2-23. THE STERNUM
a. Parts of the Sternum. The sternum, or breastbone (figure 2-24), is an
elongated, flattened bone situated in the median line in the front of the chest. It consists
of three parts, named: from top to bottom, the manubrium, the body or gladiolus, and
the ensiform process or xiphoid process. The superior border of the manubrium
presents three notches, the middle jugular or manubrial notch and two lateral clavicular
notches for the reception of the sternal ends of the clavicles. The inferior border of the
manubrium articulates with the superior border of the body of the sternum, forming an
angle (called the sternal angle or angle of Louis) that may be readily palpated. The
sternal angle marks the position of the second ribs, as well as the junction of the
manubrium, and the body of the sternum. The ensiform process, or xiphoid process,
the smallest of the three parts, varies much in form: it may be partly or wholly
cartilaginous, perforated by a foramen, broad and thin, pointed, bifid, deflected
considerably to one side or another, or inverted.
b. Articulations of the Sternum. The sternum articulates on either side with
the clavicle at the clavicular notch and with the upper seven costal cartilages at the
costal notches on the lateral border of the manubrium and the body (figure 2-24).
Figure 2-24. The sternum.