Learn / Muscles
Every muscle
All 69 muscles from the ANI summary slides — back and suboccipital (1.1), shoulder (2.3), pectoral (2.4), arm (4.1), forearm (4.2), hand (4.3) and thoracic wall (6.1). Learn them by nerve and compartment, then let the drill hammer the exceptions; the Lesion mode turns a nerve injury into what the patient can't do. Every answer names the nerve (with roots where the lecture gave them).
Group by
Back — extrinsic, superficial layer 5
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Trapezius ANI 1.1 Back & Suboccipital Upper + lower fibres together upwardly rotate the scapula for abduction past 90°. Borders the triangle of auscultation. |
External occipital protuberance, superior nuchal line, ligamentum nuchae, spines of C7–T12 | Spine of scapula, acromion & lateral third of clavicle | Spinal accessory n. (CN XI) | Transverse cervical a. (superficial branch) | Elevate scapula (upper fibres); Retract/adduct scapula (middle fibres); Depress scapula (lower fibres); Upwardly rotate scapula (upper + lower together) |
| Latissimus dorsi ANI 1.1 Back & Suboccipital 'Widest of the back'. Raises the trunk to the arm (climbing). The anterior insertion is why it medially rotates. Borders the triangle of auscultation. |
Spines of T7–T12, thoracolumbar fascia, iliac crest, ribs 9–12 | Intertubercular groove of humerus | Thoracodorsal n. (C6, C7, C8) | Thoracodorsal a. (via subscapular a.) | Adduct arm; Extend arm; Medially rotate arm; Depress scapula |
| Levator scapulae ANI 1.1 Back & Suboccipital |
Transverse processes of C1–C4 | Medial border of scapula at the superior angle | Dorsal scapular n. (C4, C5) | Dorsal scapular a. (deep branch of transverse cervical a.) | Elevate scapula; Downwardly rotate scapula |
| Rhomboid minor ANI 1.1 Back & Suboccipital Dorsal scapular nerve damage → ipsilateral scapula sits farther from the midline. |
Spines of C7–T1 | Root of the spine of the scapula (medial border) | Dorsal scapular n. (C4, C5) | Dorsal scapular a. (deep branch of transverse cervical a.) | Retract/adduct scapula |
| Rhomboid major ANI 1.1 Back & Suboccipital |
Spines of T2–T5/T6 | Medial border of scapula below the spine | Dorsal scapular n. (C4, C5) | Dorsal scapular a. (deep branch of transverse cervical a.) | Retract/adduct scapula |
Back — extrinsic, intermediate layer 2
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Serratus posterior superior ANI 1.1 Back & Suboccipital Serra = saw. Mostly proprioceptive. |
Supraspinous ligament & spines of C7–T3 | Ribs 2–5 | Intercostal nn. | Intercostal aa. | Elevate ribs (assist inspiration); Proprioception |
| Serratus posterior inferior ANI 1.1 Back & Suboccipital |
Supraspinous ligament & spines of T11–L2 | Ribs 9–12 | Intercostal nn. | Intercostal aa. | Depress ribs (assist expiration); Proprioception |
Back — intrinsic (deep) 7
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Splenius capitis ANI 1.1 Back & Suboccipital Spinotransversalis (superficial intrinsic) layer — 'bandage' muscles. Blood supply varies: deep cervical, posterior intercostal, subcostal or lumbar aa. |
Ligamentum nuchae & spines of C7–T6 | Mastoid process & lateral superior nuchal line | Posterior rami of spinal nn. | Extend head & neck (bilateral); Rotate head & neck to same side (unilateral) | |
| Splenius cervicis ANI 1.1 Back & Suboccipital Same plane as splenius capitis. |
Spines of T3–T6 | Transverse processes of C1–C3/C4 | Posterior rami of spinal nn. | Extend head & neck (bilateral); Rotate head & neck to same side (unilateral) | |
