Flexor Region of the Forearm

Gross Anatomy


Flexor Region of the Forearm


Anatomy Tables for Today's Topic

Bones of the Flexor Forearm Region
Bones of the Wrist and Hand
Muscles of the Forearm Flexor Region
Nerves of the Forearm Flexor Region
Arteries of the Forearm Flexor Region
Joints - Radioulnar and Wrist
Fasciae of the Forearm Flexor Region

Bones of the Flexor Forearm Region

Bone Structure Description Notes
humerus   the bone of the arm (brachium) the humerus articulates proximally with the scapula at the glenoid fossa; it articulates distally with the radius and ulna at the elbow joint
lateral epicondyle a knob-like projection on the lateral side of the humerus proximal to the capitulum it is the site of attachment of the common extensor tendon which is the origin of several forearm extensor muscles (extensor carpi radialis brevis m., extensor digitorum m., extensor digiti minimi m. and extensor carpi ulnaris m.); inflammation of the attachment of the common extensor tendon is called lateral epicondylitis which is also known as "tennis elbow"
medial epicondyle a knob-like projection on the medial side of the humerus proximal to the trochlea it is the attachment site of the common flexor tendon which is the origin for the superficial group of forearm flexor muscles (pronator teres m., flexor carpi radialis m., palmaris longus m., flexor carpi ulnaris m. and flexor digitorum superficialis m.); inflammation of the attachment of the common flexor tendon is called medial epicondylitis; the ulnar nerve is in contact with bone as it courses posterior to the medial epicondyle where it is susceptible to injury from blunt trauma or fracture
medial supracondylar ridge a narrow ridge running proximally from the medial epicondyle of the humerus the pronator teres m. takes origin from the common flexor tendon near the most inferior part of the medial supracondylar ridge
lateral supracondylar ridge a narrow ridge running proximally from the lateral epicondyle of the humerus it is the site of origin of the brachioradialis m. and the extensor carpi radialis longus m.
coronoid fossa the depression on the anterior surface of the humerus located proximal to the trochlea near the elbow it accommodates the coronoid process of ulna when the elbow is flexed
radial fossa the depression on the anterior surface of the humerus located proximal to the capitulum near the elbow it accommodates the head of the radius when the elbow is flexed
olecranon fossa the depression on the posterior surface of the humerus located just proximal to the elbow it accommodates the olecranon process of the ulna when the elbow is extended
capitulum the rounded process that caps the distal end of the lateral condyle of the humerus it articulates with the head of the radius; capitulum means "little head"
trochlea the grooved process that caps the distal end of the medial condyle of the humerus it articulates with the trochlear notch of the ulna; the shape of the trochlea and the trochlear notch limits side-to-side movement and guarantees a hinge action; trochlea means "pulley"
ulna   the bone on the medial side of the forearm (antebrachium) the ulna articulates proximally with the trochlea of the humerus and the head of the radius; it articulates distally with the ulnar notch of the radius
olecranon the proximal end of the ulna it is the insertion site of the tendon of the triceps brachii m.; when the elbow is extended, the olecranon of the ulna engages the olecranon fossa of the humerus
trochlear notch the crescent shaped notch on the anterior surface of the proximal end of the ulna it is located between the olecranon and the coronoid process; it articulates with the trochlea of the humerus; a ridge within the trochlear notch fits into the groove in the trochlea of the humerus which limits side-to-side movement and guarantees a hinge action
coronoid process the anterior projection of bone located distal to the trochlear notch it is the insertion site of the brachialis m.
radial notch the notch on the lateral surface of the ulna located just distal to the trochlear notch it accommodates the head of the radius; the ends of the annular ligament attach to the anterior and posterior edges of the radial notch of the ulna to encircle the head of the radius
body the long slender midportion of the ulna it is also called the shaft or diaphysis; the interosseous membrane attaches to the entire length of the interosseous border of the body of the ulna
head the distal end of the ulna it is small and rounded for articulation with the radius
styloid process a small projection from the distal surface of the head of the ulna it is the site of attachment of the articular disk of the distal radioulnar joint
radius   the bone on the lateral side of the forearm (antebrachium) the radius pivots on its long axis and crosses the ulna during pronation
head the rounded proximal end of the radius it has a smooth, rounded surface for articulation with the ulna; the head of the radius is encircled by the annular ligament (4/5 of a circle) and the radial notch of the ulna (1/5 of a circle)
neck the constricted area of the radius located distal to the head the annular ligament of the radius surrounds the head of the radius, not the neck of the radius
radial tuberosity a roughened area on the anteromedial surface of the radius located just distal to the neck it is the insertion site of the tendon of the biceps brachii m.
body the long, slender midportion of the radius it is also known as the shaft or diaphysis; the interosseous membrane attaches to the entire length of the body of the radius along its interosseous border; a fracture of the distal end of the body of the radius with a dorsal displacement of the distal fragment is quite common and is called a Colles' fracture
ulnar notch a shallow notch located on the medial surface of the distal end of the radius it articulates with the head of the ulna
styloid process the distal-most projection from the lateral side of the radius the radial styloid process projects lateral to the proximal row of carpal bones

