Arm Muscles

Muscle Group Muscle Innervation Function Pathology Shoulder Girdle Muscles (Posterior) Deltoid Axillary N. C5-C6 Main abductor of arm up to 90 degrees Anterior/ clavicle part: adducts, flexes, and medially rotates arm Middle/ acrominal part: abduct arms, aids clavicle part in anteversion Posterior/ spinal part: retroversion (extension) of arm and lateral rotation of arm Axillary N. injury: usually caused by fracture of surgical neck of the humorous or dislocation of the shoulder. Patient could not abduct arm due to paralysis of deltoid. Supraspinatus Suprascapular N. C4-C6 Abductor of arm Rotator cuff muscle group Rotator cuff group: maintain stability of the shoulder joint Rotator cuff injury: tendinopathy of the supraspinatus (often in athletes) calcification, pain, tendon rupture, and avulsion of the greater tubercle ae among the various pathologies found in this group. Techniques and operative methods have been introducd since the first rotator cuff repair was reported by W. Muller in 1898 Infraspinatus Lateral rotator of arm Rotator cuff muscle group Teres Minor Axillary N. C5-C6 Teres Major Lower Subscapular N. C6-C7 Adduction and medial rotation of arm Latissimus Dorsi Thoracodorsal N. C6-C8 Medial rotation, extension, & adduction of arm Coughing and forced respiration Subscapularis Subscapular N. C5-C7 Adduction and medial rotation of the Arm Rotator cuff injury Paralysis causes maximal lateral rotation Shoulder Girdle Muscles (Anterior) Pectoralis Major Lateral and Medial Pectoral N. C5-T1 Adduction and medial rotation of the arm Lowers arm when raised Clavicle part: flexor of upper arm (anteversion) Assists in respiration by expanding thoracic cage during forced respiration Pectoralis Minor Medial Pectoral N. C8-T1 Pulls the scapula forward and downward Rotation of scapula so that glenoid cavity faces downward Attaches to coracoid process Coracobrachialis Musculocutaneous N. C5-C7 Aids flexion (anteversion) and adduction of arm Attaches to coracoid process Serratus Anterior Long Thoracic N. C5-C7 Elevation of arm over 90 degrees Protracts scapula (holds it against thoracic wall) Rotates scapula laterally to elevate arm Accessory muscle of respiration by lifting ribs Injury to the Long Thoracic N. = no elevation of the arm or winged scapula Winged Scapula: paralysis of serratus anterior or injury to long thoracic n. cause the scapula to protrude from the back Anterior Muscles of Arm Biceps Brachii Musculocutaneous N. Flexion/ anteroversion of shoulder joint Muscle is flexor and supinator (palm up) of forearm Long head: abductor & medial rotator of arm Short Head: Attaches to coracoid process Brachialis Power flexor of elbow joint Coracobrachialis Flexion (anteversion) and adduction of arm Posterior Muscles of Arm Triceps Brachii Radial N. Strong extensor of forearm Aids in adduction and retroversion of arm and shoulder joint Mediates extension at elbow joint Anconeus Assists triceps brachii in extension of elbow Superficial Anterior Muscles of the Forearm Palmaris Longus Median N. Flexes hand Tenses palmer aponeurosis (it attaches to it) Golfer’s Elbow: form of tendinitis; tendinous sheath of the anterior muscles of the forearm (which inserts into the medial epicondyle of the humerus at the medial side of the elbow joint) becomes inflamed. Causes painful bony bump on elbow and pain may radiate down forearm. Pronator Syndrome: Compression of the median nerve at the elbow Can cause pain and/or numbness in the distribution of the distal median nerve, and weakness of the muscles innervated by the anterior interosseous nerve Pronator Teres Pronation of forearm