Muscles of the Upper Extremity

Muscles of the Upper Extremity

• M. Pectoralis Minor

• Originates from ribs II-V, near the bone-cartilage margin.

• Inserts at the tip of the coracoid process.

• Depresses the shoulder girdle.

• Elevates the upper ribs, aiding in auxiliary breathing during inspiration.

• M. Pectoralis Major

• Clavicular part originates from the sternal half of the clavicle.

• Sternocostal part originates from the manubrium and body of the sternum, as well as the costal cartilage of ribs II-VII.

• Abdominal part originates from the anterior lamina of the rectus sheath.

• Inserts at the crest of the greater tubercle of the humerus.

• Responsible for shoulder joint adduction and inward rotation, most important for adduction.

• The clavicular part is responsible for anteversion, crucial for anteversion whereas it promotes retroversion from an anteverted position.

• M. Subclavius

• Originates from the bone-cartilage margin of rib I.

• Inserts on the lateral third of the clavicle.

• Stabilizes the sternoclavicular joint.

• Protects the subclavian vessels.

• The fascia of the subclavius and adventitia of the subclavian vein tightly adhere, maintaining the venous lumen open.

• M. Serratus Anterior

• Superior part originates from ribs I and II.

• Diverging part originates from ribs II and III.

• Converging part originates from ribs IV through IX.

• The superior part inserts at the superior angle of the scapula.

• The diverging part inserts at the medial border of the scapula.

• The converging part inserts at the inferior angle of the scapula.

• Holds the scapula against the trunk.

• Together with the rhomboids presses the scapula against the thorax.

• The superior part elevates the scapula and the diverging part depresses the scapula.

• The converging part depresses the scapula and rotates its lower angle for arm elevation over the horizontal axis.

• Each elevates ribs during inspiration when the scapula is fixed.

• M. Deltoideus

• The clavicular part originates from the acromial third of the clavicle.

• The acromial part originates from the acromion.

• The spinal part originates from the spine of the scapula.

• Inserts at the deltoid tuberosity.

• The clavicular part causes adduction (from approximately 60°), increasingly abduction, medial rotation, and anteversion.

• The acromial part causes abduction to the horizontal plane.

• The spinal part causes adduction (from approximately 60°), increasingly abduction, lateral rotation, and retroversion.

• M. Supraspinatus

• Originates from the supraspinous fossa and supraspinous fascia.

• Inserts at the upper facet of the greater tubercle, joint capsule.

• Abducts the shoulder joint at the scapular level.

• Also responsible for external rotation.

• M. Trapezius

• The descending part originates at the occipital bone between the highest and superior nuchal lines and the spinous processes of the upper cervical vertebrae.

• The transverse part originates from the spinous processes of the lower cervical and upper thoracic vertebrae.

• The ascending part originates from the spinous processes of the middle and lower thoracic vertebrae.

• The descending part inserts at the acromial third of the clavicle.

• The transverse part inserts at the acromion.

• The ascending part inserts at the spine of the scapula.

• The descending part prevents lowering of the shoulder girdle and arm.

• Elevates the scapula and rotates its lower tip laterally for arm elevation above the horizontal plane.

• Rotates the head when the shoulder is fixed and erects the cervical part of the vertebral column when innervated bilaterally.

• The transverse part pulls the scapula downwards.

• The ascending part depresses and rotates the scapula downwards.

• Elevates the scapula.

• M. Levator Scapulae

• Originates from the posterior tubercles of the transverse processes of the 1st-4th cervical vertebrae.

• Inserts at the superior angle of the scapula.

• Elevates the shoulder girdle.

• M. Rhomboideus Minor

• Originates from the spinous process of the 6th and 7th cervical vertebrae.

• Inserts at the medial border of the scapula cranial to the spine of the scapula.

• Pulls the scapula medially and cranially and fixes the scapula to the torso along with the serratus anterior.

• M. Rhomboideus Major

• Originates from the spinous process of the upper four thoracic vertebrae.

• Inserts at the medial border of the scapula caudal to the spine of scapula.

• Pulls the scapula medially and cranially and fixes the scapula to the torso along with the serratus anterior.

• M. Infraspinatus

• Originates from the infraspinous fossa and infraspinous fascia.

• Inserts at the middle facet of the greater tubercle, joint capsule.

• Responsible for lateral rotation.

• M. Teres Minor

• Originates from the middle third of the lateral border.

• Inserts at the lower facet of the greater tubercle, joint capsule.

• Responsible for shoulder joint lateral rotation and adduction in the scapular plane.

• M. Teres Major

• Originates from the inferior angle.

• Inserts at the crest of the lesser tubercle medial to the latissimus dorsi.

• Responsible for medial rotation, adduction, retroversion.

• M. Subscapularis

• Originates from the subscapular fossa.

• Inserts at the lesser tubercle, joint capsule.

• Responsible for medial rotation.

• M. Latissimus Dorsi

• Originates from the spinous process of the six lower thoracic vertebrae, lumbar vertebrae, thoracolumbar fascia, dorsal surface of the sacrum, outer lip of iliac crest, and ribs IX–XII; frequently the inferior angle of the scapula.

