Muscle Origins, Insertions, and Actions Reference Table

Orbicularis oculi

Medial margin of orbit; frontal & maxillary bones. Closes eyelids; squinting/blinking.

Orbicularis oris

Maxilla & mandible, modiolus. Compresses & purses lips ("kissing").

Temporalis

Temporal bone. Elevates & retracts mandible.

Sternocleidomastoid

Manubrium of sternum; medial clavicle. Bilateral - neck flexion; Unilateral - rotates head to opposite side.

Rectus abdominis

Pubic symphysis & crest. Flexes vertebral column; compresses abdomen.

External oblique

Lower 5-12 ribs (external surfaces). Compresses abdomen; trunk flexion & contralateral rotation.

Internal oblique

Thoracolumbar fascia; iliac crest. Compresses abdomen; trunk flexion & ipsilateral rotation.

Trapezius

Occipital bone; ligamentum nuchae; C7-T12 spinous processes. Scapular elevation, retraction, depression; extends neck.

Pectoralis major

Medial clavicle; sternum; costal cartilages 1‑6. Flexes, adducts, & medially rotates humerus.

Latissimus dorsi

Thoracolumbar fascia; T7-L5 spinous processes; iliac crest. Extends, adducts, & medially rotates humerus.

Deltoid

Spine & acromion of scapula; lateral clavicle. Abducts arm (whole); anterior fibers - flex/medially rotate; posterior - extend/laterally rotate.

Supraspinatus

Supraspinous fossa (scapula). Initiates & assists abduction.

Infraspinatus

Infraspinous fossa (scapula). Lateral rotation of arm.

Biceps brachii

Short head - coracoid process; long head - supraglenoid tubercle. Flexes elbow & supinates forearm; weak shoulder flexion.

Brachioradialis

Lateral supracondylar ridge (humerus). Flexes elbow (best in mid‑pronation).

Triceps brachii

Long head - infraglenoid tubercle; lateral & medial heads - posterior humerus. Extends elbow; long head assists shoulder extension.

Palmaris longus

Medial epicondyle (humerus). Weak wrist flexion; tenses palmar fascia.

Extensor digitorum

Lateral epicondyle (humerus). Extends fingers and wrist.

Iliopsoas (psoas + iliacus)

Psoas - T12-L5 bodies & TPs; Iliacus - iliac fossa. Powerful hip flexion; trunk flexion when femur fixed.

Sartorius

ASIS. Flexes, abducts, laterally rotates hip; flexes knee.

Rectus femoris

AIIS; superior acetabular rim. Extends knee; flexes hip.

Vastus lateralis

Greater trochanter; lateral linea aspera. Extends knee.

Vastus medialis

Intertrochanteric line; medial linea aspera. Extends knee.

Tensor fasciae latae

Anterior iliac crest & ASIS. Abducts & medially rotates hip; steadies IT band.

Gluteus maximus

Posterior ilium; sacrum; coccyx; sacrotuberous lig.

Gluteal tuberosity & IT band

Extends & laterally rotates hip

Biceps femoris

Long head - ischial tuberosity; short head - linea aspera; Head of fibula; Flexes knee; long head extends & laterally rotates hip

Semimembranosus

Ischial tuberosity; Posterior medial tibial condyle; Flexes knee; extends & medially rotates hip

Semitendinosus

Ischial tuberosity; Medial proximal tibia (pes anserinus); Flexes knee; extends & medially rotates hip

Tibialis anterior

Lateral condyle & upper 2/3 tibia; interosseous membrane; Medial cuneiform & base 1st metatarsal; Dorsiflexes & inverts foot

Gastrocnemius

Posterior medial & lateral femoral condyles; Calcaneus via Achilles tendon; Plantar‑flexes ankle; assists knee flexion

Flexor digitorum longus

Posterior tibia; Distal phalanges toes 2‑5 (plantar); Flexes toes 2‑5; plantar‑flexes & inverts foot

Extensor digitorum longus

Lateral tibial condyle; proximal fibula; interosseous membrane; Dorsal digital expansions toes 2‑5; Extends toes 2‑5; dorsiflexes ankle