| Iliocostalis ANI 1.1 Back & Suboccipital Erector spinae, lateral column — 'I Love Spinach' lateral → medial. |
Broad tendon from iliac crest, sacrum & spinous processes (thoracolumbar fascia) | Ribs & cervical transverse processes (lumborum, thoracis, cervicis) | Posterior rami of spinal nn. | Extend vertebral column & head (bilateral); Laterally flex vertebral column to same side (unilateral) | |
| Longissimus ANI 1.1 Back & Suboccipital Erector spinae, intermediate column; the only erector spinae part that reaches the skull (capitis). |
Broad tendon from iliac crest & sacrum | Ribs, cervical/thoracic transverse processes & mastoid process (thoracis, cervicis, capitis) | Posterior rami of spinal nn. | Extend vertebral column & head (bilateral); Laterally flex vertebral column to same side (unilateral) | |
| Spinalis ANI 1.1 Back & Suboccipital Erector spinae, medial column. Spinalis cervicis attaches to the C2 spinous process. |
Spinous processes (thoracolumbar) | Spinous processes above (thoracis, cervicis to C2) | Posterior rami of spinal nn. | Extend vertebral column & head (bilateral); Laterally flex vertebral column to same side (unilateral) | |
| Semispinalis ANI 1.1 Back & Suboccipital Transversospinalis layer; capitis overlies cervicis (different planes). Semispinalis cervicis attaches to C2. |
Transverse processes of C4–T12 | Spinous processes 4–6 segments above; capitis to the occipital bone | Posterior rami of spinal nn. | Extend spine & head (bilateral); Rotate head & spine to opposite side (unilateral); Maintain posture | |
| Multifidus ANI 1.1 Back & Suboccipital Transversospinalis layer; deepest of the three C2 attachments; largest in the lumbar region. |
Sacrum & transverse processes | Spinous processes 2–4 segments above, up to C2 | Posterior rami of spinal nn. | Stabilise vertebrae during local movements; Maintain posture |
Suboccipital 4
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Rectus capitis posterior major ANI 1.1 Back & Suboccipital Medial border of the suboccipital triangle. Supplied by vertebral & occipital aa. |
Spinous process of C2 | Lateral inferior nuchal line | Suboccipital n. (posterior ramus of C1) | Vertebral & occipital aa. | Extend head (bilateral); Rotate head to same side (unilateral) |
| Rectus capitis posterior minor ANI 1.1 Back & Suboccipital The only suboccipital muscle that is not part of the suboccipital triangle. |
Posterior tubercle of C1 | Medial inferior nuchal line | Suboccipital n. (posterior ramus of C1) | Vertebral & occipital aa. | Extend head (bilateral) |
| Obliquus capitis superior ANI 1.1 Back & Suboccipital Superolateral border of the suboccipital triangle. |
Transverse process of C1 | Occipital bone between the nuchal lines | Suboccipital n. (posterior ramus of C1) | Vertebral & occipital aa. | Extend head (bilateral) |
| Obliquus capitis inferior ANI 1.1 Back & Suboccipital Inferolateral border of the suboccipital triangle; the only 'capitis' that doesn't reach the skull. |
Spinous process of C2 | Transverse process of C1 | Suboccipital n. (posterior ramus of C1) | Vertebral & occipital aa. | Extend head (bilateral); Rotate head to same side (unilateral) |
Shoulder — scapulohumeral 6
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Deltoid ANI 2.3 Scapular Region Axillary nerve lesion (surgical neck fracture, dislocation) → deltoid atrophy, flattened shoulder, numb 'regimental badge' area. |
