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UPPER LIMB

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SHOULDER MUSCLES

  • Can be categorized into
  • Extrinsic shoulder muscles
  • Intrinsic shoulder muscles

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EXTRINSIC SHOULDER MUSCLES

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TRAPEZIUS

  • ORIGIN: Medial third of superior nuchal line; external occipital protuberance; nuchal ligament; spinous processes of C7–T12 vertebrae
  • INSERTION: Lateral third of clavicle; acromion and spine of scapula
  • INNERVATION: Spinal accessory nerve (CN XI) (motor fibers) and C3, C4 spinal nerves (pain and proprioceptive fibers)
  • ACTION: Descending part elevates; ascending part depresses; and middle part (or all parts together) retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorly

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Latissimus dorsi

  • ORIGIN: Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs
  • INSERTION: Floor of intertubercular sulcus of humerus
  • INNERVATION: Thoracodorsal nerve (C6, C7, C8)
  • ACTION: Extends, adducts, and medially rotates humerus; raises body toward arms during climbing

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Levator scapulae

  • ORIGIN: Posterior tubercles of transverse processes of C1–C4 vertebrae
  • INSERTION: Medial border of scapula superior to root of scapular spine
  • INNERVATION: Dorsal scapular (C5) and cervical (C3, C4) nerves
  • ACTION: Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula

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Rhomboid minor and major

  • ORIGIN: Minor: nuchal ligament; spinous processes of C7 and T1 vertebrae; Major: spinous processes of T2–T5 vertebrae
  • INSERTION: Minor: smooth triangular area at medial end of scapular spine; Major: medial border of scapula from level of spine to inferior angle
  • INNERVATION: Dorsal scapular nerve (C4, C5)
  • ACTION: Retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wall

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INTRINSIC SHOULDER MUSCLES

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TERES MINOR

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ROTATOR CUFF MUSCLES

  • The tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles are fused to the underlying capsule of the shoulder joint.
  • Because of this relationship, these four muscles are referred to as the “rotator cuff.” The cuff plays a very important role in stabilizing the glenohumeral (shoulder) joint.
  • The tone of these muscles assists in holding the head of the humerus in the glenoid cavity of the scapula during movements at the shoulder joint..

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MUSCLES OF THE ARM

  • Of the four major arm muscles, three flexors (biceps brachii, brachialis, and coracobrachialis) are in the anterior (flexor) compartment, supplied by the musculocutaneous nerve, and one extensor (triceps brachii) is in the posterior compartment, supplied by the radial nerve

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BICEPS BRACHII

  • Action:
  • Flex and supinate the
  • forearm
  • Nerve supply: musculocutaneous nerve
  • Origin:
  • Short head — goes to the corocoid process of scapula
  • Long head-supraglenoid
  • tubercle of scapula.

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  • Insertion:
  • radiotuberocity and
  • fascia of forearm
  • Innervation: radial nerve

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BRACHIALIS

  • Action:
  • Flexes forearm
  • Nerve supply: musculocutaneous nerve
  • Origin:
    • The distal anterior surface of the humerus.
  • Insertion:
    • The coronoid process of the ulna

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CORACOBRACHIALIS

  • Origin: Tip of coracoid process of scapula
  • Insertion: Middle third of medial surface of humerus
  • Nerve supply: musculocutaneous nerve
  • Action : Helps flex and adduct arm; resists dislocation of shoulder

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POSTERIOR COMPARTMENT

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: Chief extensor of forearm; long head resists dislocation of humerus; especially important during adduction

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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, T1)
  • ACTION: Assists triceps in extending forearm; stabilizes elbow joint; may abduct ulna during pronation

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MUSCLES OF THE FOREARM

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INTRODUCTION

  • The forearm is divided into two compartments:
  • Anterior compartment: contains flexor and pronator muscles, divided into superficial, middle and deep layer
  • Posterior compartment: contains extensor muscles, divided into superficial and deep layer

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ANTERIOR-SUPERFICIAL MUCLES

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PRONATOR TERES

  • Has two heads; ulnar and humeral head
  • ORIGIN: coronoid process
  • INSERTION: middle of convexity of lateral surface of radius
  • INNERVATION: MEDIAN NERVE
  • ACTION: Pronates and flexes forearm at elbow

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Flexor carpi radialis (FCR)

  • ORIGIN: Medial epicondyle of humerus (common flexor origin)
  • INSERTION: Base of 2nd metacarpal
  • INNERVATION: Median nerve (C6, C7)
  • ACTION: Flexes and abducts hand (at wrist)

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PALMARIS LONGUS

  • ORIGIN: Medial epicondyle of humerus (common flexor origin)
  • INSERTION: Distal half of flexor retinaculum and apex of palmar aponeurosis
  • INNERVATION: Median nerve (C7, C8)
  • ACTION: Flexes hand (at wrist) and tenses palmar aponeurosis

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Flexor carpi ulnaris (FCU)

