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Muscles of the Lower Extremity

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Terms

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Inferior Extensor Retinaculum
Y-shaped band on anterior surface of ankle that retains anterior crural muscle tendons. Upper crus attaches to medial malleolus. Lower crus blends with fascia on medial side of foot. Stem begins on lateral side of foot.
Flexor Retinaculum
Fibrous band on medial side of ankle. Holds tendons for flexor hallucis longus, flexor digitorum longus, & tibialis posterior. Run from medial malleolus to tarsal bones.
Fascia Lata
Strong fascia enveloping muscles of the thigh.
Quadratus Lumborum
O & I: Attached superiorly to 12th rib, medially to transverse process of lumbar vertebrae, & inferiorly to posterior edge of iliac crest.
N: Subcostal nerve & branches of lumbar plexus.
A: Lateral flexion of trunk.
Levator Ani

[model only]
O: Pubis, pelvic fascia, ischial spine.
I: Central tendon of perineum, external anal sphincter, sacrum, & coccyx.
N: Pudendal nerve.
A: Supports pelvic contents, draws anus upward, and [females] constricts vagina.
Plantar Aponeurosis
Longitudinally arranged bands of white fibrous connective tissue. Radiates toward toes from medial process of the tuberosity of the calcaneus.
Coccygeus

[model only]
O: Ischial spine.
I: Sacrum & coccyx.
N: Pudendal nerve.
A: Supports pelvic contents & draws coccyx forward.
Transversus Perinei Superficialis

[model only]
O: Ramus of ischium.
I: Perineal body.
N: Pudendal nerve.
A: Draws back perineal body.
Bulbospongiosus
Male & Female
[model only]
O: Perineal body (& in males the median raphe).
I: [FEMALE] Corpora cavernosa of the clitoris.
[MALE] Urogenital diaphragm, corpora cavernosa, & corpus spongiosum of penis.
N: Pudendal nerve.
A: [Females] Vaginal sphincter & erection of clitoris.
[Males] Assists in erection, ejaculation, and micturition.
Ischiocavernosus

[model only]
O: Ramus of ischium.
I: [FEMALE] Corpus cavernosum of clitoris.
I: [MALE] Corpus cavernosum of penis.
N: Pudendal nerve.
A: Compresses spongy erectile tissue of corpus cavernosum to maintain erection of tissue.
Transversus Perinei Profundus

[model only]
O: Ramus of ischium.
I: Median raphe with opposite muscle.
N: Pudendal nerve.
A: Compression of urethra.
Spinchter Urethrae

[model only]
O: Inferior ramus of pubis.
I: Midline raphe anterior & posterior to membranous urethra.
N: Pudendal nerve.
a: Constricts membranous urethra.
Iliopsoas
Compound muscle & chief flexor of the thigh.

= Union of Iliacus & Psoas Major.
Psoas Major
O: Bodies of vertebrae and intervertebral disks from T12 to L5.
I: Lesser trochanter of femur.
N: Lumbar plexus.
A: lateral flexor of vertebral column, chief flexor of the thigh, & lateral rotator of thigh.
Iliacus
O: Iliac fossa.
I: Lesser trochanter of femur.
N: Femoral nerve.
A: Flexes thigh & rotates laterally.
Psoas Minor
O: Bodies of T12 and L1 vertebrae and intervertebral disk between them.
I: Iliopubic eminence & pectineal line of pubis.
N: Branch of spinal nerve L1.
A: Flexes vertebral column or pelvis.
Gluteus Maximus
O: Ilium behind posterior gluteal line, sacrum, coccyx, & sacrotuberous ligament.
I: Iliotibial tract of fascia lata and gluteal tuberosity of femur.
N: Inferior gluteal nerve.
A: Extends thigh, rotates thigh laterally, & abducts thigh.
Gluteus Medius
O: Ilium between anterior & posterior gluteal lines.
I: Outer surface of greater trochanter.
N: Superior gluteal nerve.
A: abducts & medially rotates thigh.
Gluteus Minimus
O: Ilium between anterior and inferior gluteal lines.
I: Anterior surface of greater trochanter.
N: Superior gluteal nerves.
A: Abducts & medially rotates thigh.
Tensor Fascia Lata
O: Anterior superior iliac spine.
I: Iliotibial tract.
N: Superior gluteal nerves.
A: tenses fascia lata, flexes, abducts, & medially rotates thigh. Extends knee w/ lateral rotation of leg.
Gemellus Superior
O: Ischial spine.
I: Trochanteric fossa.
N: Nerve to obturator internus muscle.
A: Rotates extended thigh laterally. Abducts flexed thigh.
Gemellus Inferior
O: Ischial tuberosity.
I: Trochanteric fossa.
N: Nerve to quadratus femoris muscle.
A: Rotates extended thigh laterally & abducts flexed thigh.
Obturator Internus