Lateral clavicle, acromion & spine of scapula | Deltoid tuberosity of humerus | Axillary n. (C5, C6) | Abduct shoulder 15–90° (acromial part); Flex & medially rotate shoulder (clavicular part); Extend & laterally rotate shoulder (spinal part) | |
| Supraspinatus ANI 2.3 Scapular Region Rotator cuff; most often torn. Impinged under the coracoacromial arch. |
Supraspinous fossa of scapula | Greater tubercle of humerus | Suprascapular n. (C5, C6) | Initiate shoulder abduction (0–15°) | |
| Infraspinatus ANI 2.3 Scapular Region Rotator cuff. |
Infraspinous fossa of scapula | Greater tubercle of humerus | Suprascapular n. (C5, C6) | Laterally rotate shoulder | |
| Teres minor ANI 2.3 Scapular Region Rotator cuff. Why an axillary lesion weakens (but doesn't abolish) external rotation — infraspinatus still works. |
Lateral border of scapula | Greater tubercle of humerus | Axillary n. (C5, C6) | Laterally rotate shoulder | |
| Teres major ANI 2.3 Scapular Region Not rotator cuff. Its inferior border ends the axillary artery / starts the brachial. |
Inferior angle of scapula | Intertubercular sulcus of humerus | Lower subscapular n. (C5, C6) | Medially rotate shoulder; Adduct shoulder | |
| Subscapularis ANI 2.3 Scapular Region Rotator cuff; the only one on the lesser tubercle. |
Subscapular fossa | Lesser tubercle of humerus | Upper & lower subscapular nn. (C5, C6, C7) | Medially rotate shoulder |
Pectoral — anterior axioappendicular 4
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Pectoralis major ANI 2.4 Pectoral Region & Axilla Forms the clavipectoral triangle with the deltoid (cephalic v.). Adducts the lateral fragment in a clavicle fracture. |
Clavicular head: anterior medial clavicle; sternocostal head: anterior sternum & superior costal cartilages | Intertubercular sulcus of humerus | Lateral & medial pectoral nn. | Pectoral branch of thoracoacromial a. | Adduct shoulder; Medially rotate shoulder; Draw scapula anteriorly & inferiorly; Flex shoulder (clavicular head); Extend shoulder from flexed position (sternocostal head) |
| Pectoralis minor ANI 2.4 Pectoral Region & Axilla Landmark for the three parts of the axillary artery; invested by clavipectoral fascia. |
3rd–5th ribs near their costal cartilages | Coracoid process of scapula | Medial pectoral n. (C8, T1) | Stabilise scapula against thoracic wall | |
| Serratus anterior ANI 2.4 Pectoral Region & Axilla Long thoracic nerve injury (mastectomy, node dissection) → winged scapula, can't abduct past 90°. |
Lateral parts of superior ribs | Entire medial border of scapula | Long thoracic n. (C5, C6, C7) | Lateral thoracic a. | Protract scapula; Hold scapula against thoracic wall; Upwardly rotate scapula (with trapezius) |
| Subclavius ANI 2.4 Pectoral Region & Axilla |
1st rib | Inferior shaft of clavicle | Subclavian n. (n. to subclavius) (C5, C6) | Anchor/depress clavicle |
Anterior arm 3
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Biceps brachii ANI 4.1 Brachium & Elbow The arm muscle with NO humeral attachment. Powerful supinator; biceps reflex = C5–6. Long-head rupture → 'Popeye' bulge. |
Short head: coracoid process; long head: supraglenoid tubercle | Radial tuberosity & antebrachial fascia (via bicipital aponeurosis) | Musculocutaneous n. (C5, C6) | Supinate forearm; Flex supinated elbow; Flex shoulder (weak) | |
| Coracobrachialis ANI 4.1 Brachium & Elbow Pierced by the musculocutaneous nerve; median n. & brachial a. pass deep to it. |
Coracoid process | Middle humeral shaft (medial) | Musculocutaneous n. (C5, C6, C7) | Flex shoulder; Adduct shoulder | |
| Brachialis ANI 4.1 Brachium & Elbow Workhorse elbow flexor regardless of forearm position; floor of the cubital fossa (with supinator). |
