Pelvic Anatomy and Physiology
What you must know
Build a three-layer mental model: (1) the bony and ligamentous frame (pubic symphysis, ischial spines, sacrospinous and sacrotuberous ligaments, arcus tendineus fasciae pelvis); (2) the muscular floor in three layers - superficial perineal muscles, the urogenital diaphragm layer, and the levator ani (pubococcygeus, puborectalis, iliococcygeus) with the coccygeus; (3) the connective-tissue suspensory system - cardinal-uterosacral complex (Level I), paravaginal/arcus tendineus attachments (Level II), and perineal membrane/distal fusion (Level III).
Understand the fascial spaces (retropubic space of Retzius, vesicovaginal, rectovaginal, presacral, paravaginal) because surgical dissection and complication questions live there. Know ureter course relative to the uterine artery ("water under the bridge"), the bladder neck and urethral sphincter mechanism (intrinsic sphincter plus supportive hammock), and pudendal neurovascular anatomy (Alcock canal, ischial spine landmarks).
Traps
Questions love to swap innervation: levator ani is S3–S4 direct branches (not pudendal); external anal sphincter and superficial perineals are pudendal (S2–S4). Another trap is confusing DeLancey levels with specific defects, or naming the arcus tendineus as a muscle. Watch for "which structure attaches to the ischial spine" (sacrospinous ligament, with coccygeus arising from it).
Rule of thumb
Anchor every structure to a palpable landmark: ischial spine = sacrospinous fixation and pudendal block target; pubic symphysis = retropubic trocar danger zone; white line = paravaginal repair plane. If you can place a needle safely, you understand the anatomy.
Worked example: A question asks which nerve is at risk during sacrospinous ligament fixation. The pudendal nerve and vessels run just posterior/inferior to the ischial spine and sacrospinous ligament - so the answer is pudendal neurovascular bundle, not obturator.