Which muscles form the lateral margins of the true pelvis surrounding the obturator foramen?

Which muscles form the lateral margins of the true pelvis surrounding the obturator foramen?

• A. Obturator internus
• B. Piriformis
• C. Iliopsoas
• D. Levator ani

Answer: (A)

Obturator internus forms the lateral margins of the true pelvis around the obturator foramen. It begins on the inner surface of the obturator membrane and the surrounding pelvic bones, then passes through the lesser sciatic foramen to reach its insertion on the greater trochanter of the femur. This placement makes it the muscular boundary on the lateral wall where the obturator foramen sits. The piriformis is located more posteriorly as part of the posterior pelvic wall, the iliopsoas runs along the anterior aspect near the pelvic brim, and levator ani makes up the pelvic floor rather than the lateral wall.

Obturator internus forms the lateral margins of the true pelvis around the obturator foramen. It begins on the inner surface of the obturator membrane and the surrounding pelvic bones, then passes through the lesser sciatic foramen to reach its insertion on the greater trochanter of the femur. This placement makes it the muscular boundary on the lateral wall where the obturator foramen sits. The piriformis is located more posteriorly as part of the posterior pelvic wall, the iliopsoas runs along the anterior aspect near the pelvic brim, and levator ani makes up the pelvic floor rather than the lateral wall.