  • ORIGIN:
  • Humeral head: Medial epicondyle of humerus (common flexor origin)
  • Ulnar head: Olecranon and posterior border (via aponeurosis)
  • INSERTION: Pisiform, hook of hamate, 5th metacarpal
  • INNERVATION: Ulnar nerve (C7, C8)
  • ACTION: Flexes and adducts hand (at wrist)

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ANTERIOR-INTERMEDIATE MUSCLE

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Flexor digitorum superficialis (FDS

  • ORIGIN:
  • Humeroulnar head: Medial epicondyle (common flexor origin and coronoid process)
  • Radial head: Superior half of anterior border
  • INSERTION: Shafts of middle phalanges of medial four digits
  • INNERVATION: Median nerve (C7, C8, T1)
  • ACTION: Flexes middle phalanges at proximal interphalangeal joints of middle four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints

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ANTERIOR-DEEP MUSCLES

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Flexor digitorum profundus (FDP)

MEDIAL PART

  • ORIGIN: Proximal three quarters of medial and anterior surfaces of ulna and interosseous membrane
  • INSERTION: Bases of distal phalanges of 4th and 5th digits
  • INNERVATION: Ulnar nerve (C8, T1)
  • ACTION: Flexes distal phalanges 4 and 5 at distal interphalangeal joints

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Flexor digitorum profundus (FDP)…

LATERAL PART

  • ORIGIN: Proximal three quarters of medial and anterior surfaces of ulna and interosseous membrane
  • INSERTION: Bases of distal phalanges of 2nd and 3rd digits
  • INNERVATION: Ulnar nerve (C8, T1)
  • ACTION: Flexes distal phalanges 2 and 3 at distal interphalangeal joints

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Flexor pollicis longus (FPL)

  • ORIGIN: Anterior surface of radius and adjacent interosseous membrane
  • INSERTION: Base of distal phalanx of thumb
  • INNERVATION: Anterior interosseous nerve, from median nerve (C8, T1)
  • ACTION: Flexes phalanges of 1st digit (thumb)

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Pronator quadratus

  • ORIGIN: Distal quarter of anterior surface of ulna
  • INSERTION: Distal quarter of anterior surface of radius
  • INNERVATION: Anterior interosseous nerve, from median nerve (C8, T1
  • ACTION: Pronates forearm; deep fibers bind radius and ulna together

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EXTENSOR MUSCLES

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INTRODUCTION

  • The posterior compartment contains the extensor muscles of the forearm, brachioradialis and supinator.
  • The superficial posterior muscles include, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris.
  • The deep posterior group of muscles includes supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis.

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SUPERFICIAL EXTENSOR MUSCLES

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Brachioradialis

  • ORIGIN: Proximal two thirds of supraepicondylar ridge of humerus
  • INSERTION: Lateral surface of distal end of radius proximal to styloid process
  • INNERRVATION: Radial nerve (C5, C6, C7)
  • ACTION: Relatively weak flexion of forearm; maximal when forearm is in midpronated position

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Extensor carpi radialis longus (ECRL)

  • ORIGIN: Lateral supraepicondylar ridge of humerus
  • INSERTION: Dorsal aspect of base of 2nd metacarpal
  • INNERVATION: Radial nerve (C6, C7)
  • ACTION: Extend and abduct hand at the wrist joint; ECRL active during fist clenching

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Extensor carpi radialis brevis (ECRB)

  • ORIGIN: Lateral epicondyle of humerus (common extensor origin)
  • INSERTION: Dorsal aspect of base of 3rd metacarpal
  • INNERVATION: Deep branch of radial nerve (C7, C8)
  • ACTION: Extend and abduct hand at the wrist joint; ECRL active during fist clenching

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Extensor digitorum

  • ORIGIN: Lateral epicondyle of humerus; posterior border of ulna via a shared aponeurosis
  • INSERTION: Extensor expansions of medial four digits
  • INNERVATION: Deep branch of radial nerve (C7, C8)
  • ACTION: Extends medial four digits primarily at metacarpophalangeal joints, secondarily at interphalangeal joints

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Extensor digiti minimi (EDM)

  • ORIGIN: Lateral epicondyle of humerus (common extensor origin)
  • INSERTION: Extensor expansion of 5th digit
  • INNERVATION: Deep branch of radial nerve (C7, C8)
  • ACTION: Extends 5th digit primarily at metacarpophalangeal joint, secondarily at interphalangeal joint

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Extensor carpi ulnaris (ECU)

  • ORIGIN: Lateral epicondyle of humerus; posterior border of ulna via a shared aponeurosis
  • INSERTION: Dorsal aspect of base of 5th metacarpal
  • INNERVATION: Deep branch of radial nerve (C7, C8)
  • ACTION: Extends and adducts hand at wrist joint (also active during fist clenching)

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DEEP EXTENSOR MUSCLES

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Supinator

  • ORIGIN: Lateral epicondyle of humerus; radial collateral and anular ligaments; supinator fossa; crest of ulna
  • INSERTION: Lateral, posterior, and anterior surfaces of proximal third of radius
  • INNERVATION: Deep branch of radial nerve (C7, C8)
  • ACTION: Supinates forearm; rotates radius to turn palm anteriorly or superiorly (if elbow is flexed)