[model only]
O: Pelvic surface of obturator membrane & surrounding bone.
I: Trochanteric fossa.
N: Nerve to obturator internus muscle.
A: Rotates extended thigh laterally & abducts flexed thigh.
Obturator Externus

[MALE model only]
O: External surface of the obturator membrane & bone around obturator foramen.
I: Trochanteric fossa.
N: Obturator nerve.
A: Lateral rotator of thigh.
Piriformis

[model only]
O: Anterior / pelvic surface of sacrum.
I: Greater trochanter of femur.
N: Piriformis branch of sacral plexus.
A: Rotates thigh laterally & abducts flexed thigh.
Quadratus Femoris
O: Ischial tuberosity.
I: Intertrochanteric crest.
N: Nerve to quadratus femoris muscle.
A: lateral rotator of thigh.
Sartorius
O: Anterior superior iliac spine.
I: Medial surface of upper tibia.
N: Femoral nerve.
A: flexes leg on thigh and thigh on pelvis. Adbucts & laterally rotates thigh. Rotates leg medially.
Quadriceps Femoris

(composed of four muscles)
1- Rectus femoris
2- Vastus lateralis
3- Vastus medialis
4- Vastus intermedius
Rectus Femoris

- part of Quadriceps Femoris
O: Anterior inferior iliac spine.
I: Tibial tuberosity via patellar tendon.
N: Femoral nerve.
A: Flexes hip & extends knee.
Vastus Lateralis

- part of Quadriceps Femoris
O: Greater trochanter & upper half of lateral lip of linea aspera.
I: Tibial tuberosity via patellar tendon.
N: Femoral nerve.
A: Extension of knee.
Vastus Medialis

- part of Quadriceps Femoris
O: Lower part of intertrochanteric line and medial lip of lines aspera.
I: Tibial tuberosity via patellar tendon.
N: Femoral nerve.
A: Extension of knee.
Vastus Intermedius

- part of Quadriceps Femoris
O: Front & lateral surface of upper 2/3's of femoral shaft.
I: Tibial tuberosity via patellar tendon.
N: Femoral nerve.
A: Extension of knee.
Gracilis
O: Body & inferior ramus of pubis.
I: Shaft of tibia below the medial condyle.
N: Obturator nerve.
A: Adducts thigh, flexes knee, assists in rotating flexed leg medially.
Pectineus
O: Pectineal line of pubis & region of pubis anterior to this line.
I: Pectineal line of femur.
N: Femoral nerve & obturator nerve.
A: Adducts & flexes thigh. Laterally rotates thigh.
Adductor Longus
O: Crest & symphysis of pubis.
I: Middle 1/3 of medial lip of linea aspera of femur.
N: Obturator nerve.
A: Adduction of thigh, assists in flexion & lateral rotation of thigh.
Adductor Brevis
O: Inferior ramus of pubis.
I: Upper 1/3 of medial lip of the linea aspera.
N: Obturator nerve.
A: Adduction of thigh. Assists in flexion & lateral rotation of thigh.
Adductor Magnus

