Upper Limb Anatomy: Muscles, Attachments, Actions, and Innervation

Comprehensive vocabulary flashcards detailing the anatomical attachments, actions, and nervous innervation of the muscles of the pectoral region, shoulder, arm, forearm, and hand.

Pectoralis major

A large chest muscle originating in three parts (clavicular head, sternocostal head from the sternum and costal cartilages 1 to 4, and abdominal part) and inserting into the intertubercular sulcus; it adducts and medially rotates the arm and is innervated by the lateral and medial pectoral nerves.

Pectoralis minor

A chest muscle situated deep to pectoralis major that attaches to the coracoid process of the scapula and the outer surfaces of ribs 3 to 5; it depresses the scapula, fixes the clavicle, acts as an accessory muscle of respiration, and is innervated by the lateral and medial pectoral nerves.

Subclavius

A small muscle filling the space between the first rib and the inferior surface of the clavicle at the groove for the subclavius muscle; it is innervated by the subclavian nerve from the brachial plexus.

Serratus anterior

A muscle attached between the medial border of the scapula and ribs 1 through 9 that protracts and rotates the scapula (used in boxing) and assists in arm abduction; it is innervated by the long thoracic nerve.

Deltoid

A shoulder muscle with three proximal attachments (clavicular part from the lateral third of the clavicle, acromial part, and spinal part) that inserts into the deltoid tuberosity on the anterolateral humerus; it abducts the arm up to the horizontal position ($90^\circ$) and is innervated by the axillary nerve.

Rotator cuff muscles

A group of four muscles—subscapularis, supraspinatus, infraspinatus, and teres minor—that provide active stabilization of the shoulder joint to prevent dislocations.

Subscapularis

A rotator cuff muscle filling the subscapular fossa on the costal/anterior surface of the scapula and inserting into the lesser tubercle of the humerus; it functions as an internal rotator and adductor of the arm and is innervated by the subscapular nerve.

Supraspinatus

A rotator cuff muscle located in the supraspinous fossa that inserts into the greater tubercle of the humerus; it abducts the arm and is innervated by the suprascapular nerve.

Infraspinatus

A rotator cuff muscle occupying the infraspinous fossa that inserts into the greater tubercle of the humerus; it provides lateral rotation and abduction of the arm and is innervated by the suprascapular nerve.

Teres minor

A cylindrical rotator cuff muscle attaching to the lateral border of the scapula and the greater tubercle of the humerus; it produces lateral rotation and is innervated by the axillary nerve.

Teres major

A muscle originating from the inferior angle of the scapula and passing anteriorly to insert into the medial lip of the intertubercular sulcus of the humerus; it provides medial rotation and adduction and does not belong to the rotator cuff.

Biceps brachii

A two-headed muscle in the anterior compartment of the arm; the long head originates from the supraglenoid tubercle, and the short head originates from the coracoid process of the scapula, both inserting onto the radial tuberosity to flex the elbow; innervated by the musculocutaneous nerve.

Coracobrachialis

A deep anterior arm muscle originating from the coracoid process of the scapula and inserting onto the middle third of the anteromedial surface of the humerus; it flexes the upper arm and is pierced by the musculocutaneous nerve.

Brachialis

Anterior arm muscle arising from the distal half of the anterolateral and anteromedial surfaces of the humerus and inserting into the ulnar tuberosity; it flexes the forearm and is innervated by the musculocutaneous nerve.

Triceps brachii

The extensor muscle of the posterior compartment of the arm comprising three heads (long head from the infraglenoid tubercle, lateral head above the radial groove, and medial head below the radial groove) inserting onto the olecranon of the ulna; innervated by the radial nerve.

Medial epicondyle of the humerus

The bony landmark of the distal humerus that serves as the common origin for the superficial muscles of the anterior compartment of the forearm.

Pronator teres

A superficial anterior forearm muscle originating via a humeral head (medial epicondyle) and an ulnar head (coronoid process) and inserting into the pronator tuberosity on the lateral surface of the radius; it pronates the forearm and is innervated by the median nerve.

Flexor carpi radialis

A superficial anterior forearm muscle originating from the medial epicondyle and inserting on the base of the second metacarpal bone; it produces flexion and abduction of the hand and is innervated by the median nerve.

