Muscle Anatomy and Naming Conventions: Key Terms and Definitions

Rectus (straight)

Muscle fibers run parallel to the midline (e.g., rectus abdominis)

Oblique (angled)

Muscle fibers run at an angle to the midline (e.g., external oblique)

Orbicularis (circular)

Circular muscle fibers around openings (e.g., orbicularis oculi)

Deltoid (triangular)

Triangular-shaped muscle

Quadratus (rectangular)

Rectangular-shaped muscle

Trapezius (trapezoidal)

Trapezoid-shaped muscle

Longus (long)

Long muscle

Brevis (short)

Short muscle

Major

Larger of two muscles (e.g., pectoralis major)

Minor

Smaller of two muscles (e.g., pectoralis minor)

Maximus

Largest muscle of a group (e.g., gluteus maximus)

Medius

Medium-sized muscle (e.g., gluteus medius)

Minimus

Smallest muscle of a group (e.g., gluteus minimus)

Biceps

Muscle with two heads (e.g., biceps femoris)

Triceps

Muscle with three heads (e.g., triceps brachii)

Quadriceps

Muscle with four heads (e.g., quadriceps femoris)

Adductor

Moves body part toward midline (e.g., adductor magnus)

Abductor

Moves body part away from midline (e.g., abductor pollicis longus)

Flexor

Bends or decreases joint angle (e.g., flexor carpi radialis)

Extensor

Straightens or increases joint angle (e.g., extensor hallucis longus)

Oris

Refers to mouth (e.g., orbicularis oris)

Cervicis

Refers to neck (e.g., semispinalis cervicis)

Brachial

Refers to arm (e.g., biceps brachii)

Carpi

Refers to wrist (e.g., flexor carpi ulnaris)

Pollicis

Refers to thumb (e.g., opponens pollicis)

Gluteal

Refers to buttocks (e.g., gluteus medius)

Femoris

Refers to thigh (e.g., quadratus femoris)

Hallucis

Refers to great toe (e.g., extensor hallucis longus)

Anterior

Toward the front of the body (e.g., tibialis anterior)

Posterior / Dorsal

Toward the back of the body (e.g., latissimus dorsi)

Superior

Closer to the head (e.g., serratus posterior superior)

Inferior

Closer to the feet (e.g., serratus posterior inferior)

Superficialis

Toward the surface (e.g., flexor digitorum superficialis)

Profundus

Deep muscle (e.g., flexor digitorum profundus)

Cleido / Sternocleido

Attached to sternum and clavicle (e.g., sternocleidomastoid)

Intercostal

Between the ribs (e.g., intercostals)

Subscapularis

Beneath the scapula (e.g., subscapularis)

Fibularis / Peroneus

Attached to fibula (e.g., fibularis longus)

Zygomaticus

Attached to zygomatic bone (e.g., zygomaticus major)