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Human Muscles

Comprehensive guides to 23 major muscles covering origin, insertion, action, innervation, and clinical relevance. Perfect for medical students, physical therapists, and fitness professionals.

Upper Limb

Biceps Brachii

Flexion of the elbow joint

Musculocutaneous nerve

Triceps Brachii

Extension of the elbow joint (all three heads)

Radial nerve

Deltoid

Abduction of the arm (middle fibers - main abductor after first 15°)

Axillary nerve

Rotator Cuff

Supraspinatus: Initiates abduction (first 15°), stabilizes shoulder

Supraspinatus: Suprascapular nerve

Rhomboids

Retraction of the scapula (pulling shoulder blades together)

Dorsal scapular nerve

Trunk & Core

Pectoralis Major

Adduction of the arm

Medial pectoral nerve

Latissimus Dorsi

Extension of the arm

Thoracodorsal nerve

Rectus Abdominis

Flexion of the trunk (against gravity)

Intercostal nerves

Trapezius

Elevation of the scapula (upper fibers)

Accessory nerve

Diaphragm

Primary muscle of inspiration (contraction flattens the dome)

Phrenic nerve

External Obliques

Flexion of the trunk (bilateral contraction)

Intercostal nerves

Erector Spinae

Extension of the vertebral column (bilateral contraction)

Posterior rami of spinal nerves

Lower Limb

Gluteus Maximus

Extension of the hip (most powerful hip extensor)

Inferior gluteal nerve

Quadriceps Femoris

Extension of the knee (all four muscles)

Femoral nerve

Hamstrings

Flexion of the knee (all three muscles)

Sciatic nerve - tibial division

Gastrocnemius

Plantarflexion of the ankle (strongest plantarflexor)

Tibial nerve

Iliopsoas

Flexion of the hip (strongest hip flexor)

Psoas major: Lumbar plexus

Soleus

Plantarflexion of the ankle

Tibial nerve

Tibialis Anterior

Dorsiflexion of the ankle

Deep fibular

Sartorius

Flexion of the hip