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Netter's Atlas Of Human Anatomy (5th Ed.).pdf
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FACTS & HINTS

HIGH-YIELD FACTS

Clinical Points

page 218

page 219

Fracture of the Clavicle

Common, especiallyin children

Usuallyresults from a fall on outstretched hand or direct trauma to the shoulder Fractures of middle third are most frequentlyseen

Sternocleidomastoid muscle pulls the proximal fragment superiorlyand the shoulder pulls the distal fragment inferiorly Small lump mayremain after the clavicle has healed

Calcific Supraspinatus Tendonitis

Inflammation and calcification of the subacromial bursa resulting in pain, tenderness and limitation of movement of the shoulder joint Calcium deposits frequentlyalso seen in the supraspinatus tendon

Pain is especiallysevere with the arm abducted between 50 to 130 degrees (the painful arc) as the supraspinatus tendon is in contact with the inferior surface of the acromion here

Shoulder Dislocation

High mobilityand instabilityof the glenohumeral joint leads to frequent dislocation

95% of dislocations are in anteroinferior direction, caused byexcessive extension and lateral rotation of humerus (e.g., in the throwing motion)

Humeral head places stress on joint capsule, which maybe torn anteriorly, with elements of the rotator cuff Axillaryand musculocutaneous nerves mayalso be injured

Posterior dislocation is uncommon, but mayoccur during epileptic seizure or electrocution

Rotator Cuff Injury

Musculotendinous rotator cuff maybe damaged bytrauma or degenerative disease

One or more of tendons maybe torn when the arm is forcefullyabducted, leading to pain in the anterosuperior aspect of the shoulder Supraspinatus tendon is most commonlyinvolved in degenerative tendonitis

Leads patient's arm to drop suddenlyat approximately90-degree abduction, when instructed to lower it slowlyfrom a fullyabducted position

MNEMONICS

Memory Aids

Rotator cuff muscles:

SITS = Supraspinatus, Infraspinatus, Teres minor, Subscapularis

343 / 425

45 Arm

STUDYAIMS

At the end of your study, you should be able to:

Identifythe different parts and surface markings of the humerus

Describe the organization of the deep fascia and compartments of the arm

Know the origins, insertions, and actions of the muscles of the arm

Know the cutaneous nerves of the arm

Describe the boundaries and contents of the cubital fossa

344 / 425

GUIDE

Upper Limb: Arm

[Plate 423, Arm: Serial Cross Sections]

Humerus

Largest bone of the upper limb

Osteological features

Head

Anatomical neck-circumscribes head above tubercles

Surgical neck: below tubercles-common site of fracture

Greater and lesser tubercles

Intertubercular groove

Bodywith

Deltoid tuberosityfor attachment of deltoid muscle

Radial groove on posterior surface where radial nerve and deep brachial arterytraverse

Medial and lateral supracondylar ridges-widening of humerus distallyas sharp ridges on either side

Medial epicondyle

Prominent medial extension at distal end

Common origin of forearm flexors; ulnar nerve posterior

Lateral epicondyle

Prominent lateral extension at distal end

Common origin of forearm extensors; radial nerve posterior

Condyle-distal end of humerus

Trochlea

Medial articular surface of condyle

For articulation with trochlear notch of ulna

Capitulum

Lateral articular surface of condyle

For articulation with head of radius

Coronoid fossa (see also Section 6-4: Upper Limb: Elbowand Forearm)

345 / 425

Superior to trochlea

Receives coronoid process of ulna

Olecranon fossae

Posterior distal end of humerus

Receives olecranon of ulna during full extension of forearm at elbow

page 220 page 221

Fascia of the Arm

Brachial fascia

Asleeve of deep fascia around the arm

Continuous with the antebrachial fascia of the forearm

Medial and lateral intermuscular septa

Extend from deep surface of brachial fascia to humerus

Divide arm into anterior (flexor) and posterior (extensor) compartments

Medial septum: medial lip of intertubercular sulcus (superiorly) → medial epicondyle

