Upper Extremity Anatomy: Muscles, Bones, Nerves, and Clinical Correlates

Comprehensive vocabulary flashcards covering the muscular, osseous, articular, neural, and clinical anatomy of the upper extremity, including origins, insertions, innervations, actions, and pathological conditions.

Pronator teres

An anterior forearm muscle that originates at the medial epicondyle and inserts on the lateral surface of the radial bone midshaft. Innervated by the median nerve; acts to pronate the arm (radius flips over ulna). Typically shredded with an oblique presentation in lab.

Flexor carpi radialis

An anterior forearm muscle originating at the medial epicondyle and inserting on the carpal bones on the radial side. Innervated by the median nerve; acts to flex the radial side of the wrist and produce radial deviation.

Palmaris longus

A long, thin muscle of the anterior forearm originating at the medial epicondyle and inserting into the palmar aponeurosis. Innervated by the median nerve.

Flexor carpi ulnaris

An anterior forearm muscle originating at the medial epicondyle and inserting on the carpal bones on the ulnar side. Innervated by the ulnar nerve; acts in wrist flexion and ulnar deviation.

Flexor digitorum superficialis

An intermediate anterior forearm muscle originating at the medial epicondyle and inserting on the middle phalanx of digits 2-5. Innervated by the median nerve; flexes the wrist, MCP, and PIP joints of digits 2-5. Tendons pass through the carpal tunnel and split at the middle phalanx (Camper chiasm) to allow FDP tendons to pass through.

Flexor digitorum profundus

A deep anterior forearm muscle originating on the interosseous membrane and inserting on the distal phalanx of digits 2-5. Dual innervation: lateral half by median nerve, medial half by ulnar nerve. Flexes wrist, MCP, PIP, and DIP joints of digits 2-5. Gives origin to the lumbricals.

Camper chiasm

The structural bifurcation of the flexor digitorum superficialis (FDS) tendon over the middle phalanx that allows the flexor digitorum profundus (FDP) tendon to pass through deep to it toward the distal phalanx.

Pronator quadratus

A deep forearm muscle with horizontal striations situated directly on bone, originating on the anterior distal ulna and inserting on the anterior distal radius. Innervated by the median nerve; pronates the arm.

Flexor pollicis longus

A deep anterior forearm muscle originating on the anterior surface of the radius and interosseous membrane, inserting on the distal phalanx of the thumb. Innervated by the median nerve; flexes the IP joint of the thumb. Tendon travels through the carpal tunnel between the thenar muscles and adductor pollicis.

Thumb movements

Specialized movements of the first digit including adduction, palmar abduction, radial abduction, flexion, extension, and opposition across the carpometacarpal and metacarpophalangeal joints.

Abductor pollicis brevis

The most lateral muscle of the thenar eminence, originating from the flexor retinaculum, scaphoid, and trapezium, and inserting on the proximal phalanx of the thumb. Innervated by the recurrent branch of the median nerve; abducts the thumb away from the other fingers.

Flexor pollicis brevis

A thenar muscle originating from the flexor retinaculum, capitate, and trapezium, inserting onto the proximal phalanx of the thumb. Innervated by the recurrent branch of the median nerve; flexes the thumb toward the palm.

Opponens pollicis

A deep thenar muscle located between the APB and FPB, originating on the trapezium and inserting on the lateral side of the first metacarpal. Innervated by the recurrent branch of the median nerve; responsible for opposition of the thumb to the pinky.

Abductor digiti minimi

The most medial hypothenar muscle; innervated by the deep branch of the ulnar nerve; acts to abduct the pinky finger.

Flexor digiti minimi

The most lateral hypothenar muscle, originating on the hamate and inserting on the proximal phalanx of the pinky. Innervated by the deep branch of the ulnar nerve; acts to flex the pinky.

Opponens digiti minimi

A deep hypothenar muscle originating from the hamate and flexor retinaculum, inserting onto the fifth metacarpal. Innervated by the deep branch of the ulnar nerve; aids in pinky opposition to the thumb.

