Download Anatomy Exam 3 Lecture 17-Brachium and Shoulder: Two types of

Anatomy Exam 3
Lecture 17-Brachium and Shoulder:
 Two types of movement occur between arm and forearm at elbow:
o Flexion and Extension
o Pronation and Supination
 Anterior Compartment (Flexors)
o Innervated by musculocutaneous nerve (C5-C7)
 Pierces coracobrachialis
 Lies deep to biceps brachii and emerges along lateral aspect of the
cubital fossa and becomes the lateral antebrachial cutaneous nerve of
the forearm.
o Biceps Brachii
 Proximal attachment:
 Short headtip of coracoid process
 Long headsupraglenoid tubercle of scapula
 Distal Attachment:
 Tuberosity of radius and fascia of forearm
 Actions:
 Supinates forearm
 Flexes forearm when supine
 Rupture of the tendon of the long head results in ‘Popeye deformity.’
Associated with a pop or snap, muscle belly forms ball near the center,
anterior aspect of the arm.
 Results from forceful flexion against excessive weight (weight
lifters)
 Also results from repetitive overhead motions that tear
weakened tendon.
o Brachialis
 Proximal attachment:
 Distal half of anterior surface of humerus
 Distal attachment:
 Coronoid process and tuberosity of ulna
 Action:
 Flexes forearm in all positions
o Coracobrachialis
 Proximal attachment:
 Tip of coracoid process of scapula (short head of biceps and
pectoralis minor also attach to coracoid process).
 Distal attachment:
 Middle third of medial surface of humerus
 Action:
 Flexion of arm
 Adduction of arm
 Resists downward dislocation of the head of the humerus.
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Posterior Compartment (Extensor)
o Innervated by radial nerve
o Triceps Brachii
 Proximal attachment:
 Long headInfraglenoid tubercle of scapula
 Lateral headPosterior surface of humerus, superior to radial
groove
 Medial headPosterior surface of humerus, inferior to radial
groove
 Distal attachment:
 Proximal end of olecranon of ulna and fascia of forearm.
 Action:
 Medial headforearm extension
 Long headStabilizes adducted glenohumeral joint, extends
arm at the shoulder.
o Anconeus also in posterior compartment
 Proximal attachment:
 Lateral epicondyle of humerus
 Distal attachment:
 Lateral surface of olecranon and superior part of posterior
surface of ulna
 Action:
 Assists triceps with extension of forearm, stabilizes elbow.
Vasculature of brachium
o Axillary artery becomes brachial artery at teres major.
 1st branch is the profunda brachial artery, deep artery of the arm.
Travels posterior to humerus in radial groove with radial nerve.
 Terminates and splits into middle collateral artery (goes to
back) and connects to the recurrent interosseous artery; and
the radial collateral artery (comes to front) and connects to the
recurrent radial artery.
 Superior and inferior ulnar collateral arteries branch off of brachial
artery.
 Superior ulnar collateral a. goes posterior to medial epicondyle
and anastomoses with the posterior ulnar recurrent artery and
the inferior ulnar collateral artery
 Inferior ulnar collateral a. goes anterior to medial epicondyle
and anastomoses with anterior recurrent ulnar artery.
o In the cubital fossa, the brachial artery terminates and splits into the radial
artery (lateral) and the ulnar artery (medial).
o Nutrient artery penetrates the bone and supplies the medullary cavity.
o Brachial a. can be physically compressed to stop bleeding, by pressing into
the medial aspect of the humerus.
o Two main superficial veins of the arm:
 Cephalic vein
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 Basilic vein.
o Brachial vein accompanies the brachial a., called vena comitans. Merging of
basilica vein and brachial vein forms the axillary vein.
Nerves of the arm:
o Musculocutaneous nerve, pierces coracobrachialis and becomes the lateral
cutaneous nerve in the cubital fossa.
 Damage to musculocutaneous nerve can result in paralysis of the
coracobrachialis, biceps, and brachialis.
 Flexion of elbow and supination of forearm are weakened, but not
lost.
o Radial nerve innervates all muscles in the posterior compartment of the arm
and forearm (extension).
 Travels with profunda brachial a. and passes around humeral shaft in
radial groove.
 When the radial nerve reaches the lateral border of the humerus, it
continues inferiorly in the anterior compartment of arm between the
brachialis and brachioradialis.
 Radial nerve divides into deep branch (muscular) and superficial
branch (cutaneous).
 Injury to radial nerve superior to triceps brachii branches, results in
paralysis of triceps, brachioradialis, supinator and extensor muscles
of wrist and fingers.
