Chapter 7
The Skeleton
227
7
into our mouth, we are making good use of our appendicular
skeleton.
The Pectoral (Shoulder) Girdle
Identify bones forming the pectoral girdle and relate their
structure and arrangement to the function of this girdle.
Identify important bone markings on the pectoral girdle.
Te
pectoral girdle
, or
shoulder girdle
, consists of the
clavi-
cle
(klav
9
ĭ-kl) anteriorly and the
scapula
(skap
9
u-lah) posteri-
orly (
Figure 7.25
and ±able 7.3 on p. 233). Te paired pectoral
girdles and their associated muscles form your shoulders. Al-
though the term
girdle
usually signifies a beltlike structure en-
circling the body, a single pectoral girdle, or even the pair, does
not quite satisfy this description. Anteriorly, the medial end of
each clavicle joins the sternum; the distal ends of the clavicles
meet the scapulae laterally. However, the scapulae fail to com-
plete the ring posteriorly, because their medial borders do not
join each other or the axial skeleton. Instead, the scapulae are
attached to the thorax and vertebral column only by the muscles
that clothe their surfaces.
Te pectoral girdles attach the upper limbs to the axial skel-
eton and provide attachment points for many of the muscles
Check Your Understanding
19.
How does a true rib differ from a false rib?
20.
What is the sternal angle and what is its clinical importance?
21.
Besides the ribs and sternum, there is a third group of bones
making up the thoracic cage. What is it?
For answers, see Appendix H.
PART 2
The Appendicular Skeleton
Bones of the limbs and their girdles are collectively called
the
appendicular skeleton
because they are appended to
the axial skeleton that forms the longitudinal axis of the
body (see Figure 7.1). Te yokelike
pectoral girdles
(pek
9
tor-
al; “chest”) attach the upper limbs to the body trunk. Te
more sturdy
pelvic girdle
secures the lower limbs. Although
the bones of the upper and lower limbs differ in their func-
tions and mobility, they have the same fundamental plan:
Each limb is composed of three major segments connected
by movable joints.
Te appendicular skeleton enables us to carry out the
movements typical of our freewheeling and manipulative life-
style. Each time we take a step, throw a ball, or pop a caramel
Clavicle
Acromio-
clavicular
joint
Scapula
(a) Articulated pectoral girdle
Acromial (lateral)
end
(b) Right clavicle, superior view
Posterior
Sternal (medial)
end
Anterior
Acromial end
Trapezoid line
Conoid tubercle
Anterior
Posterior
Sternal end
Right clavicle, inferior view
(c)
Figure 7.25
The pectoral girdle and clavicle.
(For a related
image, see
A Brief Atlas of the Human Body
, Figure 24.)
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