The The AntebrachiumAntebrachium

The The AntebrachiumAntebrachiumMaribel G. Castro, M.D.Maribel G. Castro, M.D.CPU College of MedicineCPU College of Medicine

The Cubital Fossa- A triangular hollow area on the anterior surface

of the elbow- Boundaries:

1. superior – imaginary line connecting the epicondyles

2. medial – pronator teres

3. lateral – brachioradialis

- Floor: brachialis and supinator muscles- Roof: deep fascia and bicipital aponeurosis

- covered by superficial fascia and skin

The Cubital FossaContents:1. Biceps tendon2. Brachial artery and its terminal branches

( radial and ulnar arteries)3. Brachial veins4. Parts on the median and radial nerves

Muscles in the Cubital Region

1. Pronator teres – medial border- has 2 heads of proximal attachment

- origin: medial epicondyle of humerus and conoid process of ulna

- insertion: middle of lateral surface of radius- action: pronates the forearm and flexes it

assists the pronator quadratus during pronation and is a weak flexor of the forearm

Muscles in the Cubital Region

2. Brachioradialis – lateral border- most superficial muscle on the radial side of

the forearm- origin: proximal 2/3 of supracondylar ridge of

humerus- insertion: lateral surface of distal end of

radius- action: flexes forearm especially when quick

movement is required or when a weight is lifted during slow flexion of the forearm

Muscles in the Cubital Region

3. Supinator – floor- lies deep in the cubital fossa- humeral and ulnar heads of attachment envelope

the neck and proximal part of the body of the radius- origin: lateral epicondyle of humerus, radial

collateral and annular ligaments, supinator fossa and crest of ulna

- insertion: lateral, posterior and anterior surfaces of proximal third of radius

- action: prime mover in supination of the forearm and hand

4. Brachialis - floor

Muscles of the ForearmA. Flexor/Volar/Anterior Surface 1. Superficial Group

a. pronator teres – prominent when the forearm is strongly flexed and pronatedb. flexor carpi radialis

- medial to the pronator teres- origin: medial epicondyle of humerus- insertion: base of 2nd metacarpal bone- action: flexes hand and abducts it- in the middle of the forearm, its fleshy belly

is replaced by a long, flattened tendon that becomes cordlike as it appraches the wrist

- tendon is a good guide to the radial artery which lies lateral to it

c. palmaris longus - small, fusiform muscle; is absent on one or both

sides (usually the left) in about 14% of people, but its actions are not missed

- origin: medial epicondyle of humerus- insertion: distal half of flexor retinaculum and

palmar aponeurosis- action: flexes hand and tightens palmar aponeurosis- its tendon is a useful guide to the median nerve

which passes lateral to itd. flexor carpi ulnaris

- most medial of the superficial of the flexors- has two heads b/n which the ulnar nerve passes - origin: humeral head – medial epicondyle

ulnar head – olecranon and posterior border of ulna

- insertion: pisiform bone, hook of hamate bone and 5th metacarpal bone

- action: flexes and adducts the the hand- tendon is a good guide to the ulnar nerve and artery

which are on its lateral side

2. Intermediate Groupa. flexor digitorum superficialis/sublimis

- largest superficial muscle in the forearm

- has 2 heads; forms an intermediate layer b/n the superficial and deep groups

- the ulnar and median nerves and the ulnar artery pass deeply between the heads

- near the wrist, gives rise to 4 tendons which pass deep to the flexor retinaculum where they are surrounded by a common flexor synovial sheath

- origin: humeroulnar head – medial epicondyle of humerus, ulnar collateral ligament, coronoid process of ulna

radial head – superior half of anterior border of radius

- insertion: bodies of the medial 4 digits

- action: flexes middle phalanges of medial 4 digits; acting more strongly, flexes proximal phalanges and hand

3. Deep Groupa. flexor digitorum profundus

- the only one that can flex the distal interphalangeal joints

- origin: proximal ¾ of medial and anterior surfaces of ulna and interosseous membrane