• Inserts at the crest of the lesser tubercle.

• Action is adduction, medial rotation, and retroversion.

• M. Biceps Brachii

• The long head originates from the supraglenoid tubercle.

• The short head originates from the tip of the coracoid process.

• Inserts at the radial tuberosity via the bicipital aponeurosis at the antebrachial fascia.

• The long head causes abduction, anteversion, and medial rotation.

• The short head causes adduction, anteversion, and medial rotation in the shoulder joint.

• The elbow joint causes flexion with the most action and supination with a flexed elbow.

• M. Coracobrachialis

• Originates from the coracoid process.

• Inserts at the anterior surface of the humerus medial and distal to the crest of the lesser tubercle.

• Causes medial rotation, adduction, and anteversion of the shoulder joint.

• M. Brachialis

• Originates from the anterior surface of the humerus (lower half).

• Inserts at the tuberosity of ulna.

• Causes flexion of the elbow joint and tenses the joint capsule.

• M. Triceps Brachii -The long head originates from the infraglenoid tubercle.

• The medial head originates from the posterior surface of the humerus medial and distal of the radial groove.

• The lateral head originates from the posterior surface of the humerus lateral and proximal of the radial groove.

• Inserts at the olecranon.

• The long head causes adduction and retroversion of the shoulder joint.

• The elbow joint causes extension.

• M. Pronator Teres

• The humeral head originates from the medial epicondyle of the humerus.

• The ulnar head originates from the coronoid process.

• Inserts at the middle third of the lateral surface of the radius.

• Causes pronation (most important muscle) and flexion of the elbow joint.

• M. Flexor Carpi Radialis

• Originates from the medial epicondyle of the humerus and the antebrachial fascia.

• Inserts to the palmar area of the base of metacarpal II.

• Causes flexion and pronation of the elbow joint.

• Also causes palmar flexion and radial abduction of the carpal joint.

• M. Flexor Carpi Ulnaris

• The humeral head originates from the medial epicondyle of the humerus.

• The ulnar head originates from the olecranon and upper two-thirds of the posterior border of the ulna.

• Inserts via the pisiform and the pisometacarpal and pisohamate ligaments at the base of metacarpal V and the hamate.

• Causes flexion of the elbow joint.

• Also causes palmar flexion and ulnar abduction of the carpal joint.

• M. Brachioradialis

• Originates from the lateral border of the humerus.

• Inserts at the proximal of the styloid process of the radius.

• Causes flexion of the elbow joint (most effective from a mid-flexed position)

• Facilitates pronation or supination from opposite end-of-range positions.

• M. Extensor Carpi Radialis Longus

• Originates from the lateral supracondylar ridge up to the lateral epicondyle.

• Inserts at the dorsal area of the base of metacarpal II.

• Causes flexion and pronation of the elbow joint.

• Also causes dorsiflexion and radial abduction of the carpal joint.

• M. Extensor Carpi Radialis Brevis

• Originates from the lateral epicondyle of the humerus.

• Inserts at the dorsal area of the base of metacarpal III.

• Causes flexion and pronation of the elbow joint.

• Also causes dorsiflexion and radial abduction of the carpal joint.

• M. Extensor Carpi Ulnaris

• Originates from the humeral head which is at the lateral epicondyle of the humerus.

• Originates from the ulnar head which is at olecranon, posterior surface of the ulna, antebrachial fascia

• Inserts at the dorsal area of metacarpal V

• Causes extension on the elbow joint

• Dorsiflexion, ulnar abduction on the carpal joint

• M. Extensor Digitorum

• Originates from lateral epicondyle of the humerus, antebrachial fascia

• Inserts at dorsal aponeuroses of the 2nd-5th fingers

• Causes elbow joint extension

• Dorsiflexion on the carpal joint

• Extension on metacarpophalangeal joints (II–V)/ interphalangeal joints (II–V) is the most important extensor in the metacarpophalangeal and proximal interphalangeal joints

• M. Supinator

• Originates from lateral epicondyle of humerus, supinator crest of the ulna, radial collateral and anular ligaments of radius

• Inserts at anterior surface of the radius (proximal third)

• Causes supination on the radio-ulnar joints - most important muscle with extended elbow

• M. Flexor Digitorum Superficialis

• Originates from humero-ulnar head: medial epicondyle of the humerus, coronoid process.

• Originates from radial head: anterior surface of the radius

• Inserts with four long tendons at the base of the middle phalanx of the 2nd-5th fingers

• Elbow flexion on teh elbow joint

• Palmar flexion on the carpal joint

• Flexion on the metacarpophalangeal joints (II–V)

• Flexion on the proximal interphalangeal joints (II–V) is the most important flexor of this muscle

• M. Flexor Digitorum Profondus

• Originates from anterior surface of the ulna, interosseous membrane

• Inserts at base of the distal phalanx of the 2nd-5th fingers

• Palmar Flexion in the carpal joint

• Flexion of the metacarpophalangeal joints (II–V)

• Flexion on the interphalangeal joints is the most important flexor