 Injury to radial nerve in radial groove, triceps is weakened but not
paralyzed. Muscles in posterior compartment of forearm are
paralyzed. Results in wrist drop, unable to extend wrist and fingers at
MP joints.
o Median nerve has no branches in axilla or arm.
o Ulnar nerve passes posterior to medial epicondyle and medial to olecranon
to enter forearm. Referred to as the ‘funny bone.’ Has no branches in arm.
Lecture 18-Elbow and Forearm:
 Cubital fossa-depression on anterior aspect of elbow.
o Terminal part of brachial artery and beginning of terminal branches: radial
and ulnar arteries.
o Median nerve and radial nerve pass through here.
 Fascia of the forearm- forms the flexor retinaculum (converts anterior concavity of
the wrist into carpal tunnel, that contains 9 tendons and 1 nerve).
 In forearm: flexors lie anteriorly and extensors lie posteriorly.
o Medial epicondyle provides attachment for forearm flexors.
 Flexors and pronators innervated by median nerve (one and a half
exceptions by ulnar nerve)
o Lateral epicondyle provides attachment for forearm extensors.
 Extensors and supinators are all innervated by radial nerve.
 Flexor-Pronator Muscles
o Superficial Layer (4 muscles)
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Pronator teres-lateral border forms the medial boundary of cubital
fossa.
 Proximal attachment:
o Ulnar headcoronoid process
o Humeral headmedial epicondyle
 Distal attachmentmiddle of convexity of lateral surface of
radius
 Innervation: Median nerve
 Actions:
o Pronates forearm
o Flexes forearm
 Disorders: pronator syndrome results from nerve entrapment.
Median nerve passes between the two heads and can be
compressed.
Flexor carpi radialis-located medial to pronator teres.
 Proximal attachmentcoronoid process
 Distal attachmentbase of 2nd metacarpal
 Innervation: Median nerve
 Actions:
o Flexes hand at wrist, when acting with flexor carpi
ulnaris
o Abducts hand at wrist, when acting with extensors carpi
radialis longus and carpi radialis brevis.
Palmaris longus-may be absent, lies medial to flexor carpi radialis.
 Proximal attachmentMedial epicondyle
 Distal attachmentdistal half of flexor retinaculum and apex
of palmar aponeurosis
 Innervation: Median nerve
 Actions:
o Flexes hand at wrist
o Tenses palmar aponeurosis
Flexor carpi ulnaris-most medial of superficial flexor muscles. Ulnar
nerve enters forearm by passing between humeral and ulnar heads at
proximal attachment.
 Proximal attachment
o Humeral headmedial epicondyle
o Ulnar headolecranon and posterior border
 Distal attachmentpisiform, hook of hamate, and 5th
metacarpal.
 Innervation: Ulnar nerve
 Actions:
o Flexes hand at wrist and adducts hand at wrist
simultaneously.
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Disorder: ulnar nerve may be compressed or entrapped,
causing cubital tunnel syndrome. Causes pain in 4th and 5th
metacarpal and medial aspect of palm.
o Intermediate layers (1 muscle)
 Flexor digitorum superficialis-gives rise to four tendons that pass
through carpal tunnel.
 Proximal attachment
o Humeroulnar headmedial epicondyle
o Radial headsuperior half of anterior border
 Distal attachmentshafts of middle phalanges of medial four
fingers.
 Innervation: median nerve
 Actions:
o Flexes middle phalanges at PIP of middle four fingers.
o Flexes proximal phalanges at MP joint.
o Deep Layer (3 muscles)
 Flexor digitorum profundus-dually innervated
 Proximal attachmentproximal ¾ of medial and anterior
surfaces of ulna and interosseous membrane.
 Distal attachmentbases of distal phalanges of 4th and 5th
fingers
 Innervation
o Medial partulnar nerve
o Lateral partanterior interosseous nerve (from median
nerve)
 Actions
o Medial partflexes distal phalanges 4 and 5 at DIP
o Lateral partflexes distal phalanges 2 and 3 at DIP
 Flexor pollicis longus-long flexor of the thumb
 Proximal attachmentanterior surface of radius and adjacent
interosseous membrane
 Distal attachmentbase of distal phalanx of thumb
 Innervation: Anterior interosseous nerve
 Actionflexes phalanges of thumb
 Pronator quadratus-initiates pronation
 Proximal attachmentdistal quarter of anterior surface of
ulna
 Distal attachmentdistal quarter of anterior surface of radius
 Innervation?
 Actions
o Pronates forearm
o Deep fibers bind radius and ulna together.
o Colles fracture is the most common fracture of the forearm; distal radius fx
and the ulna styloid.
