Pelvic Anatomy Quiz

Pelvic Bones

• The pelvis is formed by 2 hip bones anteriorly and laterally, and the sacrum and coccyx posteriorly
• The pelvic inlet (brim) is triangular or heart-shaped in males and transversely oval in females
• Boundaries of the pelvic inlet include the promontory and alae of the sacrum, arcuate lines, and pectineal lines
• The pelvic outlet is bounded by the symphysis pubis, tip of the coccyx, ischial tuberosities, ischiopubic rami, and sacrotuberous ligaments

Pelvic Cavity

• The pelvic cavity lies between the inlet and outlet
• It is divided into two parts by the pelvic diaphragm: the pelvis above the diaphragm and the perineum below

Joints and Ligaments of the Pelvis

• Symphysis pubis: a secondary cartilaginous joint between the two pubic bones
  • Ligaments: superior pubic ligament, inferior pubic ligament, anterior pubic ligament, and posterior pubic ligament
• Sacroiliac joint: a strong weight-bearing plane synovial joint between the auricular surfaces of the sacrum and ilium
  • Ligaments: anterior, posterior, and interosseous sacroiliac ligaments
  • Accessory ligaments: sacrotuberous ligament and sacrospinous ligament
• Sacrococcygeal joint: a secondary cartilaginous joint between the last piece of sacrum and first piece of coccyx

Pelvic Muscles

• Muscles of the posterior wall: piriformis
  • Nerve supply: branches from the sacral plexus
  • Action: lateral rotator of the femur at the hip joint
• Muscles of the lateral walls: obturator internus
  • Nerve supply: nerve to obturator internus from the sacral plexus
  • Action: lateral rotator of the femur at the hip joint
• Muscles of the floor: levator ani and coccygeus
  • Levator ani: divided into pubococcygeus and iliococcygeus
    • Pubococcygeus: puborectalis, levator prostatae (in males) or sphincter vaginae (in females), and pubococcygeus proper
    • Iliococcygeus: inserted into the side of the coccyx and the anococcygeal raphe
  • Coccygeus: origin is the tip of the ischial spine

Nerve Supply and Action of Pelvic Muscles

• Levator ani:
  • Nerve supply: perineal branch of S4 and perineal branch of the pudendal nerve
  • Action: supports and maintains the pelvic viscera in position, increases intra-abdominal pressure during straining, and has a sphincter action on the ano-rectal junction; in females, it also serves as a sphincter of the vagina

This quiz covers the anatomy of the pelvis, including the bony pelvis, pelvic joints, ligaments, and muscles. It is designed for students of medicine and anatomy.