Obturator membrane
Membrana obturatoria
A thin fibrous sheet that closes most of the obturator foramen of the hip bone, leaving a canal at the top through which the obturator nerve and vessels pass.
At a glance
- English
- Obturator membrane
- Latin (TA2)
- Membrana obturatoria
- System
- Ligament
- Region
- Abdomen
- Side
- Paired, left and right
About the obturator membrane
The obturator foramen is the large opening in the hip bone below the acetabulum, bounded by the pubis and ischium. In life it is not an open hole: the obturator membrane stretches across it. This thin, tough sheet of fibrous tissue attaches around almost the whole sharp edge of the foramen and gives a broad surface for muscles to arise from.
Its fibres are gathered into interlacing bundles that run mostly across the opening. At one point the attachment leaves the edge: at the lower lateral corner it fixes slightly inside the rim, on the inner face of the ischial ramus. At the top the membrane does not reach the bone of the obturator groove. Its uppermost bundle stretches between the anterior and posterior obturator tubercles, and the gap left above this free edge, under the groove on the pubis, is the obturator canal.
Through this short canal the obturator nerve, artery and vein pass from the pelvis into the medial compartment of the thigh. The membrane has a muscle on each face: obturator internus arises from its inner, pelvic surface and the surrounding bone, and obturator externus from its outer surface. Both act as lateral rotators of the hip.
The obturator canal is a weak point in the pelvic wall. An obturator hernia, in which a loop of bowel pushes through it, is rare but tends to occur in thin elderly women and may press on the obturator nerve, giving pain along the inner thigh and knee, known as the Howship-Romberg sign.
Attachments and function
- Attaches from
- The sharp rim of the foramen, and at its lower lateral angle the pelvic surface of the ischial ramus.
- Attaches to
- Spans the foramen to the opposite margin; its upper free border runs between the anterior and posterior obturator tubercles.
- Function
- Closes the obturator foramen, forms the floor of the obturator canal and gives origin to the obturator internus and externus muscles.
- Nerve supply
- No notable supply of its own; the obturator nerve passes through the canal above it.
- Blood supply
- Small branches of the obturator artery.
Anthromica
See the obturator membrane where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