Palmar interossei (PAD)

Deep intrinsic hand muscles originating from the palmar surfaces of metacarpals 2, 4, and 5, inserting into the extensor hood and base of proximal phalanges 2, 4, and 5. Innervated by the deep branch of the ulnar nerve; adducts digits 2, 4, and 5.

Dorsal interossei (DAB)

Deep intrinsic hand muscles originating from adjacent sides of two metacarpal bones to act on digits 2-5. Innervated by the deep branch of the ulnar nerve; abducts digits 2-5.

Lumbricals

Intrinsic hand muscles originating from the tendons of the flexor digitorum profundus and inserting into the extensor hood. Lateral 2 innervated by the digital branches of the median nerve, medial 2 by the deep branch of the ulnar nerve. Action: flex MCP joints and extend PIP and DIP joints of digits 2-5.

Adductor pollicis

An intrinsic hand muscle originating from the capitate, bases of metacarpals 2 and 3, and the shaft of the 3rd metacarpal, inserting onto the base of the proximal phalanx of the thumb. Innervated by the deep branch of the ulnar nerve; adducts the thumb toward the other fingers.

Brachioradialis

Forearm muscle originating on the distal part of the humerus and inserting onto the styloid process of the radius. Spans the entire length of the forearm along the far lateral side; innervated by the radial nerve. Flexes the forearm in mid-pronation (hammer grip) with no action on the wrist.

Anconeus

A small muscle at the posterior elbow innervated by the radial nerve that supports and stabilizes the elbow joint.

Extensor carpi radialis longus

A superficial posterior forearm muscle originating on the lateral supracondylar ridge of the humerus and inserting in the carpal region. Innervated by the radial nerve; produces radial deviation and extension of the wrist.

Extensor carpi radialis brevis

A posterior forearm muscle with a thicker, shorter muscle belly than ECRL, originating on the lateral epicondyle. Innervated by the deep radial nerve; produces radial deviation and extension of the wrist.

Extensor digitorum

A wide but skinny superficial posterior forearm muscle originating at the lateral epicondyle and inserting into the extensor hood. Innervated by the posterior interosseous nerve (PIN); extends the digits.

Extensor digiti minimi

A superficial posterior forearm muscle originating at the lateral epicondyle and inserting onto the distal phalanx of digit 5, lying medial/ulnar to the extensor digitorum tendon to the pinky. Innervated by the posterior interosseous nerve (PIN).

Extensor carpi ulnaris

A medial posterior forearm muscle originating at the lateral epicondyle and inserting on the wrist/carpal bones (not digits). Innervated by the posterior interosseous nerve (PIN); extends and adducts the wrist.

Abductor pollicis longus

A deep outcropping muscle originating from the posterior surface of the radius just inferior to the anconeus insertion and inserting onto the base of the 1st metacarpal bone. Innervated by the PIN; forms the lateral border of the anatomical snuffbox.

Extensor pollicis longus

A deep posterior forearm muscle innervated by the PIN that extends the distal phalanx of the thumb at the IP, MCP, and CMC joints. Uses Lister's tubercle on the radius as a pulley and forms the medial border of the anatomical snuffbox.

Extensor pollicis brevis

A deep posterior forearm muscle innervated by the posterior interosseous nerve (PIN) that runs along the lateral border of the anatomical snuffbox alongside abductor pollicis longus.

Extensor indicis

A deep posterior forearm muscle innervated by the posterior interosseous nerve (PIN) whose tendon runs medial to the extensor digitorum tendon of the index finger.

Supinator

A deep muscle with oblique striations wrapped around the proximal radius, pierced by the deep radial nerve. Innervated by the deep radial nerve; acts to supinate the forearm.

Scalenes (Anterior and Middle)

Neck muscles serving as the origin landmark where the roots of the brachial plexus emerge (anterior scalene lies anterior to roots, middle scalene lies posterior to roots).

Triceps brachii

A three-headed posterior arm muscle: long head originates from the infraglenoid tuberosity, while all heads insert on the olecranon process of the ulna. Innervated by the radial nerve; extends the elbow and shoulder.

Coracobrachialis

A small, superior muscle originating on the coracoid process of the scapula and inserting on the humerus. Pierced by the musculocutaneous nerve; acts in shoulder flexion and adduction.