Lateral septum: lateral lip of intertubercular sulcus (superiorly) → lateral epicondyle

Muscles of the Arm

[Plate 419, Muscles of Arm: Anterior Views]

Anterior (flexor) compartment

Biceps brachii

Flexes and supinates

Continues distallyas bicipital aponeurosis: triangular membrane from the biceps tendon across cubital fossa and blends with antebrachial fascia over the flexor muscles of the forearm

Brachialis: main flexor of forearm

Coracobrachialis

Flexes and adducts arm

Pierced bythe musculocutaneous nerve Posterior (extensor) compartment

346 / 425

Triceps brachii

Main extensor of arm

Stabilizes head of humerus in glenohumeral joint

Anconeus: extends arm, and resists adduction of the ulna during pronation

Muscles

Origin

Insertion

Innervation

Blood supply

Action

Biceps brachii

Long head-supraglenoid tubercle of

Radial

Musculocutaneous

Muscular

Supinates

 

humerus; Short head-tip of coracoid process

tuberosity, fascia

nerve (C5,C6)

branches of

forearm

 

of scapula

of forearm via

 

brachial

Flexes

 

 

bicipital

 

artery

forearm when

 

 

aponeurosis

 

 

it is supinated

Coracobrachialis

Tip of coracoid process of scapula

Middle third of

Musculocutaneous

Muscular

Flexes and

 

 

medial surface

nerve (C5,C6,C7)

branches of

adducts arm

 

 

of humerus

 

brachial

 

 

 

 

 

artery

 

Brachialis

Distal half of anterior surface of humerus

Coronoid

Musculocutaneous

Radial

Flexes

 

 

process and

nerve (C5,C6)

recurrent

forearm

 

 

tuberosityof ulna

 

artery,

 

 

 

 

 

muscular

 

 

 

 

 

branches of

 

 

 

 

 

brachial

 

 

 

 

 

artery

 

Triceps brachii

Long head-infraglenoid tubercle of scapula;

Posterior

Radial nerve

Branch of

Extends

 

Lateral head -upper half of posterior

surface of

(C6,C7,C8)

profunda

forearm, long

 

humerus; Medial head -distal two thirds of

olecranon

 

brachii artery

head

 

medial and posterior humerus

process of ulna

 

 

stabilizes

 

 

 

 

 

head of

 

 

 

 

 

abducted

 

 

 

 

 

humerus

page 221 page 222

Cutaneous Nerves of Arm

Supraclavicular nerves (C4,C5) supplyskin over shoulder

Superior lateral cutaneous nerve (C5,C6)

Branch of axillary

Supplies skin over upper lateral arm

Inferior lateral cutaneous nerve (C5,C6)

Cutaneous branch of radial nerve

Supplies skin over lower lateral arm

Intercostobrachial nerve (T2)

Lateral cutaneous branch of second intercostal nerve

Supplies upper medial arm anteriorlyand posteriorly

Medial brachial cutaneous (C8-T1)

Branch of brachial plexus

Supplies lower anterior medial arm

Posterior brachial cutaneous nerve (C5-C8)

Branch of radial nerve

Supplies lower posterior medial arm

Cubital Fossa

Boundaries

Superiorly: (imaginary) line connecting the medial and lateral epicondyles

Medially: pronator teres muscle

Laterally: brachioradialis

Floor: brachialis and supinator muscles of arm and forearm

Roof: deep fascia, bicipital aponeurosis, subcutaneous tissue, and skin

Contents

Brachial artery(terminal part)

Biceps brachii tendon

Nerves: median

In subcutaneous connective tissue

Medial and lateral antebrachial cutaneous nerves

Basilic and cephalic veins

Median cubital vein

In floor of fossa

Deep and superficial branches of radial nerve

347 / 425

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