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Trapezuis
- Origin: medial 3rd of superior nuchal line external occipital protuberance, nuchal ligament, and spinous process of C7-T12 vertebrae
- Insertion: lateral 3rd of clavicle, acromion process, and spine of scapula
- Innervation: spinal accessory nerve (CN XI) and cervical nerves C3 and C4 (pain and proprioception)
- Action: superior fibers elevate, middle fibers retract, and inferior fibers depress scapula; superior and inferior fibers act together in superior rotation of scapula (inferior angle outward)
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Latissimus Dorsi
- Origin: spinous processes of inferior 6 thoracic vertebrae (T7-T12), thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs (9-12)
- Insertion: floor of intertubecular groove of humerus
- Innervation: thoracodorsal nerve (C6, C7, C8)
- Action: extends, adducts, and IR humerus; raises body toward arms during climbing
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Rhomboid Major and Minor
- Origin: Major: Spinous process of T2-T5 vertebrae (inferior to spine of scapula); Minor: spinous process of C7-T1 (superior to spine of scapula)
- Insertion: medial border of scapula from level of spine to inferior angle
- Innervation: dorsal scapular nerve (C5)
- Action: retract scapula and rotate inferior angle medially to depress glenoid cavity; fix scapula to thoracic wall
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Erector Spinae:
- Iliocostalis (lateral)
- Longissimus (middle)
- Spinalis (medial)
- Origin: iliac crest, sacrum, sacral lumbar spinous process, supraspinous ligament
- Insertion: iliocostalis: ribs and cervical transverse process; longissimus: between tubercle and angle of rib, transverse process, mastoid process; spinalis: spinous process and skull
- Innervation: dorsal rami
- Action: extensor of spine
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Sternocleidomastoid
- Origin: mastoid process
- Insertion: sternum and medial portion of clavicle
- Innervation: spinal accessory nerve (CN XI)
- Action: SB towards ipsilateral side and rotates contralateral; acting together flexes the neck and raises sternum and assists in forced inspiration
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Levator Scapulae
- Origin: posterior tubercles of transverse process of C1-C4 vertebrae
- Insertion: superior part of medial border of scapula
- Innervation: dorsal scapular (C5) and Cervical nerves (C3-C4)
- Action: elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula, also SB neck and rotate it ipsilaterally
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Scalene
(Ant, Middle, Post)
- Origin: transverse process of cervical vertebrae (C2-C7)
- Insertion: Ant -> 1st rib; Middle -> 1st rib, Post -> 2nd rib
- Innervation: C3-C8
- Action: elevates 1st and 2nd rib, SB and rotates cervical spine towards ipsilateral side
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Suboccipital Triangle
-obliquus capitis superior
-obliquus capitis inferior
-rectus capitis posterior major
-rectus capitis posterior minor
- Origin:
- -RCPMa:C2 spinous process
- -RCPMi: C1 posterior tubercle
- -OCS: C1 Transverse process
- -OCI: C2 spinous process
- Insertion:
- -RCPMa: lateral part of inferior nuchal line
- -RCPMi: medial part of inferior nuchal line
- -OCS: occiput
- -OCI: C1 transverse process
- Innervation: dorsal ramus of C1 (suboccipital nerve)
- Action: extends occiput on C1 (OA extension); rotates C1 on C2
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Deltoid
- Origin: lateral 3rd of clavicle, acromion, and spine of scapula
- Insertion: deltoid tuberosity of humerus
- Innervation: axillary nerve (C5 and C6)
- Action: ant portion-> flexes and IR arm; middle portion-> abducts arm; posterior portion-> extends and ER arm
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Supraspinatus
- Origin: supraspinous fossa of scapula
- Insertion: superior facet on greater tubercle of humerus
- Innervation: suprascapular nerve (C4, C5, C6)
- Action: initiates and assists deltoid in abduction of arm and acts with rotator cuff muscles
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Infraspinatus
- Origin: infraspinatus fossa of scapula
- Insertion: middle facet on greater tubercle of humerus
- Innervation: suprascapular nerve (C5-C6)
- Action: ER; help to hold humeral head in glenoid cavity of scapula; depress humeral head
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Teres Minor
- Origin: superior part of lateral border of scapula
- Insertion: inferior facet on greater tunercle on humerus
- Innervation: axillary nerve (C5-C6)
- Action: ER; help to hold humeral head in glenoid cavity of scapula; depress humeral head
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Subscapularis
- Origin: subscapular fossa
- Insertion: lesser tubercle of humerus
- Innervation: upper and lower subscapular nerve (C5, C6, C7)
- Action: IR and adducts humerus; help to hold humeral head in glenoid cavity of scapula
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Teres Major
- Origin: dorsal surface of inferior angle of scapula
- Insertion: Medial lip of intertubercular groove of humerus
