The
sternum or breastbone or breastbone is an elongated, flattened bone, forming
the middle portion of the anterior wall of the thorax. Its upper end supports
the clavicles, and its margins articulate with the cartilages of the first
seven pairs of ribs. It consists
of three parts, named from above downward, the manubrium, the body
or gladiolus, and the xiphoid process; in early life the
body consists of four segments
sternum or breastbone or breastbone is an elongated, flattened bone, forming
the middle portion of the anterior wall of the thorax. Its upper end supports
the clavicles, and its margins articulate with the cartilages of the first
seven pairs of ribs. It consists
of three parts, named from above downward, the manubrium, the body
or gladiolus, and the xiphoid process; in early life the
body consists of four segments
or sternebrœ. In its natural position the
inclination of the bone is oblique from above, downward and forward. It is
slightly convex in front and concave behind; broad above,
becoming narrowed at the point where the manubrium joins the body, after which
it again widens a little to below the middle of the body, and then narrows to
its lower extremity. Its average length in the adult is about 17 cm., and is
rather greater in the male than in the female.
The Point of Ossification of the Sternum Bone
The sternum originally consists of two
cartilaginous bars, situated one on either side of the median plane and
connected with the cartilages of the upper ribs. These two bars fuse with each
other along the middle line to form the cartilaginous sternum which is ossified
from six centers:
cartilaginous bars, situated one on either side of the median plane and
connected with the cartilages of the upper ribs. These two bars fuse with each
other along the middle line to form the cartilaginous sternum which is ossified
from six centers:
- One for manubrium sterni: It appears
at the sixth month and rarely unites with other centers except at the old
age. - Four for the body: The first of these four appears at sixth
month, second and third at 7th month and fourth appears one year after
birth. They unite with each other after puberty. - One for the xiphoid process: It appears at 5th to 18th year of life but
remains partly cartilaginous.