- insertion: bases of distal phalanges of medial 4 digits

- tendons pass posterior to the tendons of the flexor digitorum superficialis and the flexor retinaculum

- action: flexes the distal phalanges of the 2nd to 5th digits after the sublimis has flexed the middle phalanges

b. flexor pollicis longus- lies lateral to the flexor digitorum profundus

where it clothes the anterior aspect of the radius- passes deep to the flexor retinaculum,

enveloped in its own synovial sheath- origin: anterior surface of radius and adajcent

interosseous membrane- insertion: base of distal phalanx of thumb- action: flexes distal phalanx of thumb and

secondarily the proximal phalanx and 1st metacarpal bone

- only muscle that flexes the interphalangeal joint of the thumb

- also flexes the metacarpophalangeal joint and carpometacarpal joints of the thumb

- assists in wrist flexion

c. pronator quadratus- quadrangular muscle- deepest muscle in the anterior aspect of the forearm- clothes the distal 4th of the radius and ulna - origin: distal 4th of anterior surface of ulna- insertion: distal 4th of anterior surface of radius- action: pronates forearm at the superior and inferior radioulnar joints- prime mover in the pronation of the forearm- initiates pronation and assisted by the pronator teres when more speed and power are needed- deep fibers bind ulna and radius together

Muscles of the ForearmB. Extensor/Dorsal/Posterior

1. Superficial Groupa. brachioradialisb. extensor carpi radialis longus- partially overlapped by the brachioradialis with

which it is often blended- origin: lateral supracondylar ridge of humerus- insertion: base of 2nd metacarpal bone- action: extend and abduct the hand at the

wrist joint

c. extensor carpi radialis brevis- origin: lateral epicondyle of the humerus- insertion: base of 3rd metacarpal bone- action: extend and abduct hand at wrist joint- act together with the extensor carpi radialis

longus to steady the wrist during flexion of the medial 4 digits

d. extensor digitorum- principal extensor of the medial 4 digits- occupies much of the posterior surface of the

forearm- divides into 4 tendons proximal to the wrist which

pass through a common synovial sheath, deep to the extensor retinaculum

- origin: lateral epicondyle of humerus- insertion: extensor expansion of medial 4 digits- action: extends medial 4 digits at MCP joints;

extends hand at wrist joint; through its collateral reinforcements, extends the middle and distal phalanges

e. extensor digiti minimi- a partially detached part of the extensor

digitorum- its tendon runs through a separate

compartment in the extensor retinaculum and then divides into 2 slips; the lateral one is joined to the tendon of the extensor digitorum

- origin: lateral epicondyle of humerus- insertion: extensor expansion of 5th digit- action: extends digit 5 at MCP and IP joints;

f. extensor carpi ulnaris- has 2 heads- its tendon runs in a groove between the head

and styloid process of the ulna within a special compartment of the extensor retinaculum

- origin: lateral epicondyle of humerus and posterior border of ulna

- insertion: base of 5th metacarpal- action: extends and adducts hand at wrist joint

g. aconeus* part of the triceps and does not actually belong to

the posterior fascial compartment of the forearm, but for convenience and as is the custom , it is listed with it

2. Deep Group- consists of 3 muscles that act on the thumb (abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus) and the extensor indicis which help to extend the 2nd digit- anatomical snuff box

Boundaries:- anterior - abductor pollicis longus and extensor

pollicis brevis - posterior - tendon of extensor pollicis longus- floor – scaphoid and trapezium * scaphoid – most frequently fractured carpal

bone - injury to this results in localized

tenderness in the snuff box

a.abductor pollicis longus- lies just distal to the supinator muscle and is

closely related to the extensor pollicis brevis- origin: posterior surface of ulna and radius, and

interosseous membrane- insertion: base of 1st metacarpal bone- action: abducts thumb and extends it at

carpometacarpal joint- acts with the abductor pollicis brevis

during abduction of the thumb and with the extensor pollicis during extension of this digit