Distal anterior humeral shaft | Ulnar tuberosity & coronoid process | Musculocutaneous n. (C5, C6) | Flex elbow (all positions) |
Posterior arm 2
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Triceps brachii ANI 4.1 Brachium & Elbow Lateral head strongest, medial head most active. Triceps reflex = C7–8. Essential to push out of a chair. |
Long head: infraglenoid tubercle; lateral head: superior humeral shaft; medial head: inferior humeral shaft | Olecranon | Radial n. (C6, C7, C8) | Deep brachial (profunda brachii) a. | Extend elbow; Extend shoulder (weak, long head) |
| Anconeus ANI 4.1 Brachium & Elbow |
Lateral epicondyle of humerus | Lateral olecranon & posterior ulna | Radial n. (C7, C8, T1) | Stabilise elbow; Assist elbow extension |
Anterior forearm 8
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Pronator teres ANI 4.2 Antebrachium & Wrist Median nerve passes between its two heads — pronator syndrome. |
Coronoid process & medial humeral epicondyle | Lateral proximal radius | Median n. | Pronate forearm; Flex elbow | |
| Flexor carpi radialis ANI 4.2 Antebrachium & Wrist |
Medial humeral epicondyle | 2nd metacarpal | Median n. | Flex wrist; Abduct wrist | |
| Palmaris longus ANI 4.2 Antebrachium & Wrist Absent in ~15% of people; its tendon is the landmark medial to which the median nerve enters the carpal tunnel. |
Medial humeral epicondyle | Flexor retinaculum & palmar aponeurosis | Median n. | Flex wrist; Tense palmar aponeurosis | |
| Flexor digitorum superficialis ANI 4.2 Antebrachium & Wrist Tested by flexing the PIP while the other fingers are held extended. |
Medial humeral epicondyle & anterior proximal radius | Middle phalanges of digits 2–5 | Median n. | Flex wrist; Flex MCP & PIP joints of digits 2–5 | |
| Flexor digitorum profundus ANI 4.2 Antebrachium & Wrist Dual innervation: lateral half (digits 2–3) median via AIN, medial half (digits 4–5) ulnar. Only muscle that flexes the DIP. |
Anterior ulna | Distal phalanges of digits 2–5 | Lateral half: anterior interosseous n. (median); medial half: ulnar n. | Flex wrist; Flex MCP, PIP & DIP joints of digits 2–5 | |
| Flexor pollicis longus ANI 4.2 Antebrachium & Wrist AIN lesion → can't make an 'OK' sign (FPL + lateral FDP). |
Anterior radius | Distal phalanx of thumb | Anterior interosseous n. | Flex MCP & IP joints of thumb | |
| Pronator quadratus ANI 4.2 Antebrachium & Wrist Deepest anterior forearm muscle; square, runs between the distal ulna and radius. |
Distal anterior ulna | Distal anterior radius | Anterior interosseous n. | Pronate forearm | |
| Flexor carpi ulnaris ANI 4.2 Antebrachium & Wrist Ulnar nerve passes between its two heads at the elbow — cubital tunnel. |
Medial humeral epicondyle & olecranon | Pisiform, hamate, 5th metacarpal | Ulnar n. | Flex wrist; Adduct wrist |
Posterior forearm 8
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Brachioradialis ANI 4.2 Antebrachium & Wrist A flexor in the extensor compartment; the C6 reflex. |
Lateral supracondylar ridge of humerus | Lateral distal radius | Radial n. | Flex forearm from mid-pronated position | |
| Extensor carpi radialis longus ANI 4.2 Antebrachium & Wrist |
Lateral supracondylar ridge of humerus | 2nd metacarpal | Radial n. | Extend wrist; Abduct wrist | |
| Extensor carpi radialis brevis ANI 4.2 Antebrachium & Wrist Common site of lateral epicondylitis ('tennis elbow'). |
Lateral humeral epicondyle | 3rd metacarpal | Deep radial n. | Extend wrist; Abduct wrist | |