Palmaris longus

A superficial anterior forearm muscle absent in approximately 10% of the population; it arises from the medial epicondyle and inserts into the palmar aponeurosis to tense it, innervated by the median nerve.

Flexor carpi ulnaris

A superficial anterior forearm muscle originating from the medial epicondyle and inserting into the pisiform bone; it produces flexion and adduction of the hand and is uniquely innervated by the ulnar nerve.

Flexor digitorum superficialis

A superficial anterior forearm muscle with humeroulnar and radial heads that splits into four tendons inserting onto the middle phalanges of digits 2 through 5; it flexes the middle phalanges and is innervated by the median nerve.

Flexor digitorum profundus

A deep anterior forearm muscle originating from the ulna and interosseous membrane, inserting via four tendons into the distal phalanges of digits 2 through 5; it flexes the distal phalanges and has dual innervation (medial/ulnar half by the ulnar nerve, lateral half by the median nerve).

Flexor pollicis longus

A deep anterior forearm muscle arising from the anterior surface of the radius and interosseous membrane and inserting into the distal phalanx of the thumb; it flexes the thumb and is innervated by the median nerve.

Pronator quadratus

A quadrilateral deep muscle situated across the distal anterior surfaces of the radius and ulna that produces pronation of the forearm; innervated by the median nerve.

Brachioradialis

A muscle belonging to the posterior compartment that originates from the lateral supracondylar ridge and inserts onto the styloid process of the radius; it is an exception in its compartment because it flexes the forearm, though it is innervated by the radial nerve.

Extensor carpi radialis longus

A superficial posterior forearm muscle originating from the lateral supracondylar ridge and inserting onto the base of the second metacarpal bone; it extends the hand and is innervated by the radial nerve.

Extensor carpi radialis brevis

A superficial posterior forearm muscle originating from the lateral epicondyle of the humerus and inserting onto the base of the third metacarpal bone; it extends the hand and is innervated by the radial nerve.

Extensor digitorum

A superficial posterior forearm muscle originating from the lateral epicondyle and dividing into four tendons that insert on both the middle and distal phalanges of digits 2 through 5; it extends the fingers and is innervated by the radial nerve.

Anconeus

A small triangular muscle located on the posterior aspect of the olecranon originating from the lateral epicondyle of the humerus; innervated by the radial nerve.

Supinator

A deep posterior forearm muscle originating from the lateral epicondyle that spirals around to attach to the lateral surface of the radius; it supinates the forearm and is innervated by the radial nerve.

Abductor pollicis longus

A deep posterior forearm muscle originating from the posterior surfaces of the radius, ulna, and interosseous membrane, inserting onto the base of the first metacarpal bone; it abducts the thumb and is innervated by the radial nerve.

Extensor pollicis brevis

A deep posterior forearm muscle arising from the posterior surface of the radius and interosseous membrane, inserting onto the proximal phalanx of the thumb; it extends the thumb and is innervated by the radial nerve.

Extensor pollicis longus

A deep posterior forearm muscle arising from the posterior surface of the ulna and interosseous membrane, inserting onto the distal phalanx of the thumb; it extends the thumb and is innervated by the radial nerve.

Extensor indicis

A deep posterior forearm muscle originating from the posterior surface of the ulna and interosseous membrane that inserts into the second (index) digit to provide extension; innervated by the radial nerve.

Thenar muscles

The group of short intrinsic hand muscles forming the muscular elevation at the base of the thumb, consisting of abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and adductor pollicis.

Opponens pollicis

A deep thenar muscle that enables opposition, allowing the tip of the thumb to touch the tips of the other fingers.

Hypothenar muscles

The group of intrinsic hand muscles forming the elevation at the base of the fifth digit, consisting of abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi; all are innervated by the ulnar nerve.

Lumbrical muscles

Four intrinsic hand muscles numbered 1 to 4 from lateral to medial that flex the metacarpophalangeal joints and extend the interphalangeal joints; the first two are innervated by the median nerve, and the third and fourth by the ulnar nerve.

Palmar interosseous muscles

Three intrinsic hand muscles occupying the palmar aspect of the interosseous spaces between metacarpals; they act as adductors of the digits and are innervated by the ulnar nerve.

Dorsal interosseous muscles

Four intrinsic hand muscles situated on the dorsal aspect of the interosseous spaces; they act as abductors of the digits and are innervated by the ulnar nerve.