The Back

Scapula, anterior aspect

Scapula-Posterior Aspect

TrapeziusOrigin• Occipital bone(external occiptal

protuberunce),superior nuchal line, ligamentum nuchae, spine of seventh cervical vertebra, spines of all thoracic vertebrae and their supraspinous ligament

Insertion• Upper fibers into lateral third of clavicle;

middle and lower fibers into acromion and spine of scapula

Nerve Supply• Spinal part of accessory nerve (motor) and

C3 and 4 (sensory)• XI cranial nerve (spinal part)

Action • Upper fibers elevate and upwardly rotate

the scapula, extend the neck.• middle fibers adduct(retracts) the scapula.• lower fibers depress and help upper fibres

in rotating scapula.

Latissimus dorsiOrigin• Iliac crest, lumbar fascia, spines

of lower six thoracic vertebrae(T7-T12), lower three or four ribs, and inferior angle of scapula

Insertion• Floor of bicipital groove of

humerus Nerve Supply• Thoracodorsal nerve(C6, 7, 8)Action• Extends, adducts, and medially

rotates the arm • Its called the climbing muscle• Raising of the trunk above the

armImportant :As it winds around lower

border of teres major it forms posterior fold of axilla its lateral border forms a boundary of lumbar triangle.

Levator scapulae

OriginTransverse processes of

first fourth cervical vertebrae

InsertionMedial border of scapula Nerve supplyC3 and 4 and dorsal

scapular nerveActionRaises medial border of

scapulaImportant : Part of floor

of Posterior triangle

Rhomboid minor and Major

Origin(MInor)Ligamentum

nuchae and spines of seventh cervical and first thoracic vertebrae

(Major)T2-T5 spinesInsertionMedial border of scapula Nerve supply• Dorsal scapular nerve

C4, 5Action• Raises medial border of

scapula upward and medially

DeltoidOriginLateral third

clavicle(Anterior)Lateral border of

acromion(middle) Spine of scapula(posterior)InsertionMiddle of lateral surface of

shaft of humerus to deltoid tuberosity

Nerve supplyAxillary nerve C5, 6ActionAnterior fibers flex and

medially rotate armMiddle fibers Abducts arm; Posterior fibers extend and

laterally rotate armAbduction from 15-90

degrees

Applied anatomy Intramuscular injections are

given into the deltoid .The should be given in the lower

half of the muscle to avoid injury to axillary nerve.

In subacromial bursitis pressure over the deltoid below the acromion with the arm by the side causes pain.

However when the arm is abducted pressure over the same point causes no pain because the bursa disappears under the acromion. This is referred to as Dawbarn’s sign.

SupraspinatusOriginSupraspinous fossa of

scapulaInsertionGreater tuberosity of

humerus; capsule of shoulder joint

Nerve supplySuprascapular nerve C4, 5, 6ActionAbducts arm and stabilizes

shoulder jointInitiation of abduction 0-15

degrees

InfraspinatusOriginInfraspinous fossa of

scapulaInsertionGreater tuberosity of

humerus; capsule of shoulder joint

Nerve supplySuprascapular nerve C4, 5, 6ActionLaterally rotates arm and

stabilizes shoulder joint

Teres minor

OriginUpper two thirds of lateral

border of scapulaInsertionGreater tuberosity of

humerus; capsule of shoulder joint

Nerve supplyAxillary nerve (C4), C5, 6ActionLaterally rotates arm and

stabilizes shoulder joint

Subscapularis

OriginSubscapular fossaInsertionLesser tuberosity of humerusNerve supplyUpper and lower subscapular

nerves C5, 6, 7ActionMedially rotates arm and

stabilizes shoulder jointImportant: Multipennate

Teres major

OriginLower third of lateral border of

scapulaInsertionMedial lip of bicipital groove of

humerusNerve supplyLower subscapular nerve C6, 7ActionMedially rotates and adducts arm

and stabilizes shoulder jointImportant : Considered

continuation of subscapularis

Rotator Cuff• The rotator cuff is the

name given to the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles

• Fused to the underlying capsule of the shoulder joint

• The cuff lies on the anterior, superior, and posterior aspects of the joint

• The cuff is deficient inferiorly, and this is a site of potential weakness.

Quadrangular Space Superiorly by the

subscapularis and capsule of the shoulder joint

Inferiorly by the teres major muscle

Medially by the long head of the triceps

laterally by the surgical neck of the humerus.

Contents The axillary nerve and

the posterior circumflex humeral vessels

Upper & Lower Triangular spaces

Upper Superiorly subscapularis

and teres minor Inferiorly teres major Laterally the long head of

the triceps • Contains circumflex

scapular vessels.Lower superiorly the teres

major medially long head of the

triceps brachii laterally Medial head of

triceps• Contains radial nerve and

profunda brachii artery.

The triangle of auscultation

• It is the site where breathing sounds can be heard most clearly, using a stethoscope.

Is formed by the vertebral or medial border of the scapula,

superior border of latissimus dorsi

the lateral border of the trapezius. It has a floor formed by

rhomboid major. It covers the intercostal space

between ribs 6 and 7 and rib 7. It lies superficial to the cardiac

orifice of the stomach on the left side, where splash of swallowed liquids was timed in cases of esophageal obstruction.

It is the site where breathing sounds can be heard most clearly, using a stethoscope.

The lumbar triangle

Is formed by the posterior free border of

the external oblique, the superior border of the

iliac crest and the lateral border of the

latissimus dorsi.• Its floor if formed by

internal oblique abdominal muscle.

• It may be site of an abdominal hernia.

Axillary Nerve Arises from the posterior

cord of the brachial plexus (C5 and 6) in the axilla

Passes backward ,through quadrangular space with the posterior circumflex humeral artery

In close association with surgical neck of humerus and capsule of shoulder joint

It terminates by dividing into anterior and posterior branches

Branches

Articular branch to the shoulder joint

Anterior terminal branch supplies the deltoid and the skin that covers its lower part.

Posterior terminal branch supplies teres minor muscle and deltoid, then emerges as the upper lateral cutaneous nerve of the arm

Applied Aspect

• The axillary nerve may be damaged by

dislocation of shoulder or by fracture of surgical neck of humerus.

• The patient presents with loss of abduction of shoulder upto 90 degrees (as deltoid is paralysed), loss of rounded countour of shoulder and sensory loss over lower deltoid.

Suprascapular nerve The suprascapular nerve originates from Upper trunk of the brachial plexus

It passes through suprascapular foramen to reach the posterior scapular region

innervates the supraspinatus muscle

then passes through the greater scapular (spinoglenoid) notch

Terminate in and innervate the infraspinatus muscle.

Mnemonic(“Army over and navy under the bridge”)

Arterial Anastomosis Around the Shoulder Joint

Branches from the subclavian artery

1. The suprascapular artery is a branch of thyrocervical trunk of subclavian artery.

Supplies the supraspinous and infraspinous fossae, and their contents .

2. Deep branch of transverse cervical artery supplies the rhomboidei and the medial border of the scapula, running deep to levator scapulae.

Branch from the axillary artery3. The circumflex scapular artery, a

branch of the subscapular artery which arises from the third part of axillary artery

Applied aspect • Scapular anastomoses is an

anastomoses between the first part of subclavian and third part of axillary artery. So it provides a collateral circulation through which blood can flow to the limb in case of blockage of distal part of subclavian artery or proximal part of axillary artery.