| Extensor digitorum ANI 4.2 Antebrachium & Wrist |
Lateral humeral epicondyle | Extensor expansion of digits 2–5 | Posterior interosseous n. | Extend wrist; Extend digits 2–5 | |
| Extensor digiti minimi ANI 4.2 Antebrachium & Wrist |
Lateral humeral epicondyle | Extensor expansion of digit 5 | Posterior interosseous n. | Extend digit 5 | |
| Extensor carpi ulnaris ANI 4.2 Antebrachium & Wrist |
Lateral humeral epicondyle & posterior ulna | 5th metacarpal | Posterior interosseous n. | Extend wrist; Adduct wrist | |
| Extensor indicis ANI 4.2 Antebrachium & Wrist Lets you point with the other fingers flexed. |
Posterior distal ulna | Extensor expansion of digit 2 | Posterior interosseous n. | Extend wrist; Extend digit 2 | |
| Supinator ANI 4.2 Antebrachium & Wrist The deep radial nerve pierces it (arcade of Frohse) and emerges as the posterior interosseous n. |
Lateral humeral epicondyle, radial collateral lig., annular lig., & proximal ulna | Proximal radius | Deep radial n. | Supinate forearm |
Thenar outcropping (deep posterior forearm) 3
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Abductor pollicis longus ANI 4.2 Antebrachium & Wrist Forms the lateral border of the anatomical snuffbox with EPB. |
Posterior proximal ulna & radius | 1st metacarpal | Posterior interosseous n. | Abduct thumb at CMC joint; Extend thumb at CMC joint | |
| Extensor pollicis longus ANI 4.2 Antebrachium & Wrist Medial border of the anatomical snuffbox; hooks around Lister's tubercle. |
Posterior ulna | Distal phalanx of thumb | Posterior interosseous n. | Extend CMC, MCP & IP joints of thumb | |
| Extensor pollicis brevis ANI 4.2 Antebrachium & Wrist Lateral border of the snuffbox with APL; De Quervain tenosynovitis. |
Posterior radius | Proximal phalanx of thumb | Posterior interosseous n. | Extend CMC & MCP joints of thumb |
Hand — superficial intrinsics (thenar & hypothenar, lumbricals) 7
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Abductor pollicis brevis ANI 4.3 Hand Thenar muscle. The recurrent median branch is the 'million-dollar nerve' — superficial, easily cut. |
Flexor retinaculum, scaphoid, trapezium | 1st metacarpal (lateral) | Recurrent branch of median n. | Abduct thumb | |
| Flexor pollicis brevis ANI 4.3 Hand Thenar muscle (deep head often ulnar). |
Flexor retinaculum, scaphoid, trapezium | Proximal phalanx of thumb (lateral) | Recurrent branch of median n. | Flex thumb at CMC joint | |
| Opponens pollicis ANI 4.3 Hand Thenar muscle. Lost in carpal tunnel syndrome → 'ape hand'. |
Flexor retinaculum, scaphoid, trapezium | 1st metacarpal (lateral) | Recurrent branch of median n. | Oppose thumb | |
| Lumbricals ANI 4.3 Hand Same split as FDP: lateral (digits 2–3) median, medial (digits 4–5) ulnar. Loss → clawing. |
Tendons of flexor digitorum profundus | Extensor expansion of digits 2–5 | Lateral 2: median n.; medial 2: deep branch of ulnar n. | Flex MCP joints of digits 2–5; Extend IP joints of digits 2–5 | |
| Abductor digiti minimi ANI 4.3 Hand Hypothenar muscle. |
Pisiform | Proximal phalanx of digit 5 (medial) | Deep branch of ulnar n. | Abduct digit 5 | |
| Flexor digiti minimi brevis ANI 4.3 Hand Hypothenar muscle. The lecture table lists the action as flexion at the PIP; most texts say MCP. |
Hook of hamate & flexor retinaculum | Proximal phalanx of digit 5 (medial) | Deep branch of ulnar n. | Flex digit 5 | |
| Opponens digiti minimi ANI 4.3 Hand Hypothenar muscle. |
Hook of hamate & flexor retinaculum | 5th metacarpal (medial) | Deep branch of ulnar n. | Rotate digit 5 anterolaterally (oppose) |