Flexion at elbow Flexor Carpi Radialis Palmar flexion Radial abduction of the hand Flexes and pronates the elbow Flexor Digitorum Superficialis Flexion of the elbow, the wrist, and the fingers (Medial N is found beneath) Flexor Carpi Ulnaris Ulnar N. Flexor and adductor of hand Paralyzed by Median and Ulnar N. Injury Deep Anterior Muscles of the Forearm Flexor Pollicis Longus Median N. Flexor of terminal phalanx (thumb) Flexor Digitorum Profundus Laterally: Median N. Medially: Ulnar N. Flexes midcarpal joints (wrist), metacarpophalange-al joint, and phalangeal joints Ulnar part: Paralyzed by Median and Ulnar N. Injury Pronator Quadratus Median N. Pronates forearm (with pronator teres) Posterior Muscles of Forearm (Radial Group Muscles) Brachioradialis Radial N. Pronation or supination of forearm Bring forearm BW supination and pronation Flexor at elbow joint (forearm flexor) Paralyzed in Radial N. Injury and cause wrist drop Extensor Carpi Radialis Longus Extension and radial abduction of hand at wrist joint Weak flexor of elbow Aids in pronation and supination of forearm Extensor Carpi Radialis Brevis Extensor and abductor of hand at wrist joint Weak flexor of elbow Tennis Elbow: form of tendinitis; outer part of elbow becomes sore and tender; tendon of extensor carpi radialis brevis becomes degenerated where it attaches to the lateral epicondyle?on the outside of the elbow (humorous). Causes pain when pressure is applied to the outside of the elbow and pain may radiate down forearm. Paralyzed in Radial N. Injury and cause wrist drop Superficial Posterior Muscles of Forearm Extensor Digitorum Posterior Interosseos Branch of the Deep Radial N. C7-C8 Extends 4 medial fingers (not thumb) Dorsiflexion of hand at wrist Paralyzed in Radial N. Injury and cause wrist drop Extensor Carpi Ulnaris Extends and adducts hand at wrist Extensor Digiti Minimi Extension of 5th digit and dorsiflexion of hand Paralyzed in Radial N. Injury and cause wrist drop Deep Posterior Muscles of Forearm Supinator Deep Branch of Radial N. C5-C6 Supinates forearm Abductor Pollicis Longus Posterior Interosseos Branch of the Deep Radial N. C7-C8 Abduction of the thumb Extension of thumb at carpometacarpal joint Extensor Pollicis Brevis Extension of proximal phalanx at the metacarpophalangeal joint Extensor Pollicis Longus Extends thumb at metacarpophalangeal and interphalangeal joints using the crest on radius as a fulcrum (the point on which a lever rests) Extensor Indicis Index extension Hand dorsiflexion BW Palmar Aponeurosis and Hypothenar Eminence Palmaris Brevis Ulnar N. Dupuytren’s contracture: progressive fibrosis; thickening and shortening of the palmer aponeurosis that leads to partial flexion of the ring and small finger Thenar Muscles Abductor Pollicis Brevis Median N Abduction of thumb Paralyzed by Median N. Injury Flexor Pollicis Brevis Superficial head: Median N. Deep head: Ulnar N. Flexion of thumb Opponens Pollicis Median N. Thumb opposition Adductor Pollicis Deep Branch of Ulnar N. Thumb adduction Not paralyzed by Median N. Injury – causes ape hand Hypothenar Muscles Adductor Digiti Minimi Adducts 5th digit Flexor Digiti Minimi Flexes 5th digit Opponens Digiti Minimi Opposition of the 5th finger to the thumb Muscles of the Metacarpus Lumbricals 2 Lateral Muscles: Median N. 2 Median Muscles: Ulnar N. 1st and 2nd lumbricals are paralyzed due to Median N. Injury 3rd and 4th lumbricals are paralyzed due to Ulnar N. Injury (results in claw hand) Palmer Interossei Muscles Ulnar N. Adduction of digits Assisting Lumbricals Paralyzed by Ulnar N. Injury Dorsal Interossei Muscles Abduction of digits