attachment points for many muscles of the neck, back, chest, and
between the ribs are occupied by
the intercostal muscles, which liF and then depress the thorax dur-
(breastbone) lies in the anterior midline of the tho-
rax. Vaguely resembling a dagger, it is a ﬂat bone approximately
15 cm (6 inches) long, resulting from the fusion of three bones: the
manubrium, the body, and the xiphoid process. Te
bre-um; “knife handle”) is the superior portion, which
is shaped like the knot in a necktie. Te manubrium articulates
u-lar) with the clavicles (col-
larbones) laterally, and just below this, it also articulates with the
ﬁrst two pairs of ribs. Te
, or midportion, forms the bulk of
the sternum. Te sides of the body are notched where it articu-
lates with the costal cartilages of the second to seventh ribs. Te
oid; “swordlike”) forms the inferior end of the
sternum. Tis small, variably shaped process is a plate of hyaline
cartilage in youth, but it is usually ossiﬁed in adults over the age of
40. Te xiphoid process articulates only with the sternal body and
serves as an attachment point for some abdominal muscles.
In some people, the xiphoid process projects posteriorly. In such
cases, blows to the chest can push the xiphoid into the underly-
ing heart or liver, causing massive hemorrhage.
Te sternum has three important anatomical landmarks: the jugu-
lar notch, the sternal angle, and the xiphisternal joint (±igure 7.23).
Te easily palpated
is the central in-
dentation in the superior border of the manubrium. If you slide your
ﬁnger down the anterior surface of your neck, it will land in the jugu-
lar notch. Te jugular notch is generally in line with the disc between
the second and third thoracic vertebrae and the point where the
leF common carotid artery issues from the aorta (±igure 7.23b).
(b) Midsagittal section through the thorax, showing
the relationship of surface anatomical landmarks
of the thorax to the vertebral column
(a) Skeleton of the thoracic cage, anterior view
The thoracic cage.
(For a related image, see
Atlas of the Human Body
, Figure 23a–d.)