(Adductor Portion)
O: Body of pubis, inferior pubic ramus, ischial ramus.
I: Entire length of linea aspera.
N: Obturator nerve.
A: Adductor & extensor of thigh. Also flexor and lateral rotator.
Adductor Magnus

(Extensor Portion)
O: Ischial ramus, ischial tuberosity.
I: Adductor tubercle.
N: Tibial nerve.
A: Adductor & extensor of thigh. Also extensor and medial rotator.
Semimembranosus
O: Ischial tuberosity.
I: Medial condyle of tibia.
N: Tibial nerve.
A: Flexes leg, rotates leg medially, & extends hip.
Semitendinosus
O: Ischial tuberosity.
I: Medial surface of proximal tibia.
N: Tibial nerve.
A: Flexes leg, rotates leg medially, & extends hip.
Biceps Femoris

[Long Head]
O: Ischial tuberosity.
I: Head of fibula and lateral condyle of tibia.
N: Tibial nerve.
A: Flexes knee, rotates leg medially, extension of hip.
Biceps Femoris

[Short Head]
O: Lower 1/2 of lateral lip of linea aspera.
I: Head of fibula & lateral condyle of tibia.
N: Common peroneal nerve.
A: Flexes knee, rotates leg laterally.
Superior Extensor Retinaculum
Band, indistinguishable from muscle fascia, running between tibia and fibula on anterior surface of leg, above ankle.
Tibialis Anterior
(TOM)
O: Upper 2/3's lateral surface & lateral condyle tibia.
I: Medial cuneiform bone & base of 1st metatarsal bone.
N: Deep peroneal nerve.
A: Dorsiflexion of foot & inverts the foot.
Extensor Digitorum Longus
(DICK)
O: Lateral condyle of the upper 3/4's of fibula.
I: Four lateral toes. Extensor aponeurosis over middle phalanx of the toe.
N: Deep peroneal nerve.
A: Extends 2-5 toes, dorsiflexes and everts foot.
Extensor Hallucis Longus
(HARRY)
O: Middle half of fibula.
I: Base of distal phalanx of great toe.
N: Deep peroneal nerve.
A: Extends great toe, dorsiflexes foot, inverts foot.
Peroneus Tertius
O: Lower 1/3 of fibula.
I: Base of 5th metatrasal bone.
N: Deep peroneal nerve.
A: Dorsiflexes and everts the foot.
Peroneus Longus
O: Head & upper 2/3's of the fibula.
I: Base of 1st metatarsal bone & medial cuneiform bone.
N: Superficial peroneal nerve.
A: Abducts & everts foot. Aids in plantar flexion.
Peroneus Brevis
O: Lower 2/3's of fibula.
I: Tuberosity on the base of the 5th metatarsal bone.
N: Superficial peroneal nerve.
A: Prevents over-inversion of foot, abducts & everts foot, & aids in plantar flexion.
Gastrocnemius
O: [Medial Head] Popliteal surface and medial condyle of femur.
[Lateral Head] Lateral condyle of femur.
I: Tendocalcaneus (Achilles' Tendon) into lower 1/2 of posterior surface of calcaneus.
N: Tibial nerve.
A: Plantar flexor of foot. Flexor of knee.
Soleus
O: Upper 1/4 of the fibula and soleal line of tibia.
I: Achilles' tendon into lower 1/2 of posterior surface of calcaneus.
N: Tibial nerve.
A: Plantar flexor of foot.
Plantaris
O: Lateral supracondylar ridge of femur.
I: Achilles' tendon.
N: Tibial nerve.
A: Plantar flexion of leg & foot.
Tibialis Posterior
(TOM)
O: Posterior surfaces of shafts of fibula and tibia.
I: Tuberosity of the navicular, bases of 2-4 metatarsal bones; attachments to all tarsal bones except talus & calcaneus.
N: Tibial nerve.
A: Primary supinator of foot. Assists with plantar flexion.
Flexor Digitorum Longus
(DICK)
O: Middle 1/3 of the posterior shaft of the tibia below soleal line.
I: Bases of distal phalanges of toes 2-5.
N: Tibial nerve.
A: Plantar flexion, supination, & flexes four lateral toes.
Flexor Hallucis Longus
(HARRY)
O: Inferior 2/3's of the posterior surface of fibula.
I: Base of distal phalanx of the great toe.
N: Tibial nerve.
A: Flexes great toe, plantar flexion and supination of foot.
Popliteus
O: Anterior end of the popliteal groove on lateral condyle of femur.
I: Area above soleal line on posterior surface of tibia.
N: Tibial nerve.
A: Flexes leg and rotates tibia medially; rotates femur laterally.
Extensor Digitorum Brevis /
Extensor Hallucis Brevis
O: Calcaneus.
I: [Extensor Hallucis Brevis]- Base of proximal phalanx of the great toe.
[Extensor Digitorum Brevis]- Tendons of extensor digirorum longus to 2-4 toes.
N: Deep peroneal nerve.
A: Extension of phalanges of 2-4 toes. Extends great toe at metatarsophalangeal joint.
Abductor Hallucis

