Human Anatomy Vol 1

UPPER LIMB

f. The subclaztian vessels and cords of brachial plexus

pass towards the axilla lying between the inferior

surface of the clavicle and upper surface of first

rib. Subclavius muscle acts as a cushion.

The nutrient foramen transmits a branch of the

suprascapular artery.

The clavicle is the first bone in the body to ossify

(Fig. 2.3). Except for its medial end, it ossifies in

membrane. It ossifies from two primary centres and

one secondary centre.

The two primary centres appear in the shaft

between the fifth and sixth weeks of intrauterine life,

and fuse about the 45th day. The secondary centre

for the medial end appears during 1,5-17 years, and

fuses with the shaft during 21,-22years. Occasionally

there may be a secondary centre for the acromial end.

Fig. 2.3: Ossification

The clavicle is commonly fractured by falling on

the outstretched hand (indirect violence). The

most common site of fracture is the junction

between the two curvatures of the bone, which is

the weakest point. The lateral fragment is

displaced downwards by the weight of the limb

as trapezius muscle alone is unable to support the

weight of upper limb (Fig, 2.4).

The clavicles may be congenitally absent, or

imperfectly developed in a disease called

cleidocranial dysostosis. In this condition, the

shoulders droop, and can be approximated

anteriorly in front of the chest (Fi9.2.5).

Acromial process (acromion) with its medial border

Coracoid process

Suprascapular notch

Spinous process

Supraspinous fossa

Crest of spine

of scapula

Lateral

border

lnfraglenoid

tubercle

o
E

=o
CL
CL
f

o

Oo

a

The scapula (Latin shoulder) is a thin bone placed on

the posterolateral aspect of the thoracic cage. The

scapula has two surfaces, three borders, three angles,

and three processes (Fig.2.6).

lnfraspinous fossa

Medial border Lateral border

Trapezius

Ends of the

fractured

clavicle

Fig.2.4: Fracture of clavicle

Fig. 2.5: Cleidocranial dysostosis

2 primary centres

Fig. 2.6: General features of right scapula: Dorsal surface