Bones of the Wrist and Hand

Bone Structure Description Notes
carpal bones   the bones of the wrist eight bones arranged in two rows; a pneumonic for memorizing the carpal bones is " some lovers try positions that they can't handle" - the first letters of these eight words are the first letters of the names of the eight carpal bones arranged from lateral to medial, proximal row first: scaphoid, lunate, triquitrum, pisiform/trapezium, trapezoid, capitate, hamate
proximal row lateral to medial: scaphoid, lunate, triquetrum, pisiform the scaphoid and lunate bones of the proximal row articulate with the distal end of the radius
distal row lateral to medial: trapezium, trapezoid, capitate, hamate the distal row of carpal bones articulates with the metacarpal bones of the hand
scaphoid   the most lateral carpal bone of the proximal row the scaphoid bone is located in the floor of the anatomical snuff box; it is frequently fractured by hyperextension and abduction of the wrist; scaphoid means "boat-shaped"
lunate   the carpal bone located between the scaphoid and triquetrum in the proximal row the lunate is so named because it is "moon-shaped" (crescent shaped) in longitudinal section; the head of the capitate sits within the crescent of the lunate
triquetrum   the carpal bone between the lunate and pisiform bones in the proximal row of carpal bones it articulates with the pisiform which sits anterior to it
pisiform   a sesamoid bone in the tendon of the flexor carpi ulnaris m. it articulates with the triquetrum; the pisiform bone provides a protective function for the flexor carpi ulnaris tendon by bearing the forces generated by the tendon riding across the triquitrum, especially during wrist extension; pisiform means "pea-shaped"
trapezium   the most lateral carpal bone of the distal row it forms a saddle joint with the metacarpal bone of the thumb; "the thumb swings on the trapezium"
trapezoid   the carpal bone located between the trapezium and the capitate in the distal row the trapezoid is named for its trapezoid shape
capitate   the carpal bone located between the trapezoid and the hamate in the distal carpal row the capitate is the largest carpal bone; it is named for its rounded head; forces generated in the hand (as during a punching blow with the fist) are transmitted through the third metacarpal bone to the capitate and proximally through the lunate to the radius
hamate   the most medial carpal bone in the distal row the hamulus (hook) of the hamate is its distinguishing characteristic; it is an attachment point of the flexor retinaculum
metacarpal bones   the bones located between the carpal bones (wrist) and the phalanges (fingers) of the hand there are a total of five metacarpal bones in the hand; the metacarpals of digits 2-5 are bound together by ligaments to form a firm foundation for finger movements; the metacarpal of the thumb is more independent in its range of motion
base the proximal end of the metacarpal it articulates with the distal row of carpal bones
body the slender shaft of the metacarpal it is also known as the diaphysis
head the rounded distal end of the metacarpal it articulates with the proximal phalanx of the corresponding digit
phalanx (phalanges)   the distal two or three bones in the digits of the hand there are a total of 14 phalanges in the hand; the thumb has two phalanges (proximal and distal) and each of the other digits has three phalanges (proximal, middle and distal); phalanx means "line of soldiers"
base the proximal end of the phalanx the base of the proximal phalanx articulates with the head of the corresponding metacarpal bone; the base of the middle or distal phalanx articulates with the head of the next proximal phalanx
body the slender shaft of the phalanx also known as the diaphysis; the body of the distal phalanx is very short
head the distal end of the phalanx the proximal, middle and distal phalanges each have a head; the head of a proximal or middle phalanx articulates with the base of the next distal phalanx