- Innervation: lower subscapular nerve (C6-C7)
- Action: adducts and IR arm
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Pectoralis Major
- Origin: clavicular head -> anterior surface of medial half of clavicle; sternocostal head -> anterior surface of sternum, superior 6 costal cartilages, and aponeurosis of external oblique muscle
- Insertion: lateral lip of intertubercular groove of humerus
- Innervation: lateral and medial pectoral nerves, clavicular head (C5-C6), sternocostal head (C7, C8, T1)
- Action: adducts and IR humerus; draws scapula anteriorly and inferiorly; acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed position
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Pectoralis Minor
- Origin: 3rd-5th ribs near costal cartilages
- Insertion: medial border and superior surface of coracoid process of scapula
- Innervation: medial pectoral nerve (C8-T1)
- Action: stabilizes scapula by drawing it inferiorly and anteriorly against thoracic wall (protraction and depression of scapula)
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Subclavius
- Origin: junction of 1st rib and its costal cartilage
- Insertion: inferior surface of middle 1/3 of clavicle
- Innervation: nerve to subclavius (C5-C6)
- Action: Protracts scapula and holds it against thoracic wall; rotates scapula
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Serratus Anterior
- Origin: external surfaces of lateral parts of ribs 1-8
- Insertion: anterior surface of medial border of scapula
- Innervation: long thoracic nerve (C5, C6, C7)
- Action: protracts scapula and holds it against thoracic wall; rotates scapula (inferior angle laterally) = stabilizes
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Bicep Brachii
- Origin: short head -> tip of coracoid process of scapula; long head -> supraglenoid tubercle of scapula
- Insertion: tuberosity of radius and fascia of forearm via bicipital aponeurosis
- Innervation: musculocutaneous nerve (C5-C6)
- Action: Supinates forearm, flexes forearm, flexes shoulder
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Brachialis
- Origin: distal half of anterior surface of humerus
- Insertion: coronoid process and tuberosity of ulna
- Innervation: musculocutaneous nerve (C5-C6)
- Action: flexes forearm in all positions
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Coracobrachialis
- Origin: tip of coracoid process of scapula
- Insertion: middle third of medial surface of humerus
- Innervation: musculocutaneous nerve (C5, C6, C7)
- Action: flexes and adducts arm
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Triceps Brachii
- Origin: long head -> infraglenoid tubercle of scapula; lateral head -> posterior surface of humerus, superior to radial groove; medial head -> posterior surface of humerus, inferior to radial groove
- Insertion: proximal end of olecranon of ulna and fascia of forearm
- Innervation: radial nerve (C6, C7, C8)
- Action: extends the forearm; it is the chief extensor of forearm and extends the arm
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Anconeus
- Origin: lateral epicondyle of humerus
- Insertion: lateral surface of olecranon and superior part of posterior surface of ulna
- Innervation: radial nerve (C7-C8)
- Action: assists triceps in extending the forearm
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Brachioradialis (1st layer)
- Origin: proximal 2/3 of lateral supracondylar ridge of humerus
- Insertion: lateral surface of the distal end of the radius
- Innervation: radial nerve (C5, C6, C7)
- Action: flexes forearm w/ thumb up (neutral position)
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Pronator Teres (1st layer)
- Origin: distal supracondylar ridge and medial epicondyle of humerus (humeral/superficial head) and coronoid process of ulna (ulnar/deep head)
- Insertion: middle of lateral surface of radius
- Innervation: median nerve (C6-C7)
- Action: pronates and flexes forearm @ elbow
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Flexor Carpi Radialis (1st layer)
- Origin: medial epicondyle of humerus
- Insertion: base of 2nd metacarpal bone
- Innervation: median nerve (C6-C7)
- Action: flexes and abducts (radial deviates) hand @ wrist
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Palmaris Longus (1st layer)
- Origin: medial epicondyle of humerus
- Insertion: distal 1/2 of the flexor retinaculum and palmar aponeurosis
- Innervation: medial nerve (C7-C8)
- Action: flexes hand (@ wrist) and tightens palmar aponeurosis; minor contribution (14-20% of people lack this muscle)
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Flexor Carpi Ulnaris (1st layer)
- Origin: humeral head -> medial epicondyle of humerus; ulnar head -> olecranon and posterior border of ulna
- Insertion: pisiform bone, hook of hamate bone, and 5th metacarpal
- Innervation: ulnar nerve (C7-C8)
- Action: flexes and adducts (ulnar deviation) hand @ wrist
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Flexor Digitorum Superficialis (2nd layer)
- Origin: humeroulnar head -> medial epicondyle of humerus, ulnar collateral ligament, and coronoid process of ulna; radius -> superior 1/2 of anterior border of radius
