Ligament · Pelvis

Obturator membrane

Membrana obturatoria

A sheet of interlacing fibres closing the large oval hole in the front of the pelvic bone, between the pubis and the ischium. It seals that opening almost completely; the exception is a small gap left at its upper outer corner, which turns the bony obturator groove into the obturator canal and lets the obturator nerve and vessels leave the pelvis for the inner thigh. Both obturator muscles take origin from it — internus from the inner face, externus from the outer — so it is a working attachment sheet in its own right rather than simply a lid over a hole.