Muscles of the Forearm Flexor Region

Muscle Origin Insertion Action Innervation Artery Notes
flexor carpi radialis common flexor tendon from the medial epicondyle of the humerus base of the second and third metacarpals flexes the wrist, abducts the hand median nerve ulnar a. functions synergistically with the extensor carpi radialis longus and brevis mm. to abduct hand
flexor carpi ulnaris common flexor tendon & (ulnar head) from medial border of olecranon & upper 2/3 of the posterior border of the ulna pisiform, hook of hamate, and base of 5th metacarpal flexes wrist, adducts hand ulnar nerve ulnar a. the ulnar nerve passes between the two heads of origin of the flexor carpi ulnaris m.
flexor digitorum profundus posterior border of the ulna, proximal two-thirds of medial border of ulna, interosseous membrane base of the distal phalanx of digits 2-5 flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints median nerve (radial one-half); ulnar nerve (ulnar one-half) ulnar a., anterior interosseous a. ulnar nerve innervates the portion of profundus that acts on digits 4 & 5 (the ulnar 2 digits)
flexor digitorum superficialis humeroulnar head: common flexor tendon; radial head: middle 1/3 of radius shafts of the middle phalanges of digits 2-5 flexes the metacarpophalangeal and proximal interphalangeal joints median nerve ulnar a. median nerve travels distally in the forearm on the deep surface of the flexor digitorum superficialis m.
flexor pollicis longus anterior surface of radius and interosseous membrane base of the distal phalanx of the thumb flexes the metacarpophalangeal and interphalangeal joints of the thumb median nerve anterior interosseous a. the tendon of flexor pollicis longus passes through the carpal tunnel with the other long digital flexor tendons and the median nerve
palmaris longus common flexor tendon, from the medial epicondyle of the humerus palmar aponeurosis flexes the wrist median nerve ulnar a. palmaris longus is absent in about 13% of forearms; it may be present on one side only
pronator quadratus medial side of the anterior surface of the distal one-fourth of the ulna anterior surface of the distal one-fourth of the radius pronates the forearm median nerve via the anterior interosseous nerve anterior interosseous a. pronator quadratus is the deepest muscle in the distal forearm; it functions synergistically with pronator teres and has the same nerve supply
pronator teres common flexor tendon and (deep or ulnar head) from medial side of coronoid process of the ulna midpoint of the lateral side of the shaft of the radius pronates the forearm median nerve ulnar a., anterior ulnar recurrent a. median nerve passes between the two heads of origin of pronator teres