Biceps brachii

Anterior arm muscle with two heads: long head originates at the supraglenoid tuberosity (travels through the intertubercular groove) and short head originates at the coracoid process, both inserting on the radial tuberosity of the radius. Innervated by the musculocutaneous nerve; causes forearm supination, elbow flexion, shoulder flexion, and adduction.

Brachialis

A powerful anterior arm muscle situated directly on the shaft of the humerus, inserting onto the ulnar tuberosity. Innervated by the musculocutaneous nerve; serves as the primary agonist for elbow flexion.

Radius and Ulna Anatomy

The skeletal framework of the forearm featuring landmarks including the radial head, neck, radial tuberosity, styloid processes, olecranon, trochlear notch, coronoid process, and interosseous borders.

Scaphoid

A carpal bone located on the radial side that forms the floor of the anatomical snuffbox.

Pisiform

A small, sesamoid carpal bone located on the palmar and ulnar aspect of the wrist.

Hamate

A carpal bone characterized by the hook of hamate, which serves as a proximal attachment point for hypothenar muscles.

Trapezoid

The smallest carpal bone of the distal carpal row.

Trapezium

A distal carpal bone situated adjacent to the thumb metacarpal, articulating to form the first carpometacarpal joint.

Lister's tubercle

A dorsal bony projection on the distal radius near the radial styloid that acts as a pulley for the tendon of the extensor pollicis longus; serves as a landmark to determine posterior from anterior on the radius.

Radial tuberosity

A prominence on the medial aspect of the proximal radius that serves as the insertion site for the biceps brachii tendon.

Trochlear notch

A large C-shaped depression on the proximal ulna, formed by the coronoid process anteriorly and the olecranon process posteriorly, that articulates with the trochlea of the humerus.

Ulnar tuberosity

A roughened prominence on the proximal ulna inferior to the coronoid process that serves as the insertion site for the brachialis muscle.

Distal Humerus Features

Bony landmarks of the distal arm including the capitulum, trochlea, coronoid fossa, radial fossa, olecranon fossa, medial/lateral epicondyles, and the ulnar nerve groove.

Medial epicondyle of humerus

The large medial projection on the distal humerus serving as the common proximal origin for forearm flexor muscles; site of inflammation in golfer's elbow.

Lateral epicondyle of humerus

The lateral projection on the distal humerus serving as the common proximal origin for forearm extensor muscles; site of inflammation in tennis elbow.

Ulnar groove

A groove located on the posterior/medial aspect of the distal humerus behind the medial epicondyle that transmits the ulnar nerve toward the cubital tunnel ('funny bone' area).

Proximal Humerus Anatomy

Bony landmarks comprising the head of the humerus, anatomical neck, surgical neck, greater tubercle, lesser tubercle, intertubercular sulcus, and deltoid tuberosity.

Surgical neck of humerus

The constricted region of the humerus distal to the tubercles around which the axillary nerve and posterior circumflex humeral artery travel; common fracture site.

Greater tubercle of humerus

A lateral prominence on the proximal humerus that serves as the insertion site for the supraspinatus, infraspinatus, and teres minor; can impinge the subacromial space if not externally rotated during shoulder abduction.

Radial groove

A slanted groove along the posterior humeral shaft through which the radial nerve and profunda brachii artery wrap from posterior to anterior.

Annular ligament

A ligament that encircles the head of the radius horizontally, holding it against the radial notch of the ulna to form the proximal radioulnar joint.

Extensor retinaculum

A fibrous band passing over the posterior wrist from the radius to the ulnar styloid to prevent tendon bowstringing; divided into 6 distinct osteofibrous compartments.

Transverse carpal ligament

The thick, deep distal portion of the flexor retinaculum that spans the carpal arch to roof the carpal tunnel, containing the median nerve and nine flexor tendons.

Extensor hood

A complex dorsal aponeurosis over digits 2-5 into which extensor digitorum, lumbricals, and interossei insert, dividing into a central slip to the middle phalanx (PIP extension) and lateral bands to the distal phalanx (DIP extension).

