Question

The most superior portion of the breastbone is called the __________.

Answer 1

Manubrium.
Breast bone means sternum .
The stemum is a flat bone, forming the anterior median
part of the thoracic skeleton. In shape, it resembles a
short sword. The upper part, corresponding to the
handle is called the manubrium. The middle part,
resembling the blade is called the body. The lowest
tapering part forming the point of the sword is the
xiphoid process or xiphisternum.   

The manubrium is quaddlateral in shape. It is the
thickest and strongest part of the sternum. It has two
surfaces, anterior and posterior; and four borders,
superior, inferior, and two lateral.
The  anterior surface is convex from side to side and
concave from above downwards .   
Theposterior surface is concave and forms the anterior
boundary of the superior mediastinum.
T}ne superior border is thick, rounded and concave. It
is marked by the suprasternal notch or jugular notch
or interclavicular notch in the median part, and by the
clavicular notch on each side. The clavicular notch
articulates with the medial end of the clavicle to form
the sternoclavicular joint .
The inferior border forms a secondary cartilaginous
joint with the body of the sternum. The manubrium
makes a slight angle with the body, convex forwards,
called t}ae sternal angle of Louis.
Thelateralborder forms a primary cartilaginous joint
with the first costal cartilage, and present a demifacet
for synovial articulation with the upper part of the
second costal cartilage.