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
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
Crest of spine
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).
Medial border Lateral border
Ends of the
Fig.2.4: Fracture of clavicle
Fig. 2.5: Cleidocranial dysostosis
2 primary centres
Fig. 2.6: General features of right scapula: Dorsal surface