Nerves of the Forearm Flexor Region

Nerve Source Branches Motor Sensory Notes
anterior interosseous n. median n. no named branches flexor pollicis longus m., radial half of flexor digitorum profundus m., pronator quadratus m. none courses along the anterior surface of the interosseous membrane
deep radial n. radial n. posterior interosseous n. extensor carpi radialis brevis m., supinator m., extensor digitorum m., extensor digiti minimi m., abductor pollicis longus m., extensor pollicis longus m. extensor pollicis brevis m., extensor indicis m. no cutaneous branches deep radial n. passes through the supinator m.; some authors consider the posterior interosseous n. and the deep radial n. to be synonymous, others consider the deep radial n. to become the posterior interosseous n. when it emerges from the supinator m. in the posterior forearm
median n. lateral and medial cords of the brachial plexus unnamed muscular branches, anterior interosseous n., palmar br., recurrent (motor) br., common palmar digital nn. (for digits 1-3) pronator teres m., flexor carpi radialis m., palmaris longus m., flexor digitorum superficialis m., flexor digitorum profundus m. (radial half), flexor pollicis longus m., pronator quadratus m., abductor pollicis brevis m., flexor pollicis brevis m., opponens pollicis m., lateral 2 lumbrical mm. skin of the radial half of the palm and palmar side of the lateral 3 1/2 digits (and nail bed for these digits) the median n. is motor to the flexor muscles of the forearm (except flexor carpi ulnaris and the medial 1/2 of the flexor digitorum profundus),the muscles of the thenar compartment and the lateral 2 lumbricals
radial n. posterior cord of the brachial plexus unnamed muscular branches, posterior brachial cutaneous n., inferior lateral brachial cutaneous n., posterior antebrachial cutaneous n., superficial and deep brs. muscles of the posterior arm: triceps brachii m., anconeus m.; muscles of the posterior forearm: brachioradialis, extensor carpi ulnaris m., extensor carpi radialis longus m., extensor carpi radialis brevis m., extensor digitorum m., extensor digiti minimi m., supinator m., abductor pollicis longus m., extensor pollicis longus m., extensor pollicis brevis m., extensor indicis m. skin of the posterior arm, forearm and hand all of the muscles on the posterior side of the arm and forearm are innervated by the radial n.
superficial radial n. radial n. dorsal digital brs. sympathetic motor for the skin skin of the posterolateral wrist and hand; dorsum of the lateral 3 1/2 digits (excluding the skin over the distal phalanx/nail bed) superficial radial n. is located deep to the brachioradialis muscle
ulnar n. medial cord of the brachial plexus unnamed muscular branches, palmar cutaneous br., dorsal br., superficial and deep brs. flexor carpi ulnaris m., flexor digitorum profundus m. (ulnar half), abductor digiti minimi m., flexor digiti minimi brevis m., opponens digiti minimi m., ulnar 2 lumbrical mm., palmar and dorsal interosseous mm. skin of the medial side of the wrist and hand; skin of the medial 1 1/2 digits ulnar n. is motor to most of the muscles of the hand

Arteries of the Forearm Flexor Region

Artery Source Branches Supply to Notes
anterior interosseous common interosseous a. muscular brs.; a. of the median nerve flexor pollicis longus m., flexor digitorum profundus m., pronator quadratus m., radius, ulna, carpal bones anterior interosseous a. pierces the interosseous membrane at its distal end to reach the dorsal carpal anastomosis
anterior ulnar recurrent ulnar a. unnamed muscular brs. medial side of elbow and proximal ends of forearm flexor mm. anterior ulnar recurrent a. often arises in common with the posterior ulnar recurrent a.
brachial axillary a. (brachial a. is the continuation of the axillary a. distal to the teres major m.) deep brachial a., superior ulnar collateral a., nutrient a., inferior ulnar collateral a.; terminal branches are the radial a. and the ulnar a. arm, forearm and hand brachial a. normally terminates by branching within the cubital fossa, but high branching may occur
common interosseous ulnar a. anterior interosseous a., posterior interosseous a. deep structures of the forearm common interosseous a. supplies the deep forearm flexor and deep forearm extensor muscles
interosseous recurrent posterior interosseous a. unnamed muscular branches anconeus m., elbow joint interosseous recurrent a. anastomoses with the middle collateral a.
posterior interosseous common interosseous a. interosseous recurrent muscles of the posterior (extensor) forearm compartment: supinator m., abductor pollicis longus m., extensor pollicis longus m., extensor pollicis brevis m., extensor indicis m. posterior interosseous a. passes proximal to the interosseous membrane to reach the extensor compartment of the forearm
posterior ulnar recurrent ulnar a. unnamed muscular branches medial side of the elbow, forearm flexor mm. posterior ulnar recurrent a. often arises from a common trunk with the anterior ulnar recurrent a.
radial brachial a. unnamed muscular branches in the proximal forearm; radial recurrent a., palmar carpal br., superficial palmar br., dorsal carpal br., 1st dorsal metacarpal a., princeps pollicis a., radialis indicis a., deep palmar arterial arch posterior elbow, posterior forearm, posterior hand, deep portion of palmar side of the hand, thumb radial a. provides the majority of blood supply to the deep palmar arterial arch; normally it arises at the level of the elbow but may high branching of the brachial a. may result in the radial a. arising as proximal as the axilla
radial recurrent radial a. unnamed muscular branches lateral side of the elbow and adjacent extensor muscles radial recurrent a. anastomoses with the radial collateral a.; it courses in the groove between the brachioradialis m. and the brachialis m.
ulnar brachial a. anterior ulnar recurrent a., posterior ulnar recurrent a., common interosseous a., palmar carpal br., dorsal carpal br., deep palmar br., superficial palmar arterial arch medial side of the anterior forearm, posterior forearm, superficial palm, fingers ulnar a. supplies the majority of blood to the superficial palmar arterial arch; it normally arises at the level of the elbow, but high branching of the brachial a. may cause the ulnar a. to arise as far proximally as the axilla

