The semimembranosus is the most medial of the three hamstring muscles. It is so named, it lies posteromedially in the thigh, deep to the semitendinosus. The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh, its origin is the superolateral aspect of the ischial tuberosity and it inserts on the medial condyle and nearby margin of tibia. It arises by a thick tendon from the upper and outer impression on the ischial tuberosity and medial 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. It is inserted into the horizontal groove on the posterior medial aspect of the medial condyle of the tibia; the semimembranosus is wider and deeper than the semitendinosus. The tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and laterally to be inserted into the posterior lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint.
The muscle overlaps the upper part of the popliteal vessels. The semimembranosus is innervated by the tibial part of the sciatic nerve; the sciatic nerve consists of the anterior divisions of ventral nerve roots from L4 through S3. These nerve roots are part of the larger nerve network–the sacral plexus; the tibial part of the sciatic nerve is responsible for innervation of semitendinosus and the long head of biceps femoris. It may be reduced or absent, or double, arising from the sacrotuberous ligament and giving a slip to the femur or adductor magnus; the semimembranosus helps to flex the knee joint. It helps to medially rotate the knee: the tibia medially rotates on the femur when the knee is flexed, it medially rotates the femur. The muscle can aid in counteracting the forward bending at the hip joint. Semitendinosus Biceps femoris This article incorporates text in the public domain from page 479 of the 20th edition of Gray's Anatomy Anatomy photo:14:st-0408 at the SUNY Downstate Medical Center Anatomy figure: 14:01-07 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles of the posterior compartment of the thigh."
Anatomy figure: 14:02-06 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles that form the superficial boundaries of the popliteal fossa." Knee/surface/surface4 at the Dartmouth Medical School's Department of Anatomy PTCentral
The gracilis muscle is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above and tapering below, it arises by a thin aponeurosis from the anterior margins of the lower half of the symphysis pubis and the upper half of the pubic arch. The muscle's fibers run vertically downward; this tendon passes behind the medial condyle of the femur, curves around the medial condyle of the tibia where it becomes flattened, inserts into the upper part of the medial surface of the body of the tibia, below the condyle. For this reason, the muscle is a lower limb adductor. At its insertion the tendon is situated above that of the semitendinosus muscle, its upper edge is overlapped by the tendon of the sartorius muscle, which it joins to form the pes anserinus; the pes anserinus is separated from the medial collateral ligament of the knee-joint by a bursa. A few of the fibers of the lower part of the tendon are prolonged into the deep fascia of the leg. By its inner or superficial surface gracilis is in relation with the fascia lata, below with the sartorius and internal saphenous nerve.
By its outer or deep surface with the adductor longus and magnus, the internal lateral ligament of the knee-joint, from which it is separated by a synovial bursa common to the tendons of the gracilis and semitendinosus. The obturator nerve innervates the gracilis muscle via the lumbar spinal vertebrae; the muscle adducts, medially rotates, laterally rotates, flexes the hip as above, aids in flexion of the knee. The gracilis muscle is used as a flap in microsurgery. According to the classification of Mathes and Nahai, it presents a type II blood supply, allowing it to be transferred on its artery derived from the medial circumflex femoral artery; this artery enters the muscle about 10 cm from the pubic symphysis. At this point the nerve enters. Gracilis muscle is used in reconstructive surgery, either as a pedicled flap or as a free microsurgical flap. Both pedicled and free flaps can be musculocutaneos; as a pedicled flap, gracilis muscle can be used in perineal and vaginal reconstruction, after oncological surgery, in the treatment of recurrent anovaginal and rectovaginal fistulas as well in the coverage of the neurovascular bundle after vascular surgery.