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Extensor indicis

  • ORIGIN: Posterior surface of distal third of ulna and interosseous membrane
  • INSERTION: Extensor expansion of 2nd digit
  • INNERVATION: Posterior interosseous nerve (C7, C8), continuation of deep branch of radial nerve
  • ACTION: Extends 2nd digit (enabling its independent extension); helps extend hand at wrist

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Abductor pollicis longus (APL)

  • ORIGIN: Posterior surface of proximal halves of ulna, radius, and interosseous membrane
  • INSERTION: Base of 1st metacarpal
  • INNERVATION: Posterior interosseous nerve (C7, C8), continuation of deep branch of radial nerve
  • ACTION: Abducts thumb and extends it at carpometacarpal joint

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Extensor pollicis longus (EPL)

  • ORIGIN: Posterior surface of middle third of ulna and interosseous membrane
  • INSERTION: Dorsal aspect of base of distal phalanx of thumb
  • INNERVATION: Posterior interosseous nerve (C7, C8), continuation of deep branch of radial nerve
  • ACTION: Extends distal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joints

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Extensor pollicis brevis (EPB)

  • ORIGIN: Posterior surface of distal third of radius and interosseous membrane
  • INSERTION: Dorsal aspect of base of proximal phalanx of thumb
  • INNERVATION: Posterior interosseous nerve (C7, C8), continuation of deep branch of radial nerve
  • ACTION: Extends proximal phalanx of thumb at metacarpophalangeal joint; extends carpometacarpal joint

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MUSCLES OF HAND

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INTRODUCTION

The intrinsic muscles of the hand are located in five compartments:

1. Thenar muscles in the thenar compartment.

2. Adductor pollicis in the adductor compartment.

3. Hypothenar muscles in the hypothenar compartment.

4. Short muscles of the hand, the lumbricals, in the central compartment with the long flexor tendons.

5. The interossei in separate interosseous compartments between the metacarpals

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THENAR MUSCLES

  • Abductor pollicis brevis (APB)
  • Opponens pollicis (OPP)
  • Flexor pollicis brevis (FPB)
  • Adductor pollicis (ADD)

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THENAR MUSCLES…

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HYPOTHENAR MUSCLES

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HYPOTHENAR MUSCLES

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HYPOTHENAR MUSCLES

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LUMBRICALS

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Muscle

ORIGIN

INSERTION

INNERVATION

ACTION

1st and 2nd

Lateral two tendons of flexor digitorum profundus (as unipennate muscles)

Lateral sides of extensor expansions of 2nd–5th digits

Median nerve (C8, T1)

Flex metacarpophalangeal joints; extend interphalangeal joints of 2nd–5th digits

3rd and 4th

Medial three tendons of flexor digitorum profundus (as bipennate muscles)

Lateral sides of extensor expansions of 2nd–5th digits

Median nerve (C8, T1)

Flex metacarpophalangeal joints; extend interphalangeal joints of 2nd–5th digits

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LUMBRICALS

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INTEROSSIE MUSCLES

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MUSCLES

ORIGIN

INSERTION

INNERVATION

ACTION

Dorsal interossei, 1st–4th

Adjacent sides of two metacarpals (as bipennate muscles)

Bases of proximal phalanges; extensor expansions of 2nd–4th digits

Deep branch of ulnar nerve (C8, T1)

Abduct 2nd–4th digits from axial line

Palmar interossei, 1st–3rd

Palmar surfaces of 2nd, 4th, and 5th metacarpals (as unipennate muscles)

Bases of proximal phalanges; extensor expansions of 2nd, 4th, and 5th digits

Deep branch of ulnar nerve (C8, T1)

Adduct 2nd, 4th, and 5th digits toward axial line

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INTEROSSIE MUSCLES …

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CLINICAL CORRELATES

  • RADIAL NERVE INJURY

Injury to the radial nerve superior to the origin of its branches to the triceps brachii results in paralysis of the triceps, brachioradialis, supinator, and extensor muscles of the wrist and fingers. Loss of sensation in areas of skin supplied by this nerve also occurs. . The characteristic clinical sign of radial nerve injury is wrist-drop

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BICEPS TENDINITIS

  • The tendon of the long head of the biceps is enclosed by a synovial sheath and moves back and forth in the intertubercular sulcus of the humerus. Wear and tear of this mechanism can cause shoulder pain. Inflammation of the tendon (biceps tendinitis), usually the result of repetitive microtrauma, is common in sports involving throwing (e.g., baseball and cricket) and use of a racquet (e.g., tennis)

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Paralysis of Serratus Anterior

  • When the serratus anterior is paralyzed owing to injury to the long thoracic nerve, the medial border of the scapula moves laterally and posteriorly away from the thoracic wall, giving the scapula the appearance of a wing, especially when the person leans on a hand or presses the upper limb against a wall. When the arm is raised, the medial border and inferior angle of the scapula pull markedly away from the posterior thoracic wall, a deformation known as a winged scapula.

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