- its tendon passes deep to the extensor retinaculum in a common synovial sheath with the tendon of the extensor pollicis brevis

b. extensor pollicis brevis- lies distal to the long abductor of the thumb

and is partly covered with it- origin: posterior surface of radius and

interosseous membrane- insertion: base of proximal phalanx of thumb- action: extends proximal phalanx of thumb at

at carpometacarpal joint- helps to extend distal phalanx- in continued action, it helps to extend

the metacarpal bone of the thumb- helps to extend and abduct hand

c. extensor pollicis longus- origin: posterior surface of middle third of ulna and

interosseous membrane- insertion: base of distal phalanx of thumb- action: extends distal phalanx of thumb at MCP and IP

joints- adducts the extended thumb and rotates it

laterally; can also abduct hand

d. extensor indicis- lies medial and alongside the extensor pollicis longus- origin: posterior surface of ulna and interosseous

membrane- insertion: extensor expansion of second digit- action: extends digit 2 and helps to extend hand

- acting with extensor digitorum , it extends the finger at the proximal IP joint

e. supinator

Arteriesradial artery – smaller

Brachial artery branchulnar artery

1. Radial artery- trunk is not crossed by any muscle but the brachioradialis is lateral and overlaps it; flexor carpi radialis is medial in its distal 2/3- muscular branches supply muscles on the lateral side of the forearm- gives off the radial recurrent artery (supplies brachioradialis and brachialis m., and the elbow joint) which anastomoses with the radial collateral artery, a branch of the profunda brachii- at the wrist, covered only by superficial and deep fasciae and skin thus its pulsation can easily be felt- crosses the floor of the snuff box and ends by completing the deep palmar arterial arch in conjunction with the ulnar artery

1. radial artery cont….Branchesa. muscular branchesb. radial recurrent arteryc. superficial palmar branch

- arises at the distal end of the radius just proximal to the wrist

- supplies muscles of the thenar eminence- anastomoses with the terminal part of the

ulnar artery to form the superficial palmar arterial arch

d. palmar carpal branch- arises near the distal border of the pronator

quadratus- runs across the wrist deep to the flexor

tendons where it anastomoses with the carpal branch of the ulnar artery and recurrent branches of the deep palmar arch to form the palmar carpal arche. dorsal carpal branch

- runs medially across the dorsal surface of the wrist, deep to the extensor tendons

- anastomoses with the dorsal carpal branch of the ulnar artery and with terminations of the anterior and posterior interosseous arteries to form the dorsal carpal arch

2. ulnar artery- begins near the neck of the radius, just medial to the biceps tendon- in the forearm, passes deep to the fibrous arch of the flexor digitorum superficialis and crosses posterior to the median nerve- in the distal 2/3 of the forearm , the ulnar artery lies lateral to the ulnar nerve- leaves the forearm by passing superficial to the flexor retinaculum on the lateral side of the pisiform bone- at the wrist, the ulnar artery and nerve lie lateral to the tendon of the flexor carpi ulnaris- its pulse is not readily felt at the wrist because it is bridged by deep fascia ( the volar carpal ligament)

2. ulnar artery cont…- branches supply medial muscles in the forearm and hand, the common flexor synovial sheath and the ulnar nervea. anterior ulnar recurrent a.

- arises just inferior to the elbow runs superiorly between the brachialis and pronator teres which it supplies

- anastomoses with the inferior ulnar collateral a.b. posterior ulnar recurrent a.

