Pectoral girdle

pectoral muscles

Pectoralis major

Origin

· clavicular head

· medial half of clavicle anteriorly

· sternocostal head

· lateral part of manubrium and sternum

· upper 6 costal cartilages

Path

· forms tendon that folds on itself

Insertion

· via trilaminar tendon

· into lateral lip of bicipital groove

· clavicular head

· forms anterior lamina

· extends up to surgical neck

· manubrial part of sternocostal head

· forms intermediate lamina

· sternocostal part of sternocostal head

· forms posterior lamina

· fibres which arise lowest insert highest

· extends up to capsule of shoulder joint

Nerve supply

· clavicular head

· C(5,)6

· by lateral pectoral nerve

· sternocostal head

· C7,8(,T1)

· by medial pectoral nerve

Pectoralis minor

Origin

· 3rd, 4th and 5th ribs

Path

· lies under pectoralis major

· pierced by medial pectoral nerve

Insertion

· coracoid process

· medial part

Nerve supply

· medial pectoral nerve

Subclavius

Origin

· costochondral junction of 1st rib

Path

· lies under clavicle

· enclosed by upper attachment of clavipectoral fascia

Insertion

· subclavian groove of clavicle

Nerve supply

· nerve to subclavius from C5 and C6 roots

clavipectoral fascia

· fills space between clavicle and pectoralis minor

· medial to coracoid

· superiorly

· attaches to anterior and posterior parts of subclavian groove on underside of clavicle

· splits to enclose subclavius

· may form band under subclavius called costocoracoid ligament

· laterally

· limited by coracoid process

· medially

· fuses with external intercostal membrane of upper 2 spaces

· inferiorly

· splits to enclose pectoralis minor

· rejoins below to join suspensory ligament of axilla

· pierced by

· in - lymphatics and cephalic vein

· out - thoracoacromial vessels and lateral pectoral nerve

shoulder muscles

Trapezius

Origin

· occipital

· medial 1/3 of superior nuchal line

· ligamentum nuchae

· spine of C7

· thoracic

· spines of T1-T12

Path

· converges to narrow tendon

Insertion

· occipital fibres

· lateral third of clavicle posteriorly

· upper thoracic fibres (T1-T6)

· medial border of acromion

· superior lip of scapular spine

· as far as deltoid tubercle

· lower thoracic fibres (T6-T12)

· narrow tendon into medial end of spine of scapula

Nerve supply

· spinal part of accessory nerve C1-5

Latissimus dorsi

Origin

· spines of T7-S5

· ridge on posterior part of crest of ilium

· with posterior layer of lumbar fascia

· posterior third of outer lip of iliac crest

Path

· converges into narrow tendon

· upper fibres pass horizontally

· over inferior border of scapula

· lower fibres pass vertically

· reinforced by slips from lower 4 ribs

· forms posterior axillary border

· fibres spiral around teres major

· anterior fibres become posterior

Insertion

· floor of bicipital groove

· by 2.5 cm tendon

Nerve supply

· thoracodorsal nerve (C6,7,8) from posterior cord

Levator scapulae

Origin

· posterior tubercles (true transverse processes) of C1-4

Insertion

· upper angle of scapula

Nerve supply

· cervical plexus (C3,4) and dorsal scapular nerve from C5 root

Rhomboid minor

Origin

· spines of C7 and T1

Insertion

· medial border of scapula above base of spine

Nerve supply

· dorsal scapular nerve from C5 root

Rhomboid major

Origin

· spines of T2-5

Insertion

· medial border of scapula

· by fibrous arch from inferior border to base of spine

Nerve supply

· dorsal scapular nerve from C5 root

Serratus anterior

Origin

· digitations from upper 8 ribs

· 1st digitation from outer surface of 1st rib

Path

· forms medial wall of axilla

· upper digitation appears in posterior triangle

· neurovascular bundle passes over 1st digitation

Insertion

· along vertebral border of costal surface of scapula

· upper 2 digitations

· upper angle

· middle 2 digitations

· vertebral border

· lower 4 digitations

· inferior angle

Nerve supply

· long thoracic nerve from roots of C5,6,7

· upper 2 - C5

· middle 2 - C6

· lower 4 - C7