Joints - Radioulnar and Wrist

Joint or ligament Description Notes
elbow joint the joint between the distal humerus and the proximal radius and ulna a synovial hinge joint; the elbow joint is a complex joint consisting of humeroradial, humeroulnar and proximal radioulnar articulations all within a common articular capsule; it is strengthened by the ulnar and radial collateral ligaments
interosseous membrane, forearm a fibrous membrane that connects the interosseous borders located on the shafts of the radius and the ulna a syndesmosis; its fibers are oriented obliquely downward from the radius toward the ulna; the interosseous membrane is the classic example of a syndesmosis; proximally directed forces from the hand pass through the radius and are transferred to the ulna through the interosseous membrane; marked proximally by the oblique cord
radial collateral ligament, elbow a ligament spanning the lateral side of the elbow joint it connects the lateral epicondyle of the humerus with the radius and the annular ligament; it reinforces the lateral side of the elbow articular capsule; it is smaller and less distinct than the ulnar collateral ligament
radial collateral ligament, wrist it connects the styloid process of the radius with the scaphoid and trapezium it reinforces the articular capsule on the lateral side of the wrist
radiocarpal (wrist) joint synovial, chondyloid characterized by an intracapsular articular disk; radius articulates with the scaphoid and lunate bones which are members of the proximal row of carpal bones
radioulnar joint, distal the articulation between the head of the ulna and the ulnar notch of the radius a synovial pivot joint; this joint has a fibrocartilaginous articular disk that attaches to the styloid process of the ulna and the medial side of the distal radius
radioulnar joint, intermediate the articulation formed by the interosseous membrane a syndesmosis; it connects the interosseous border of the ulna to the interosseous border of the radius; proximally directed forces from the hand pass through the radius and are transferred to the ulna through the interosseous membrane
radioulnar joint, proximal the proximal articulation between the radius and ulna that is contained within the capsule of the elbow joint a synovial pivot joint; it is the articulation between the head of the radius and the radial notch of the ulna which is completed by the annular ligament
wrist joint the articulation between the distal end of the radius and the proximal row of carpal bones a synovial chondyloid joint; two primary planes of motion are permitted: abduction/adduction and flexion/extension - these motions are combined to produce circumduction; the radius actually articulates with the articular disk which in turn articulates with the scaphoid and lunate bones which are members of the proximal row of carpal bones

Fasciae of the Forearm

Structure Location/Description Notes
fascia, antebrachial deep fascia which forms a tubular investment of the forearm muscles antebrachial fascia is attached to the radius via the lateral intermuscular septum; it is attached to the subcutaneous border of the ulna
flexor retinaculum a thickening of the deep fascia on the ventral surface of the wrist flexor retinaculum spans the ventral surfaces of the carpal bones (medially - scaphoid and trapezium; laterally - hamate and pisiform) to complete an osseofibrous tunnel for passage of the flexor tendons; tendons are surrounded by synovial tendon sheathes where they pass deep to retinacula
palmar carpal ligament a thickening of the antebrachial fascia on the ventral surface of the wrist palmar carpal ligament is a retinaculum that supports the tendons of the superficial flexor mm.; it is superficial and proximal to the flexor retinaculum of the wrist


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Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of tables edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2005, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.

Unauthorized use is prohibited.