As a functioning pedicled flap, the gracilis muscle can be transferred for the treatment of anal incontinence. This technique called graciloplasty was described in the 1950s by Pickrell and was revolutionized in the late 1980s by the introduction of chronic muscle electro-stimulation; the gracilis microsurgical free flap is used in the reconstruction of upper and lower limbs, in breast reconstruction and – as a free functioning flap – to restore forearm function or in dynamic reconstruction of facial paralysis. Gracilis Muscles Clinical Role The muscle may be split to reduce bulk for facial reanimation, as well as to repair hand muscles, it can be used to fashion an external anal sphincter. This article incorporates text in the public domain from page 471 of the 20th edition of Gray's Anatomy Anatomy figure: 12:02-07 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles of the anterior compartment of the thigh." Anatomy figure: 14:02-02 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles that form the superficial boundaries of the popliteal fossa."
Cross section image: pembody/body18b—Plastination Laboratory at the Medical University of Vienna
Tibialis posterior muscle
The tibialis posterior is the most central of all the leg muscles, is located in the deep posterior compartment of the leg. It is the key stabilizing muscle of the lower leg. Blood is supplied to the muscle by the posterior tibial artery, innervation is via the tibial nerve; the tibialis posterior muscle originates on the inner posterior borders of the fibula. It is attached to the interosseous membrane, which attaches to the tibia and fibula; the tendon of the tibialis posterior muscle descends posterior to the medial malleolus and terminates by dividing into plantar and recurrent components. The main portion inserts into the tuberosity of the navicular and the plantar surface of the medial cuneiform; the plantar portion inserts into the bases of the second and fourth metatarsals, the intermediate and lateral cuneiforms and the cuboid. The recurrent portion inserts into the sustentaculum tali of the calcaneus; as well as being a key muscle and tendon for stabilization, the tibialis posterior contracts to produce inversion and assists in the plantar flexion of the foot at the ankle.
The tibialis posterior has a major role in supporting the medial arch of the foot. Dysfunction of the tibialis posterior, including rupture of the tibialis posterior tendon, can lead to flat feet in adults, as well as a valgus deformity due to unopposed eversion when inversion is lost. Anatomy photo:15:st-0416 at the SUNY Downstate Medical Center Diagram at washington.edu Diagram at latrobe.edu.au
Internal obturator muscle
The internal obturator muscle or obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, the rim of the pubis. It exits the pelvic cavity through the lesser sciatic foramen; the internal obturator is situated within the lesser pelvis, at the back of the hip-joint. It functions to help laterally rotate femur with hip extension and abduct femur with hip flexion, as well as to steady the femoral head in the acetabulum, it arises from the inner surface of the antero-lateral wall of the pelvis, where it surrounds the greater part of the obturator foramen, being attached to the inferior pubic ramus and ischium, at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front. It arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, to a slight extent from the obturator fascia, which covers the muscle.
The fibers converge toward the lesser sciatic foramen, end in four or five tendinous bands, which are found on the deep surface of the muscle. The tendon inserts on the greater trochanter of the proximal femur; the internal obturator muscle is innervated by the nerve to internal obturator. This bony surface is covered by smooth cartilage, separated from the tendon by a bursa, 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, 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 and elongated in form, is found between the tendon and the capsule of the hip-joint; this article incorporates text in the public domain from page 477 of the 20th edition of Gray's Anatomy Anatomy photo:13:st-0407 at the SUNY Downstate Medical Center - "Gluteal Region: Muscles" Anatomy photo:43:st-0603 at the SUNY Downstate Medical Center - "The Female Pelvis: Muscles" Cross section image: pelvis/pelvis-e12-15—Plastination Laboratory at the Medical University of Vienna pelvis at The Anatomy Lesson by Wesley Norman perineum at The Anatomy Lesson by Wesley Norman Int.
J. Morphol. 25:95-98, 2007
The iliacus is a flat, triangular muscle which fills the iliac fossa. It forms the lateral portion of iliopsoas, providing flexion of the thigh and lower limb at the acetabulofemoral joint; the iliacus arises from the iliac fossa on the interior side of the hip bone, from the region of the anterior inferior iliac spine. It joins the psoas major to form the Iliopsoas as which it proceeds across the iliopubic eminence through the muscular lacuna to its insertion on the lesser trochanter of the femur, its fibers are inserted in front of those of the psoas major and extend distally over the lesser trochanter. The iliopsoas is innervated by direct branches from the lumbar plexus. In open-chain exercises, as part of the iliopsoas, the iliacus is important for lifting the femur forward. In closed-chain exercises, the iliopsoas bends the trunk forward and can lift the trunk from a lying posture because the psoas major crosses several vertebral joints and the sacroiliac joint. From its origin in the lesser pelvis the iliacus acts on the hip joint.