Scaphoid fracture

Fracture of the scaphoid carpal bone, typically presenting with pain in the anatomical snuffbox, potentially endangering the radial artery and leading to avascular necrosis.

Mallet finger

A deformity resulting from the rupture of the terminal extensor digitorum tendon at its insertion on the distal phalanx, leading to an inability to actively extend the DIP joint.

Boxer's fracture

A fracture of the head/neck of the 5th metacarpal resulting from blunt trauma or punching hard surfaces, leading to the loss of the normal prominence of the pinky knuckle.

Boutonnière deformity

A digital deformity characterized by rupture of the central slip of the extensor tendon over the PIP joint, resulting in PIP joint flexion and secondary DIP hyperextension.

Trigger finger

Stenosing tenosynovitis characterized by chronic inflammation between the flexor tendons and sheath leading to tendon nodule formation and narrowing of the A1 pulley at the MCP joint, impairing smooth tendon gliding.

Elbow dislocation

Complete loss of articulation between the distal humerus and proximal radius/ulna involving disruption of the annular, radial collateral, and ulnar collateral ligaments, often resulting in posterior displacement following a FOOSH.

Nursemaid's elbow

Subluxation (partial dislocation) of the radial head slipping posteriorly out of the annular ligament, frequently seen in young children after sudden traction on an extended, pronated arm.

Guyon's canal compression

Distal entrapment of the ulnar nerve near the wrist, impacting intrinsic hand muscles and cutaneous distribution of the superficial branch while sparing the flexor carpi ulnaris.

Cubital tunnel syndrome

Proximal compression of the ulnar nerve near the elbow (behind the medial epicondyle), causing numbness/tingling in digit 5 and the medial half of digit 4, along with weakness in FCU, medial FDP, hypothenar muscles, lumbricals 3-4, and interossei.

Flexor zones of the hand

The five distinct anatomical zones (Zones I-V and TI-TIII) dividing the flexor tendon sheath pathways along the palm and digits, used to classify tendon injuries and repair prognosis.

Flexor zone 2 (No Man's Land)

The region spanning from the distal palmar crease to the middle phalanx containing both FDS and FDP tendons within a tight fibro-osseous tunnel, where tendon repairs historically carried a high risk of scarring and poor functional recovery.

Lateral epicondylitis (Tennis elbow)

Inflammation of extensor tendon origins at the lateral epicondyle caused by repetitive wrist extension and irritation of extensor carpi radialis brevis, aggravated by gripping motions.

Medial epicondylitis (Golfer's elbow)

Inflammation of flexor-pronator tendon origins at the medial epicondyle (e.g., FCU and FCR) resulting from repetitive wrist flexion and gripping motions.

Musculocutaneous nerve

Nerve arising from roots C5, C6, and C7 that pierces the coracobrachialis muscle to supply the anterior compartment of the arm (coracobrachialis, biceps brachii, brachialis) and terminates as the lateral antebrachial cutaneous nerve (LABC).

Radial nerve

Nerve arising from roots C5-T1 passing through the radial groove to innervate the triceps brachii, anconeus, brachioradialis, and ECRL, before dividing into superficial sensory and deep motor (PIN) branches.

Posterior interosseous nerve (PIN)

The continuation of the deep branch of the radial nerve after passing through the supinator muscle, supplying the deep and superficial extensor muscles of the forearm (ED, ECU, APL, EPL, EPB, EI, EDM).

Palmar cutaneous branch of median nerve

A sensory branch of the median nerve arising proximal to the wrist that does not pass through the carpal tunnel, providing cutaneous innervation to the central palm and thenar eminence.

Recurrent branch of median nerve

A motor branch of the median nerve passing through or just distal to the carpal tunnel to innervate the thenar eminence muscles (Abductor pollicis brevis, Flexor pollicis brevis superficial head, Opponens pollicis).

Upper extremity dermatomes (C5-T1)

Specific cutaneous sensory testing sites corresponding to spinal nerve roots: C5 at the lateral deltoid area, C6 at the tip of the thumb, C7 at the tip of the middle/index finger, C8 at the tip of the pinky, and T1 along the medial forearm.