Muscular Anatomy: Origin, Insertion, and Action

Vocabulary practice flashcards covering origins, insertions, and actions of muscles of the head, neck, thorax, shoulder, abdomen, upper limb, pelvis, thigh, and leg.

Frontalis

Origin: Epicranial aponeurosis | Insertion: Skin/subcutaneous tissue of eyebrows/forehead | Action: Eyebrow raising

Orbicularis oculi

Origin: Medial orbital | Insertion: Lateral palpebral raphe, tarsal plates (eyelids), orbital margin skin | Action: Eyelid closing

Orbicularis oris

Origin: Modiolus, buccinator, maxilla/mandible, lacrimal bone | Insertion: Modiolus, skin/mucous membrane of lips | Action: Lip closing/pursing

Buccinator

Position: Deep to zygomaticus minor/major | Origin: Alveolar processes of maxilla/mandible | Insertion: Modiolus | Action: Cheek compression

Zygomaticus major (inferior)

Origin: Zygomatic bone | Insertion: Modiolus (angle of mouth) | Action: Smiling

Zygomaticus minor (superior)

Origin: Zygomatic bone | Insertion: Upper lip | Action: Upper lip elevation

Masseter

Origin: Zygomatic arch | Insertion: Angle, ramus & coronoid process of mandible | Action: Mandibular elevation/protraction

Temporalis

Origin: Temporal fossa | Insertion: Ramus & coronoid process of mandible | Action: Mandibular elevation/retraction

Sternocleidomastoid (SCM)

Origin: Medial clavicle, manubrium | Insertion: Mastoid process, superior nuchal line | Action: Neck flexion, contralateral head rotation

Sternohyoid

Origin: Medial clavicle, manubrium | Insertion: Hyoid | Action: Hyoid depression

Digastric

Origin: Digastric fossa of mandible, mastoid notch | Insertion: Hyoid | Action: Hyoid elevation, mandibular depression

Thyrohyoid

Origin: Thyroid cartilage | Insertion: Hyoid | Action: Hyoid depression

Serratus anterior

Origin: Lateral surfaces of ribs 1–8/9 | Insertion: Anterior medial surface of scapula | Action: Scapular protraction/upward rotation

Pectoralis minor (deep)

Origin: Ribs 3–5 | Insertion: Coracoid process of scapula | Action: Scapular protraction/depression

Pectoralis major

Origin: Clavicle, sternum, & costal cartilages of ribs 1-6 | Insertion: Lateral lip of intertubercular groove of humerus | Action: Arm medial rotation, shoulder adduction/forward flexion, extension (downward)

Teres major

Origin: Posterior inferior angle/lateral border of scapula | Insertion: Medial lip of intertubercular groove of humerus | Action: Shoulder adduction, medial rotation, extension & stabilization

Subscapularis

Origin: Subscapular fossa | Insertion: Lesser tubercle of humerus | Action: Shoulder adduction, medial rotation & stabilization

Supraspinatus (deep)

Origin: Supraspinous fossa | Insertion: Greater tubercle of humerus | Action: Shoulder abduction ($0-15^\top$) -> assists deltoid ($16-90^\top$), shoulder stabilization

Deltoid

Origin: Lateral clavicle, acromion, scapular spine (clavicular/acromial/spinal parts) | Insertion: Deltoid tuberosity of humerus | Action: Shoulder abduction, flexion/extension, & medial/lateral rotation

Abdominal Muscles (Shared Actions)

Shared functional actions of the abdominal wall musculature: stabilizes pelvis, compresses abdomen, forced expiration/expulsion

Rectus abdominis

Origin: Pubic crest/symphysis | Insertion: Xiphoid process, linea alba, ribs 5–7 costal cartilages | Action: Spinal flexion

External oblique

Origin: External surfaces of ribs 5–12 | Insertion: Anterior iliac crest, linea alba, pubic crest & symphysis | Action: Spinal contralateral rotation, lateral flexion & flexion

Internal oblique

Origin: Thoracolumbar fascia, iliac crest, inguinal ligament | Insertion: Ribs 10-12, linea alba, pubic crest, pectineal line | Action: Spinal ipsilateral rotation, lateral flexion & flexion

Transversus abdominis

Origin: Thoracolumbar fascia, iliac crest, inguinal ligament, costal cartilages of ribs 7-12 | Insertion: Xiphoid process, linea alba, pubic crest, pectineal line | Action: Intra-abdominal pressure

Biceps brachii

Origin: Supraglenoid tubercle (long head) / coracoid process (short head) | Insertion: Radial tuberosity and forearm fascia | Action: Forearm supination, elbow/shoulder flexion

