Muscle Anatomy: Origins, Insertions, Innervations, and Actions

These flashcards cover the origins, insertions, innervations, and actions of various muscles, focusing on the gluteal region, thigh, hip flexors, and legs.

Gluteus maximus

Origin: Ilium posterior to posterior gluteal line, dorsal sacrum, coccyx, sacrotuberous ligament; Insertion: Iliotibial tract, lateral condyle of tibia, gluteal tuberosity of femur; Innervation: Inferior gluteal nerve; Action: Extends flexed thigh, assists in lateral rotation, and abducts thigh.

Gluteus medius

Origin: Lateral surface of ilium between anterior and posterior gluteal lines; Insertion: Greater trochanter of femur; Innervation: Superior gluteal nerve; Action: Abducts and medially rotates thigh at hips; steadies pelvis on leg when opposite leg is raised.

Gluteus minimus

Origin: Lateral surface of ilium between anterior and inferior gluteal lines; Insertion: Greater trochanter of femur; Innervation: Superior gluteal nerve; Action: Abducts and medially rotates thigh.

Piriformis

Origin: Anterior surface of sacral segments 2–4, sacrotuberous ligament; Insertion: Greater trochanter of femur; Innervation: Nerve to piriformis (Posterior rami of S1-S2); Action: Laterally rotates extended thigh, abducts flexed thigh.

Quadratus femoris

Origin: Ischial tuberosity; Insertion: Intertrochanteric crest of femur; Innervation: Nerve to quadratus femoris muscle (L4–S1); Action: Laterally rotates thigh at hip.

Biceps femoris

Origin: Long head - ischial tuberosity, Short head - linea aspera; Insertion: Lateral head of fibula; Innervation: Long head - sciatic nerve (tibial division), Short head - sciatic nerve (common fibular division); Action: Flexes and laterally rotates leg, extends thigh at hip.

Semimembranosus

Origin: Upper and lateral ischial tuberosity; Insertion: Posterior medial condyle of tibia; Innervation: Tibial division of sciatic nerve; Action: Flexes leg, extends thigh.

Adductor magnus

Origin: Adductor part - inferior pubic ramus, ramus of ischium; Insertion: Adductor part - gluteal tuberosity, linea aspera, supracondylar line; Innervation: Adductor part - obturator nerve; Hamstring part - tibial nerve; Action: Adductor part - adducts and flexes thigh, Hamstring part - extends thigh.

Psoas major

Origin: Transverse processes of lumbar vertebrae, T12–L5; Insertion: Lesser trochanter of femur; Innervation: Anterior rami of first four lumbar nerves; Action: Acting superiorly with iliacus, flexes hip; acting inferiorly, flexes vertebral column laterally.

Tibialis anterior

Origin: Lateral condyle and proximal half of lateral tibia; Insertion: Medial plantar surfaces of medial cuneiform bone and base of 1st metatarsal bone; Innervation: Deep fibular nerve; Action: Dorsiflexes foot at ankle and inverts foot.

Flexor digitorum longus

Origin: Medial part of posterior tibia inferior to soleal line; Insertion: Plantar bases of distal phalangeal bones of lateral four digits; Innervation: Tibial nerve; Action: Flexes lateral four digits and plantarflexes foot at ankle.

Extensor digitorum longus

Origin: Lateral condyle of tibia, proximal three-fourths of anterior surface of interosseous membrane and fibula; Insertion: Middle and distal phalangeal bones of lateral four digits; Innervation: Deep fibular nerve; Action: Extends lateral four digits and dorsiflexes foot at ankle.

Gastrocnemius

Origin: Lateral head - lateral aspect of lateral condyle of femur; Medial head - popliteal surface above medial condyle of femur; Insertion: Posterior aspect of calcaneus via the calcaneal tendon; Innervation: Tibial nerve; Action: Plantarflexes foot at ankle joint, assists in flexion of knee joint.