Upper Limb Compartments Arm Muscles PDF

Upper Limb Compartments Arm Muscles Arm Compartments - Arm = divided into ANTERIOR + POSTERIOR compartments by extensions of deep fascia called medial + lateral intermuscular space o ANTERIOR/FLEXOR: occupied by flexor muscles (biceps brachii, coracobrachialis and brachialis) + innervated via musculo...

Upper Limb Compartments Arm Muscles Arm Compartments - Arm = divided into ANTERIOR + POSTERIOR compartments by extensions of deep fascia called medial + lateral intermuscular space o ANTERIOR/FLEXOR: occupied by flexor muscles (biceps brachii, coracobrachialis and brachialis) + innervated via musculocutaneous nerve § Flexion of arm at shoulder § Flexion of forearm at elbow § SupinaOon of forearm o POSTERIOR/EXTENSOR: occupied by extensor muscle (triceps brachii) + innervated via radial nerve § Extension of arm @ shoulder § Extension of forearm @ elbow Anterior Compartments Muscle Origin + InserOon FuncOon InnervaOon Picture BICEPS BRACHII Origin - Flexion of arm @ shoulder - Musculocutaneous nerve Short head: coracoid process - Flexion of forearm - Origin from C5, C6, C7 roots FLEXION + SUPINATION of scapula (only palpable - SupinaOon of forearm - Terminal branch of lateral point) cord Long head: supraglenoid tubercle of scapula InserOon - Radial tuberosity (permits movement for supinaOon) + fascia of forearm via bicipital aponeurosis CORACOBRACHIALIS Origin - Flexion of arm - Musculocutaneous nerve (sweeps under biceps + only Coracoid process of scapula - AdducOon of arm (especially - Origin from C5, C6, C7 roots crosses the shoulder joint, InserOon in the horizontal adducOon = - Terminal branch of lateral thus will only work on the Middle third of medial surface transverse plane) cord shoulder) of humerus BRACHIALIS FLEXION + PRONATION Origin Distal half of anterior surface of humerus InserOon - Ulnar tuberosity - Coronoid process of ulna (no movement permi[ed) - Flexion of arm - Musculocutaneous nerve - Origin from C5, C6, C7 roots - Terminal branch of lateral cord Posterior Compartments: one muscle innervated by radial nerve TRICEPS BRACHII Origin - Extension of forearm - Radial nerve Long head: infraglenoid - Extension of arm (long head - Origin from C5, 6, 7, 8 and T1 tubercle (crosses tubercle) only) roots Lateral head: lateral, posterior - Terminal branch of posterior humerus (superior to radial cord groove) Medial head: posterior surface of humerus (inferior to radial groove) InserOon Olecranon process of ulna Forearm Compartments - Tendons of forearm muscles pass through distal part of forearm à into hand - Radius, ulna, interosseous membrane connecOng them, and intermuscular septum = divide into anterior (flexor-pronator) and posterior (extensor-supinator) compartment - ANTERIOR COMPARTMENTS: flexion + pronaOon - POSTERIOR COMPARTMENTS: extension + supinaOon Anterior: Flexor-Pronator Muscles - Arise from medial epicondyle of humerus via common flexor tendon o Tendons of most flexor muscles pass across anterior surface of wrist + held by flexor reOnaculum - Muscles are divided into 3 layers: 1. SUPERFICIAL LAYER: pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris = median nerve a. Flexion of wrist b. PronaOon of forearm 2. INTERMEDIATE LAYER: flexor digitorum superficialis (FDS) = median nerve a. Flexion of digits 2-5 at MCP and PIP joints 3. DEEP LAYER: flexor digitorum profundus, flexor pollicis longus, pronator quadratus a. Flexion of thumb joints (digit 1) = median nerve b. Flexion of digits 2-5 all joints i. Digits 2 and 3 = median nerve ii. Digits 4 and 5 = ulnar nerve - All are innervated via median nerve, except FCU + medial half of FDP which are innervated via ulnar nerve - FuncOons: o If tendons cross wrist = flexion of wrist o If tendons cross phalangeal joints = flexion of digits o PronaOon of forearm Posterior: Extensor-Supinator Muscles - Organized into superficial and deep layers o Most superficial extensor muscles originate from lateral epicondyle of humerus via common extensor tendon (on lateral epicondyle) o Deep muscles mainly arise from posterior ulna, radius and interosseous membrane - All extensor muscles = innervated via radial nerve - - - Brachioradialis = innervated by radial nerve BUT is a flexor muscle SUPERFICIAL LAYER: o Brachioradialis (flexes forearm @ elbow) o Extensor carpi radialis longus + brevis (produce wrist extension and abducOon; radial deviaOon) o Extensor digitorum (extends thumb) o Extensor digit minimi (extends pinky) o Extensor carpi ulnaris (xtends carpus on ulna) o Anconeus (elbow adductor, elbow extensor and forearm supinator) DEEP LAYER: o Supinator (helps biceps) o Abductor pollicis longus (abducts thumb) o Extensor pollicis longus and brevis (extend thumb) o Extensor indicis (extends index finger) FuncOons: o SupinaOon of forearm o If muscle crosses wrist = EXTENSION