Coracobrachialis (deep)

Origin: Coracoid process of scapula | Insertion: Middle medial humerus | Action: Shoulder flexion/adduction & stabilization

Brachialis

Origin: Anterior distal humerus | Insertion: Ulnar tuberosity/coronoid process | Action: Elbow flexion

Brachioradialis

Origin: Lateral supracondylar ridge of humerus | Insertion: Distal radius | Action: Elbow flexion (esp. neutral forearm)

Flexor carpi radialis

Origin: Medial epicondyle of humerus | Insertion: Bases of metacarpals II-III | Action: Wrist flexion/abduction

Palmaris longus

Feature: Absent in $10-20\%$ of people | Origin: Medial epicondyle of humerus | Insertion: Palmar aponeurosis and flexor retinaculum | Action: Wrist flexion, tenses palmar aponeurosis (grip)

Flexor carpi ulnaris

Origin: Medial epicondyle of humerus & ulnar olecranon | Insertion: Base of metacarpal V, pisiform, hamate | Action: Wrist flexion/adduction

Flexor digitorum superficialis

Origin: Medial epicondyle of humerus, ulnar coronoid process | Insertion: Sides of middle phalanges II-V | Action: Middle phalanges, MCP, & wrist flexion

Pronator teres

Origin: Medial epicondyle & supracondylar ridge of humerus | Insertion: Middle lateral radius | Action: Forearm pronation, elbow flexion

Flexor pollicis brevis

Origin: Flexor retinaculum | Insertion: Lateral base of proximal phalanx I | Action: Thumb flexion (at MCP/CMC)

Abductor pollicis brevis

Origin: Flexor retinaculum | Insertion: Lateral base of proximal phalanx I | Action: Thumb abduction

Sartorius

Feature: Longest muscle | Origin: ASIS | Insertion: Medial proximal tibia | Action: Hip flexion, abduction and lateral rotation; knee flexion (cross-legged sitting)

Gracilis

Origin: Body and inferior ramus of pubis | Insertion: Medial proximal tibia | Action: Hip adduction/flexion, knee flexion

Adductor longus

Origin: Body of pubis | Insertion: Middle linea aspera | Action: Hip adduction/flexion

Adductor brevis (deep)

Origin: Body and inferior ramus of pubis | Insertion: Proximal linea aspera | Action: Hip adduction

Rectus femoris

Origin: AIIS | Insertion: Patella base, tibial tuberosity | Action: Hip flexion, knee extension

Vastus lateralis

Feature: Largest quad muscle | Origin: Lateral lip of linea aspera, intertrochanteric line, greater trochanter & gluteal tuberosity of femur | Insertion: Patella base, tibial tuberosity | Action: Knee extension

Vastus intermedius

Position: Deep to rec. fem. | Origin: Proximal lateral femoral shaft | Insertion: Patella base, tibial tuberosity | Action: Knee extension

Vastus medialis

Origin: Medial lip of linea aspera, intertrochanteric line, medial supracondylar ridge of femur | Insertion: Patella base, tibial tuberosity | Action: Knee extension, patellar stabilization

Iliotibial tract

Origin: Iliac crest | Insertion: Lateral condyle of tibia | Action: Hip abduction, extension, lateral rotation; Knee flexion/extension (first $0-30^\circ$)

Tensor fasciae latae

Origin: ASIS, iliac crest | Insertion: Iliotibial tract -> lateral condyle of tibia | Action: Hip abduction, flexion, medial rotation

Illiacus

Origin: Iliac crest | Insertion: Lesser trochanter of femur | Action: Hip flexion

Psoas major

Origin: Lumbar vertebrae | Insertion: Lesser trochanter of femur | Action: Hip flexion

Fibularis (peroneus) longus

Origin: Head of/proximal fibula | Insertion: Medial cuneiform, metatarsal I base | Action: Eversion, plantarflexion, supports arches

Fibularis (peroneus) brevis

Origin: Distal fibula | Insertion: Metatarsal V base | Action: Eversion, plantarflexion

Tibialis anterior

Origin: Lateral condyle & proximal surface of tibia | Insertion: Medial cuneiform, metatarsal I base | Action: Inversion, dorsiflexion

Extensor digitorum longus

Origin: Lateral condyle of tibia, proximal fibula | Insertion: Middle/distal phalanges of digits II-V | Action: Toe extension, dorsiflexion

Extensor hallucis longus

Origin: Anterior fibula/interosseous membrane | Insertion: Distal phalanx of digit I | Action: Hallux extension, dorsiflexion