Hand — deep intrinsics 3
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| Adductor pollicis ANI 4.3 Hand Froment's sign: weak adductor pollicis → thumb IP flexes (FPL substitutes) when pinching paper. |
Metacarpals 2–3 & capitate | Proximal phalanx of thumb (medial) | Deep branch of ulnar n. | Adduct thumb | |
| Dorsal interossei ANI 4.3 Hand DAB — Dorsals ABduct. Four of them; digit 3 gets two. |
Adjacent metacarpals (bipennate) | Proximal phalanx & extensor expansion of digits 2–4 | Deep branch of ulnar n. | Abduct digits 2–4; Assist lumbricals (flex MCP, extend IP) | |
| Palmar interossei ANI 4.3 Hand PAD — Palmars ADduct. Three of them (digit 3 has none). |
Metacarpals 2, 4, 5 | Proximal phalanx & extensor expansion of digits 2, 4, 5 | Deep branch of ulnar n. | Adduct digits 2, 4, 5; Assist lumbricals (flex MCP, extend IP) |
Thoracic wall & diaphragm 7
| Muscle | Proximal | Distal | Innervation | Blood supply | Action(s) |
|---|---|---|---|---|---|
| External intercostals ANI 6.1 Thoracic Wall Most active in inspiration (primary respiratory). Superficial layer. |
Inferior border of rib above | Superior border of rib below (fibres run inferoanteriorly — 'hands in pockets') | Intercostal nn. | Intercostal aa. | Elevate ribs (inspiration); Stabilise thoracic cage |
| Internal intercostals ANI 6.1 Thoracic Wall Middle layer; the neurovascular bundle (VAN, superior → inferior) runs between internal and innermost. |
Superior border of rib below | Inferior border of rib above (fibres run inferoposteriorly) | Intercostal nn. | Intercostal aa. | Depress ribs (forced expiration); Stabilise thoracic cage |
| Innermost intercostals ANI 6.1 Thoracic Wall Deepest layer; needle for thoracentesis goes over the superior border of the rib below to miss VAN. |
Superior border of rib below | Inferior border of rib above | Intercostal nn. | Intercostal aa. | Assist internal intercostals (depress ribs) |
| Subcostals ANI 6.1 Thoracic Wall Posterior thoracic wall; span more than one intercostal space; poorly developed superiorly. |
Internal surface of rib near angle | Internal surface of 2nd or 3rd rib below | Intercostal nn. | Depress ribs | |
| Transversus thoracis ANI 6.1 Thoracic Wall Deep surface of the anterior wall; the internal thoracic artery runs on it. |
Inferior sternum, xiphoid process & costal cartilages | Costal cartilages of ribs 2–6 | Intercostal nn. | Depress ribs (aid expiration) | |
| Levatores costarum ANI 6.1 Thoracic Wall The intermediate-back muscles revisited in the thorax lecture; more proprioceptive than respiratory. |
Transverse processes of C7–T11 | Rib immediately below (brevis) or second rib below (longus) | Posterior rami of spinal nn. | Elevate ribs; Proprioception | |
| Respiratory diaphragm ANI 6.1 Thoracic Wall Motor phrenic (C3–C5); sensory phrenic centrally, intercostal nn. peripherally. Phrenic injury → paradoxical movement (injured side rises). Openings: T8 IVC, T10 esophagus, T12 aorta. |
Sternal (xiphoid), costal (ribs 7–12) & lumbar (crura, arcuate ligaments) parts | Central tendon | Phrenic n. (C3, C4, C5) | Inferior phrenic aa. (and pericardiacophrenic / musculophrenic) | Primary muscle of inspiration (descends, ↑ thoracic volume) |
Sources: ANI 1.1 summary slides 26–51 and 57–89; 2.3 slide 44; 2.4 slides 13–14; 4.1 slides 30–31; 4.2 slides 47–49; 4.3 slides 23–24; 6.1 slides 12–20. Blank cells in the slides ("same as above") are filled in; the erector spinae and suboccipital attachments follow the lecture figures.