of wrist o If muscle crosses digits = EXTENSION of digits Brachioradialis – BEER DRINKING MUSCLE - Distal humerus à distal radius - Anterolateral forearm muscle - FuncOons: flexion of elbow in ‘mid-pronaOon’ (beer drinking) - Nerve innervaOon: RADIAL NERVE o If a paOent injures musculocutaneous nerve will they sOll be able to perform flexion at the forearm? à YES, because radial nerve is sOll intact Muscles + Nerves of Upper Limb 1. Flexion with SupinaOon (biceps curl): biceps + musculocutaneous nerve 2. Flexion with PronaOon (barbell curl): brachialis + musculocutaneous nerve 3. Flexion in mid-pronaOon (hammer curl): brachioradialis + radial nerve ReOnacula - Forearm (antebrachial) fascia invests forearm muscles o Fascia thickens posteriorly over distal ends of radius and ulna to form a transverse band, extensor reOnaculum, which retains extensor tendons in place o Fascia thickens anteriorly to form flexor reOnaculum, which converts anterior concavity of carpus (wrist bones) into carpal tunnel through which flexor tendons + median nerve pass - ReOnacula prevent bowstringing of the tendons when the hand flexed or hyperextended at wrist joint - As extensor tendons pass over dorsum of wrist, they are invested by synovial sheaths which reduce fricOon between extensor tendons + bones Muscles of Anterior Forearm - Flexor – Pronator - Median and/or Ulnar Nerve Superficial Layer Muscle PRONATOR TERES (PT) *Impeachment of median nerve between two heads of PT; pronator syndrome* - Any muscle overworked = hypertrophic = gets thicker - PronaOon syndrome = loss of nerve funcOon FLEXOR CARPI RADIALIS (FCR) *Radial artery pulse* *Does not pass through carpal tunnel, is on the lateral side of the flexor reOnaculum* PALMARIS LONGUS (PL) *Crosses the wrist* *Absent in 12-20% of populaOon* FLEXOR CARPI ULNARIS (FCU) *Flexes carpus on ulnar side* *Only muscle in superficial layer innervated by Ulnar nerve *Course of ulnar nerve between its 2 heads* Origin + InserOon Origin Humeral head: medial epicondyle of humerus (via common flexor tendon) Ulnar head: coronoid process of ulna InserOon Middle of lateral surface of radius Origin Medial epicondyle of humerus (via common flexor tendon) InserOon Base of 2nd and 3rd metacarpals FuncOon - PronaOon of forearm - (Weakly) flexion of forearm = important for bringing food to mouth InnervaOon - Median nerve (C6, C7) - Flexion of wrist - Flexion of forearm (weak) – elbow - AbducOon (radial deviaOon) of hand - Median nerve (C6, C7) Origin Medial epicondyle of humerus (via common flexor tendon) InserOon - Palmar aponeurosis - Flexor reOnaculum - Flexion of head - Flexion of forearm (weak) - Median nerve (C6, C7) Origin Humeral head: medial epicondyle of humerus (via common flexor tendon) Ulnar head: - Olecranon process of ulna - Posterior border of ulna InserOon - Base of 5th metacarpal - Hook of hamate - Pisiform - Flexion of hand @ wrist - Flexion of forearm (weak) - AdducOon (ulnar deviaOon) of hand - Ulnar nerve (C7, C8) Picture Intermediate Layer: only one muscle FLEXOR DIGITORUM SUPERFICIALIS (FDS) = a split of two to allow FDP to pass through *Digitorum = digits 2-5* *IrritaOon of tendon sheath in CT + pressing the median nerve* Deep Layer FLEXOR DIGITORUM PROFUNDUS (FDP) *Dual innervaOon* *Role of medial + lateral halves of muscle in flexing the fingers – out of the 4 tendons of this muscle, the medial 2 tendons act on fingers 4 and 5 = ulnar nerve AND the lateral act on fingers 2 and 3 = median nerve* If paOent’s ulnar nerve is damaged, half of this muscle is paralyzed (medial half), thus flexion of fingers 4 or 5 become compromised, not 2 and 3 FLEXOR POLLICIS LONGUS (FPL) *One of the carpal tunnel muscles* Origin Humero-ulnar head: - Medial epicondyle of humerus (via common flexor tendon) - Coronoid process of ulna Radial head: - Proximal of anterior border of radius InserOon middle - Base of phalanges of fingers 25 - Flexion of fingers 2-5 @ MCP (metacarpophalangeal) and PIP joints (proximal interphalangeal) - Flexion of hand @ wrist joint - Flexion of forearm (weak) - Median Nerve (C7, C8, T1) Origin - Proximal anterior + medial surface of ulna - Interosseous membrane InserOon - Base of distal phalanges of fingers #2-5 - Flexion of fingers 2-5 @ MCP and PIP joints - Flexion of hand @ wrist joint (passes through wrist) - Median Nerve (C8, T1), radial ½ of muscle - Ulnar (C8, T1), ulnar ½ of muscle Origin Anterior surface of: radius + interosseous membrane InserOon - Base of distal phalanx of thumb - Flexion of thumb @ CMC (carpometacarpal), MCP (metacarpophalangeal) and IP (interphalangeal) joints - Median nerve (C7, C8) PRONATOR QUADRATUS (PQ) Origin Anterior surface of distal ¼ of ulna InserOon Anterior surface of distal ¼ of radius - PronaOon of forearm = radius crosses ulna thus radius moves (inserOon moves to origin) - Median nerve (C7, C8)