- arises distal to the anterior ulnar recurrent a.- anastomoses with the superior ulnar collateral

a.- takes part in the arterial anastomoses around

the elbow

c. common interosseous a.- arises in the distal part of the cubital fossa and

divides into anterior and posterior branches1.) anterior interosseous artery

-passes distally on the interosseous membrane to the proximal border of the pronator quadratus

- pierces the membrane at the level of the pronator quadratus and continues distally to join the dorsal carpal arch

2.) posterior interosseous artery

- passes posteriorly b/n the bones of the forearm

- supplies adjacent muscles- gives off the posterior interosseous recurrent a.

which passes superiorly, posterior to the lateral epicondyle, and participates in the arterial anastomoses around the elbow

d. muscular branches- supply muscles on the medial side of the

forearm, mainly the flexor-pronator groupe. palmar carpal branch

- small branch running across the anterior aspect of the wrist, deep to the tendons of the flexor digitorum profundus

- anastomoses with the palmar carpal branch of the radial arterye. dorsal carpal branch

- arises just proximal to the pisiform bone- passes across the dorsal surface of the wrist

deep to the extensor tendons- anastomoses with the dorsal carpal branch of

the radial a.

f. superficial branch- continues into the palm as the

superficial palmar archg. deep palmar branch

- passes deeply in the hand- anastomoses with the radial artery and

completes the deep palmar arch

Nerves1. Median – principal nerve of the anterior

fascial compartment2. Ulnar3. Radial – enters the posterior compartment - Nerves of the anterior aspect of the forearm

are only 2 in number: the median and ulnar

1. Median Nerve- enters the forearm with the brachial artery

- brachialis b/n 2 heads of pronator teres flexor digitorum superficialis flexor digitorum profundus near the wrist becomes superficial b/n tendons of flexor digitorum superficialis and flexor carpi radialis, deep to the palmaris longus tendon- has no branches in the armBranchesa. articular branches – elbow jointb. muscular branches – pronator teres, pronator quadratus, and all flexors except flexor carpi ulnaris and the medial half of the flexor digitorum profundus (ulnar nerve)

c. anterior interosseous nerve- passes inferiorly on the interosseous

membrane with the anterior interosseous branch of the ulnar artery

- runs b/n the flexor digitorum profundus and flexor pollicis longus muscles to reach the pronator quadratus; supplies these 3 muscles

- ends by sending articular branches to the wrist jointd. palmar cutaneous branch

- supply the skin of the lateral part of the palm

2. Ulnar Nerve- passes posterior to the medial epicondyle b/n the 2 heads of the flexor carpi ulnaris descends deep to the flexor digitorum profundus (accompanies ulnar artery near the middle of the arm) medial side of ulnar artery and lateral side of flexor carpi ulnaris tendon distal part of forearm becomes realt6ively superficial covered only by fascia and skin pierces deep fascia and passes superficial to the flexor retinaculum with the ulnar artery, lateral to the pisiform between pisiform and hook of hamate (canal of Guyon – covered by a slip of flexor retinaculum)

Branchesa. articular branches

– elbow joint

- passes in the groove b/n the olecranon and medial epicondyle

b. muscular branches

– supply flexor carpi ulnaris and medial half of flexor digitorum profundus

c. palmar cutaneous branch

- arises from the ulnar nerve near the middle of the forearm and pierces the deep fascia in is distal third to supply skin on the medial part of palm

d. dorsal cutaneous branch

- arises from ulnar nerve in distal half of forearm and passes inferiorly b/n the ulna and flexor carpi ulnaris

- supplies posterior surface of medial part of hand

3. Radial Nerve- descends between brachialis and brachioradialis crosses anterior aspect of lateral epicondyle of humerus enters forearm divides into superficial and deep branches

Branchesa. superficial branch

- smaller of the 2 branches- direct continuation of the radial nerve- supplies skin on the dorsum of the wirst, hand,

thumb and lateral 1 ½ digits

b. deep branch- larger of the 2 terminal branches- entirely muscular and articular in its distribution- supplies extensor carpi radialis brevis, supinator- pierces the supinator muscle and curving around

the lateral side of the radius to enter the posterior fascial compartment of the forearm

- supplies extensor muscles- posterior interosseous n. – accompanies

posterior interosseous artery and supplies deep extensors

Gud PM