Human Anatomy Vol 1

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I

INTRODUCTION

Out of 206 totalbones in man, the upper limbs contain

as many as 64 bones. Each side consists of 32 bones,

the distribution of which is shown in Table 7.2 and

Fig. 1.1. The individual bones of the upper limb will be

described one by one. Their features and attachments

should be read with the bones before undertaking the

dissection of the part concerned. The paragraphs on

attachments should be revised when the dissection of

a particular region has been completed.

The clavicle (Latin a small key) is a long bone. It supports
the shoulder so that the arm can swing clearly away
from the trunk. The clavicle transmits the weight of the
limb to the sternum. The bone has a cylindrical part
called the shaft, and two ends,lateral and medial.

Side Delerminolion

The side to which a clavicle belongs can be determined
from the following characters.
1 The lateral end is flat, and the medial end is large
and quadrilateral.
2 The shaft is slightly curved, so that it is convex
forwards in its medial two-thirds, and concave
forwards in its lateral one-third.
3 The inferior surface is grooved longitudinally in its
middle one-third.

Peculiorilies of the Clovicle
1 It is the only long bone that lies horizontally.
2 It is subcutaneous throughout.
3 It is the first bone to start ossifying.
4 It is the only long bone which ossifies in membrane.
5 It is the only long bone which has two primary centres
of ossification.

6 There is no medullary cavity.

7 It is occasionally pierced by the middle supraclavicular

nerve.

It receives weight of upper limb via lateral one-third

through coracoclavicular ligament and transmits

weight of upper limb to the axial skeletal via medial

two-thirds part (see Flow chart 1.1).

Feotules

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The shaft (Figs 2.1a and b) is divisible into the lateral

one-third and the medial two-thirds.

Thelateral one-third of the shaft is flattened from above

downwards. It has two borders, anterior and posterior.

The anterior border is concave forwards. The posterior

border is convex backwards. This part of the bone has

two surfaces, superior and inferior.The superior surface

is subcutaneous and the inferior surface presents an

elevation called the conoid (Greek cone) tubercle and a

ridge called the trapezoid ridge.

The medial two-thirds of the shaft is rounded and

is said to have four surfaces. The anterior surface is

convex forwards. The posterior surface is smooth. The

superior surface is rough in its medial part. The inferior

surface has a rough oval impression at the medial end.

The lateral half of this surface has a longitudinal

subclaaian groooe.Thenutrient foramen lies at the lateral

end of the groove.

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(^1) The lateral or acromial (Greek peak of shoulder) end
is flattened from above downwards. It bears a facet
that articulates with the acromion process of the
scapula to form the acromioclavicular joint.
2 The medial or sternal end is quadrangular and
articulates with the clavicular notch of the
manubrium sterni to form the sternoclavicular joint.
The articular surface extends to the inferior aspect,
for articulation with the first costal cartilage.