve (S2-S4) | Superficial Perineal |
| Ischiocavernosus | Ischial ramus | Crus of penis or clitoris | Compresses crura; maintains erection by impeding venous outflow | Pudendal nerve (S2-S4) | Superficial Perineal |
| External anal sphincter | Perineal body (anteriorly), encircles anal canal to anococcygeal ligament (posteriorly) | Circular around anal canal; divided into subcutaneous, superficial, and deep parts | Closes the anus (voluntary continence) | Pudendal nerve (S2-S4); inferior rectal nerve | Superficial Perineal |
Group IV - Lateral Pelvic Wall Muscles (contribute to pelvic support)
| Muscle | Origin | Insertion | Action | Innervation | Group |
|---|---|---|---|---|---|
| Obturator internus | Superior and inferior pubic rami; obturator membrane | Greater trochanter of the femur | Lateral rotation of thigh; assists in stabilizing femoral head; forms lateral pelvic wall | Obturator internus nerve (L5-S1) | Lateral Pelvic Wall |
| Piriformis | Anterior aspect of S2-S4 sacral segments; sacrotuberous ligament | Greater trochanter of the femur | Lateral rotation and abduction of thigh in flexion; holds femoral head in acetabulum; forms muscular bed for sacral plexus | S1-S2 (direct sacral plexus branches) | Lateral Pelvic Wall |
Key Points
- All pelvic diaphragm and perineal muscles are innervated by the pudendal nerve (S2-S4), with the coccygeus receiving additional direct sacral plexus input (S3-S5).
- The levator ani nerve (from S3-S4-S5, traveling medial to the ischial spine) is now recognized as the primary innervation to the levator ani complex - distinct from the pudendal nerve which innervates it from below.
- The perineal body (central perineal tendon) is the keystone structure where bulbospongiosus, superficial/deep transverse perineal, and external anal sphincter converge.
- The tendinous arch of the levator ani (ATLA) is the fascial condensation over obturator internus from which puborectalis, pubococcygeus, and iliococcygeus originate.
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