Extensor Muscles (posterior compartment)
o Brachioradialis-functionally a flexor, located in posterior compartment
 Innervated by radial nerve
 Does not cross wrist and incapable of acting on it.
o Extend and ab/adduct the hand at the wrist:
 Extensor carpi radialis longus-partly overlapped by brachioradialis,
often blends.
 Proximal attachmentlateral supraepicondylar ridge
 Distal attachmentdorsal aspect of base of 2nd metacarpal
 Innervated by radial nerve
 Action: works with ECRB to abduct and extend the hand
simultaneously.
 Extensor carpi radialis brevis-shorter than longus, and covered by
longus.
 Proximal attachmentlateral epicondyle
 Dorsal attachmentdorsal aspect of base of 3rd metacarpal
 Innervated by radial nerve
 Action: works with ECRL to abduct and extend the hand
simultaneously.
 Extensor carpi ulnaris-long muscle located on the medial border of
the forearm.
 Proximal attachmentlateral epicondyle
 Distal attachmentdorsal aspect of base of 5th digit
 Innervated by radial nerve
 Action:
o Acting with ECRL and ECRB it extends the hand.
o Acting with the flexor carpi ulnaris it adducts the hand.
o Extend the medial four fingers:
 Extensor digitorum-principal extensor of the medial four fingers.
Adjacent tendons are linked proximal by three oblique intertendinous
connections.
 Distal attachmentfour tendons flatten to form extensor
expansions, that attach to MP joints of all 5 metacarpals.
 Innervation by radial nerve.
 Extensor indicis-lies deep to extensor digitorum tendon of index
finger.
 Proximal attachmentposterior surface of distal third of ulna
and interosseous membrane
 Distal attachmentextensor expansion of 2nd digit
 Innervated by radial nerve.
 Actionindependent extension of index finger at PIP.
 Extensor digit minimi-partially detached part of extensor digitorum
 Tendon divides into two slips, the lateral one is joined to distal
tendon of extensor digitorum.
 Proximal attachmentcommon extensor tendon
 Distal attachmentdistal expansion of 5th digit
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Innervation by radial nerve
Actionextends 5th digit.
o Supinator
 Sheet-like muscle envelops the neck and proximal part of the shaft of
the radius.
 Deep branch of radial nerve passes through muscle fibers, and
becomes the posterior interosseous nerve.
 Proximal attachmentlateral epicondyle, radial collateral and
annular ligaments, supinator fossa, and crest of ulna.
 Distal attachmentlateral, posterior, and anterior surfaces of
proximal third of radius.
 Actionprime mover for slow, unopposed supination.
o Extend or abduct the thumb
 Abductor pollicis longus-lies distal to supinator.
 Proximal attachmentposterior surface of proximal halves of
ulna, radius and interosseous membrane.
 Distal attachmentbase of 1st metacarpal
 Innervated by radial nerve
 Actionabducts 1st digit
 Extensor pollicis brevis-lies distal to APL and is partly covered by it
 Proximal attachmentposterior surface of distal third of
radius and interosseous membrane
 Distal attachmentdorsal aspect of base of proximal phalanx
of thumb
 Innervated by radial nerve
 Actionextends 1st digit
 Extensor pollicis longus
 Proximal attachmentposterior surface of middle third of ulna
and interosseous membrane
 Distal attachmentdorsal aspect of base of distal phalanx of
thumb
 Innervated by radial nerve
 Action-extends 1st digit.
o Anatomical snuff box made by extensor pollicis longus tendon, extensor
pollicis brevis tendon, and abductor pollicis longus tendon.
 Radial artery and scaphoid lies in the floor.
o Elbow tendinitis (lateral epicondylitis or tennis elbow).
 Repetitive use of the superficial extensor muscles of the forearm.
 Repeated forceful flexion and extension of the wrist.
Ulnar nerve is located on medial side of ulnar artery.
Common Interosseous Artery:
o Short branch of ulnar artery arises in distal part of cubital fossa.
o Divides into anterior and posterior interosseous arteries.
 Anterior interosseous artery passes distally and runs with anterior
interosseous nerve.
Posterior interosseous artery courses between superficial and deep
layers of extensor muscles with the posterior interosseous nerve.
 Posterior interosseous nerve is coming of the radial nerve.
 Anterior interosseous nerve is coming off of median nerve.
Median nerve injury
o Unable to flex digits 1-3.
Ulnar nerve injury
o Claw hand from ulnar nerve injury, causes atrophy of interosseous muscles,
unable to flex fingers.
Radial Tunnel Syndrome-resistant form of tennis elbow, results from entrapment of
deep branch of radial nerve.
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