Internal obturator muscle

Structure

Origin

The internal obturator muscle arises from the inner surface of the antero-lateral wall of the pelvis. It surrounds the obturator foramen. It is attached to the inferior pubic ramus and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim. It reaches from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.

It also arises from the pelvic surface of the obturator membrane. This is except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle.

Passage

The fibers converge through the lesser sciatic foramen. These end in four or five tendinous bands, which are found on the deep surface of the muscle. These bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity.

The obturator nerve passes on the superficial surface of the internal obturator muscle. The pudendal nerve passes on the lateral surface of the internal obturator muscle and the coccygeus muscle. The sciatic nerve passes superficial to the internal obturator muscle on the posterior surface.

Insertion

The tendon inserts on the greater trochanter of the proximal femur.

Nerve supply

The internal obturator muscle is supplied by the obturator internus nerve (L5, S1, and S2).

Bursa/bands

This bony surface is covered by smooth cartilage, which is separated from the tendon by a bursa, and presents one or more ridges corresponding with the furrows between the tendinous bands.

These bands leave the pelvis through the lesser sciatic foramen and unite into a single flattened tendon, which passes horizontally across the capsule of the hip-joint, and, after receiving the attachments of the superior and inferior gemellus muscles, is inserted into the forepart of the medial surface of the greater trochanter above the trochanteric fossa.

A bursa, narrow and elongated in form, is usually found between the tendon and the capsule of the hip-joint. It occasionally communicates with the bursa between the tendon and the ischium.

Function

The internal obturator muscle helps to support the urinary bladder as part of the pelvic floor.

Additional images

File:Obturator internus muscle.jpg|Obturator internus muscle File:Slide10A.JPG|Obturator internus muscle File:Braus 1921 251.png|"Triceps coxae"

References

References

1. (2018-01-01). "Chapter 2 - Abdominal and Pelvic Anatomy". Elsevier.
2. Jacob, S.. (2008-01-01). "Chapter 4 - Abdomen". Churchill Livingstone.
3. (2015-01-01). "Chapter 35 - Injuries to the Nerves of the Abdominopelvic Region". Academic Press.
4. (2015-01-01). "Chapter 5 - Anatomy and physiology of the lower urinary tract". Elsevier.
5. Midha, Rajiv. (2008-01-01). "2 - Mechanisms and pathology of injury". W.B. Saunders.
6. Bouche, P.. (2013-01-01). "Chapter 19 - Compression and entrapment neuropathies". Elsevier.
7. Richenberg, Jonathan L.. (2011-01-01). "CHAPTER 29 - Ultrasound of the bladder". Churchill Livingstone.