Which two muscles close the lateral pelvic wall?

Which two muscles close the lateral pelvic wall?

• A. Levator ani and coccygeus
• B. Gluteus medius and minimus
• C. Obturator internus and piriformis
• D. Obturator externus and piriformis

Answer: (C)

The boundary that forms the lateral wall of the pelvic cavity is created mainly by two muscles: obturator internus and piriformis. Obturator internus comes from the inner surface of the obturator membrane and surrounding bone, then its tendon exits through the lesser sciatic foramen to insert on the femur; as it crosses the lateral aspect of the pelvis, it shapes the sidewall of the pelvic cavity. Piriformis originates from the anterior sacrum and coccyx, passes through the greater sciatic foramen, and inserts on the greater trochanter, lying along the posterior aspect of the pelvis and contributing to the posterior part of the lateral wall. Together, these two muscles close off the lateral boundary of the pelvis. The pelvic floor muscles (levator ani and coccygeus) form the bottom boundary, and the gluteal muscles lie outside the pelvic cavity; obturator externus is near the lateral wall but does not define it in the same way as the obturator internus.

The boundary that forms the lateral wall of the pelvic cavity is created mainly by two muscles: obturator internus and piriformis. Obturator internus comes from the inner surface of the obturator membrane and surrounding bone, then its tendon exits through the lesser sciatic foramen to insert on the femur; as it crosses the lateral aspect of the pelvis, it shapes the sidewall of the pelvic cavity. Piriformis originates from the anterior sacrum and coccyx, passes through the greater sciatic foramen, and inserts on the greater trochanter, lying along the posterior aspect of the pelvis and contributing to the posterior part of the lateral wall. Together, these two muscles close off the lateral boundary of the pelvis. The pelvic floor muscles (levator ani and coccygeus) form the bottom boundary, and the gluteal muscles lie outside the pelvic cavity; obturator externus is near the lateral wall but does not define it in the same way as the obturator internus.