{Layer #1}
O: Medial process of tuberosity of calcaneus.
I: Medial side of proximal phalanx of great toe.
N: Medial plantar nerve.
A: Abduction of great toe.
Abductor Digiti Minimi

(Layer #1)
O: Medial and Lateral processes of tuberosity of calcaneus.
I: Base of proximal phalanx of the 5th toe.
N: Lateral plantar nerve.
A: Abduction of small toe.
Flexor Digitorum Brevis

(Layer #1)
O: Medial process of calcaneal tuberosity.
I: Middle phalanx of toes 2-5.
N: Medial plantar nerve.
A: Aids in flexing distal phalanges 2-5 toes.
Quadratus Plantae

(Layer #2)
O: Calcaneus.
I: Tendon of flexor digitorum longus.
N: Lateral plantar nerve.
A: Flexing distal phalanges of toes 2-5.
Lumbricals {x4}

(Layer #2)
O: From at tibial side [#1] or adjacent sides [#2-4] of flexor digitorum longus tendons to toes 2-5.
I: Tibial side of proximal phalanx of toes 2-5 & tibial side of aponeurotic expansion over distal 2 phalanges of toes 2-5.
N: [1]- Medial plantar nerve. [2-4]- Lateral plantar nerve.
A: Flexes metatarsophalangeal joints of toes 2-5.
Flexor Hallucis Brevis

(Layer #3)
O: Cuboid, middle & lateral cuneiform bones.
I: Medial side of base of proximal phalanx of great toe.
N: Medial plantar nerve.
A: Flexes proximal phalanx of great toe.
Adductor Hallucis
[Oblique Head]

(Layer #3)
O: Lateral cuneiform bone & bases of 3rd & 4th metatarsal bones.
I: Base of proximal phalanx of great toe.
N: Lateral plantar nerve.
A: Adducts great toe.
Adductor Hallucis
[Transverse Head]

(Layer #3)
O: Capsules of lateral four metatarsophalangeal joints.
I: Base of proximal phalanx of the great toe.
N: Lateral plantar nerve.
A: Adducts great toe.
Flexor Digiti Minimi Brevis

(Layer #3)
O: Base of 5th metatarsal bone.
I: Base of proximal phalanx of 5th toe.
N: Lateral plantar nerver.
A: Flexes proximal phalanx of small toe.
Dorsal Interossei {x4}

(Layer #4)
O: Bipennate, taking origin from adjacent sides of bases & shafts of two metatarsal bones.
I: [1]- Tibial side of base of proximal phalanx of toe 2. [2-4]- Fibular side of base of proximal phalanx of toes 2-4.
N: Lateral plantar nerve.
A: Abducts toes 2-4.
Plantar Interossei {x3}

(Layer #4)
O: Medial side of the base & body of metatarsals 3-5.
I: Medial side of base of proximal phalanx of toes 3-5.
N: Lateral plantar nerve.
A: Adducts toes 3-5.
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