Platzer, Werner. Color Atlas of Human Anatomy, Vol. 1: Locomotor System. Thieme. ISBN 3-13-533305-1. Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. 2006. ISBN 1-58890-419-9. PTCentral Anatomy figure: 40:07-05 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles and nerves of the posterior abdominal wall." Pelvis at The Anatomy Lesson by Wesley Norman
Adductor longus muscle
In the human body, the adductor longus is a skeletal muscle located in the thigh. One of the adductor muscles of the hip, its main function is to adduct the thigh and it is innervated by the obturator nerve, it forms the medial wall of the femoral triangle. The adductor longus arises from the superior ramus of the pubis, it lies ventrally on the adductor magnus, near the femur, the adductor brevis is interposed between these two muscles. Distally, the fibers of the adductor longus extend into the adductor canal, it is inserted into the middle third of the medial lip of the linea aspera. The adductor longus is in relation by its anterior surface with the pubic portion of the fascia lata, near its insertion with the femoral artery and vein. By its posterior surface with the adductor brevis and magnus, the anterior branches of the obturator artery and nerves, near its insertion with the profunda artery and vein. By its outer border with the pectineus, by the inner border with the gracilis, its main actions is to laterally rotate the thigh.
As part of the medial compartment of the thigh, the adductor longus is innervated by the anterior division of the obturator nerve. The obturator nerve exits via the anterior rami of the spinal cord from L2, L3, L4. Adductor longus is derived from the myotome of spinal roots L2, L3, L4. Cross section image: pembody/body18b—Plastination Laboratory at the Medical University of Vienna Cross section image: pelvis/pelvis-e12-15—Plastination Laboratory at the Medical University of Vienna PTCentral
Quadratus femoris muscle
The quadratus femoris is a flat, quadrilateral skeletal muscle. Located on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, but acts to stabilize the femoral head in the acetabulum, it originates on the lateral border of the ischial tuberosity of the ischium of the pelvis. From there, it passes laterally to its insertion on the posterior side of the head of the femur: the quadrate tubercle on the intertrochanteric crest and along the quadrate line, the vertical line which runs downward to bisect the lesser trochanter on the medial side of the femur. Along its course, quadratus is aligned edge to edge with the inferior gemellus above and the adductor magnus below, so that its upper and lower borders run horizontal and parallel. At its origin, the upper margin of the adductor magnus is separated from it by the terminal branches of the medial femoral circumflex vessels. A bursa is found between the front of this muscle and the lesser trochanter. Sometimes absent.
Groin pain can be a disabling ailment with many potential root causes: one such cause overlooked, is quadratus femoris tendinitis. Magnetic resonance imaging can show abnormal signal intensity at the insertion of the right quadratus femoris tendon, which suggests inflammation of the area. Since the muscle works to laterally rotate and adduct the femur, actions involving the lower body can strain the muscle. In addition, patients present with hip pain and an increased signal intensity of the MRI of the quadratus femoris have been shown to have a narrower ischiofemoral space compared to the general populace; the ischiofemoral impingement may be a cause of the hip pain associated with quadratus femoris tendinitis. This article incorporates text in the public domain from page 477 of the 20th edition of Gray's Anatomy Mcminn, R. M. H.. Last's Applied. Elsevier Australia. ISBN 0-7295-3752-8. Platzer, Werner. Color Atlas of Human Anatomy, Vol 1: Locomotor system. Thieme. ISBN 3-13-533305-1. Thieme Atlas of Anatomy.
Thieme. 2006. ISBN 978-1-60406-062-1. PTCentral Anatomy photo:13:st-0409 at the SUNY Downstate Medical Center