Semimembranosus muscle
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| Semimembranosus muscle | ||
|---|---|---|
| Muscles of the gluteal and posterior femoral regions. Semimembranosus labeled at bottom left. | ||
 | ||
| Semimembranosus labeled at bottom right. | ||
| Latin | musculus semimembranosus | |
| Gray's | subject #128 479 | |
| Origin: | Ischial tuberosity | |
| Insertion: | Medial surface of tibia | |
| Artery: | profunda femoris, gluteal artery | |
| Nerve: | sciatic nerve | |
| Action: | Hip extension, Knee flexion | |
| Antagonist: | Quadriceps muscle | |
| Dorlands/Elsevier | m_22/12550673 | |
The semimembranosus is a muscle in the back of the thigh. It is the most medial of the three hamstring muscles.
Structure
The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh.
It arises by a thick tendon from the upper and outer impression on the tuberosity of the ischium, above and lateral to the biceps femoris and semitendinosus.
The tendon of origin expands into an aponeurosis, which covers the upper part of the anterior surface of the muscle; from this aponeurosis muscular fibers arise, and converge to another aponeurosis which covers the lower part of the posterior surface of the muscle and contracts into the tendon of insertion.
It is inserted mainly into the horizontal groove on the posterior medial aspect of the medial condyle of the tibia.
The tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and lateralward to be inserted into the back part of the lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint; a second is continued downward to the fascia which covers the Popliteus muscle; while a few fibers join the tibial collateral ligament of the joint and the fascia of the leg.
The muscle overlaps the upper part of the popliteal vessels.
Innervation
The semimembranosus is innervated by the tibial part of the sciatic nerve.
Actions
The semimembranosus helps to extend (straighten) the hip joint and flex (bend) the knee joint. It also helps medially rotate the knee.
Variations
It may be reduced or absent, or double, arising mainly from the sacrotuberous ligament and giving a slip to the femur or adductor magnus.
Additional images
 Right hip bone. External surface. |
 Bones of the right leg. Posterior surface. |
 The popliteal, posterior tibial, and peroneal arteries. |
 Back of left lower extremity. |
See also
External links
- LUC semm
- SUNY Labs 14:st-0408
- SUNY Figs 14:01-07 - "Muscles (hamstrings) of the posterior compartment of the thigh."
- SUNY Figs 14:02-06 - "Muscles that form the superficial boundaries of the popliteal fossa."
- Anatomy at Dartmouth knee/surface/surface4
- PTCentral
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
de:Musculus semimembranosusfr:Muscle semi-membraneux he:השריר החצי קרומי
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