- Insertion: bodies of middle phalanges of medial 4 digits
- Innervation: median nerve (C7, C8, T1)
- Action: flexes PIP joint
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Flexor Digitorum Profundus (3rd layer)
- Origin: proximal 3/4 of medial and anterior surfaces of ulna and interosseous membrane
- Insertion: bases of distal phalanx of medial four digits
- Innervation: medial part -> ulnar nerve (C8-T1); lateral part -> median nerve (C8-T1) ---> anterior interosseous nerve
- Action: flexes DIP 2 distal interphalangeal joints of medial 4 digits; assists with flexion of hand
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Flexor Pollicis Longus (3rd layer)
- Origin: anterior surface of radius and adjacent interosseous membrance
- Insertion: bases of distal phalanx of thumb
- Innervation: anterior interosseous nerve from median (C8-T1)
- Action: flexes phalanx of 1st digit (thumb)
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Pronator Quadratus (4th layer)
- Origin: distal fourth of anterior surface of ulna
- Insertion: distal fourth of anterior surface of radius
- Innervation: anterior interosseous nerve from median (C8-T1)
- Action: pronates forearm; deep fibers bind radius and ulna together
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Supinator
- Origin: lateral epicondyle of humerus, radial collateral and anular ligaments, supinator fossa, and crest of ulna
- Insertion: lateral, posterior, and anterior surfaces of proximal third of radius
- Innervation: deep branch of radial nerve (C5-C6)
- Action: supinates forearm (rotates radius to turn palm anteriorly)
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Extensor Carpi Radialis Longus
- Origin: lateral supracondylar ridge of humerus (below brachioradialis)
- Insertion: base of 2nd metacarpal
- Innervation: radial nerve (C6-C7)
- Action: extend and abduct (radial deviate) hand at wrist joint
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Extensor Carpi Radialis Brevis
- Origin: lateral epicondyle of humerus
- Insertion: base of 3rd metacarpal
- Innervation: deep branch of radial nerve (C7-C8)
- Action: extend hand at wrist joint
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Extensor Carpi Ulnaris
- Origin: lateral epicondyle of humerus and posterior border of ulna
- Insertion: base of 5th metacarpal
- Innervation: posterior interosseous nerve (C7-C8), the continuation of the deep branch of radial nerve
- Action: extends and adducts (ulnar deviation) hand at wrist joint
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Extensor Digitorum
- Origin: lateral epicondyle of humerus
- Insertion: extensor expansions of medial four digits
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: extends medial four digits at metacarpophalangeal joints; extends hand at wrist joint
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Extensor Digiti Minimi
- Origin: lateral epicondyle of humerus
- Insertion: extensor expansion of 5th digit
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: extends 5th digit at metacarpophalangeal and interphalangeal joints
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Abductor Pollicis Longus
- Origin: posterior surfaces of ulna, radius and interosseous membrane
- Insertion: base of 1st metacarpal
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: Abducts thumb and extends it at carpometacarpal joint (snuff box)
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Extensor Pollicis Brevis
- Origin: posterior surface of radius and interosseous membrance
- Insertion: base of proximal phalanx of thumb
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: extends proximal phalanx of thumb at carpometacarpal joint (snuff box)
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Extensor Pollicis Longus
- Origin: posterior surface of middle third of ulna and interosseous membrane
- Insertion: base of distal phalanx of thumb
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: extends distal phalanx of thumb at metacarpophalangeal and interphalangeal joints (snuff box)
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Extensor Indicis
- Origin: posterior surface of ulna and interosseous membrane
- Insertion: extensor expansion of 2nd digit
- Innervation: posterior interosseous nerve (C7-C8), the continuation of deep branch of radial nerve
- Action: extends 2nd digit and helps to extend hand
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Opponens Digiti Minimi (hypothenar muscles)
- Origin: hook of hamate and flexor retinaculum
- Insertion: medial border fo 5th metacarpal
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: draws 5th metacarpal anteriorly and rotates it, bringing digit 5 into opposition with thumb
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Flexor Digiti Minimi Brevis (hypothenar muscles)
- Origin: hook of hamate and flexor retinaculum
- Insertion: medial side of base of proximal phalanx of little finger (5th digit)
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: flexes proximal phalanx of 5th digit
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Abductor Digiti Minimi (hypothenar muscles)
- Origin: pisiform
- Insertion: medial side of base of phalanx of little finger
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: abducts 5th digit
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Adductor Pollicis
- Origin: oblique head -> bases of 2nd and 3rd metacarpals, capitate, and adjacent carpals; transverse head -> anterior surface of body of 3rd metacarpal
- Insertion: medial side of bases of proximal phalanx of thumb
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: adducts thumb toward middle digit
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Flexor Pollicis Brevis (thenar muscles)
- Origin: flexor retinaculum and tubercles of scaphoid and trapezium
- Insertion: lateral side of base of proximal phalanx of thumb
- Innervation: recurrent branch of median nerve (C8-T1)
- Action: flexes thumb
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Opponens Pollicis (thenar muscles)
- Origin: flexor retinaculum and tubercles of scaphoid and trapezium
- Insertion: lateral side of 1st metacarpal
- Innervation: recurrent branch of median nerve (C8-T1)
- Action: draws 1st metacarpal bone medially to oppose thumb toward center of palm and rotates it medially
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Abductor Pollicis Brevis (thenar muscles)
- Origin: flexor retinaculum and tubercles of scaphoid and trapezium
- Insertion: lateral side of base of proximal phalanx of thumb
- Innervation: recurrent branch of median nerve (C8-T1)
- Action: abducts thumb and helps oppose it
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Palmar Interossei 1-3 (PAD)
- Origin: palmar surfaces of 2nd, 4th, and 5th metacarpals (unipennate muscles)
- Insertion: extensor expansions of digits and bases of proximal phalanges of digits 2,4 and 5
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: adduct digits toward axial line and act with lumbricals to flex MCP joints and extend interphalangeal joints
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Dorsal Interossei 1-4 (DAB)
- Origin: adjacent sides of two metacarpals (bipennate muscles)
- Insertion: extensor expansions and bases of proximal phalanges of digits 2-4
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: abducts digits from axial line and act with lumbricals to flex MCP joints and extend interphalangeal joints
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Lumbricals 1 and 2
- Origin: lateral two tendons of flexor digitorum profundus (unipennate muscles)
- Insertion: lateral sides of extensor expansions of digits 2-5
- Innervation: median nerve (C8-T1)
- Action: flexes digits at MCP joints and extend interphalangeal joints
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Lumbricals 3 and 4
- Origin: medial three tendons of flexor digitorum profundus (unipennate muscles)
- Insertion: lateral sides of extensor expansions of digits 2-5
- Innervation: deep branch of ulnar nerve (C8-T1)
- Action: flexes digits MCP joints and extend interphalangeal joints
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Rectus Abdominis
- Origin: pubic symphysis and pubic crest
- Insertion: xiphoid processes and the costal cartilages of ribs 5-7
- Innervation: intercostal nerves from T6-T11, subcostal nerve (T12); T6-T12
- Action: forward flexion of the trunk, posterior tilting of the pelvis, stabilization of the pelvis and trunk, flattening of the abdomen, supports abdominal viscera, increase intra-abdominal pressure
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External Oblique
- Origin: external surfaces of 5th-12th ribs
- Insertion: linea alba, pubic tubercle, and anterior half of iliac crest
- Innervation: thoracoabdominal nerve (inferior 6 thoracic nerves and subcostal nerve)
- Action: compress and support abdominal viscera and flex and rotate trunk
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Internal Oblique
- Origin: thoracolumbar fascia (TLF), anterior 2/3 of ilial crest, and lateral 1/2 of inguinal ligament
- Insertion: inferior borders of 10th-12th ribs, linea alba, the pecten pubis via conjoint tendon
- Innervation: thoracoabdominal (ventral rami of inferior 6 thoracic) and 1st lumbar nerves
- Action: compress and support abdominal viscera, flex and rotate trunk
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Transversus Abdominis
- Origin: internal surfaces of 7th-12th costal cartilages, thoracolumbar fascia, iliac crest, and lateral third of inguinal ligament
- Insertion: linea alba with aponeurosis of internal obliques, pubic crest, and pecten pubis via conjoint tendon
- Innervation: thoracoabdominal (ventral rami of inferior 6 thoracic) and first lumbar nerves
- Action: compresses and supports abdominal viscera
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Multifidus (lumborum)
- Origin: posterior sacrum, posterior superior iliac spine, posterior sacroiliac ligament, mammillary processes from L1-L5
- Insertion: spinous processes of vertebrae 1-4 levels superior to vertebrae of origin
- Innervation: dorsal rami of lumbar spinal nerves crossed by muscle
- Action: extends (bilaterally), controls lateral flexion and rotates (contralateral side) the lumbar spine
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