Rib Characteristics And
Costovertebral Articulations
A typical rib has
a head, a neck, and a body. The head articulates with one or two vertebral bodies
(see below). A tubercle at the lateral end of the relatively short neck
articulates with the transverse process of the lower of the two vertebrae with
which the head of the rib articulates. As the body is followed anteriorly, the
“angle” of the rib is formed. At the inferior border of the body is the costal
or subcostal groove, partially housing the intercostal artery, vein, and nerve.
Each rib is continued anteriorly by a costal cartilage by which it is attached
either directly or indirectly to the sternum, except for the eleventh and
twelfth ribs, which have no sternal attachment.
The first and second ribs differ from the typical rib and therefore need
special description. The first rib— the shortest and most curved of all the
ribs—is quite flat, and its almost horizontal surfaces face roughly superiorly
and inferiorly. On its superior surface are grooves for the subclavian artery
and subclavian vein, separated by a tubercle for the attachment of the scalenus
anterior muscle.
The second rib is a good deal longer than the first, but its curvature is
very similar to the curvature of the first rib. The angle of the second rib,
which is close to the tubercle, is not at all marked. Its external surface
faces to some extent superiorly but a bit more outward than that of the first
rib.
The typical articulation of a rib with the vertebral column involves both
the head and tubercle of the rib. The head has two articular facets—the
superior facet making contact with the vertebral body above and the inferior
one with the vertebral body below. Between these, the head of the rib is bound
to the intervertebral disc by the intraarticular ligament. The articular facet
on the tubercle of the rib contacts the transverse process of the lower of the
two vertebrae. These are true or synovial joints, with articular cartilages,
joint capsules, and synovial cavities. The articulations of the first, tenth,
eleventh, and twelfth ribs are each with only one vertebra, the vertebra of the
same number.
The ligaments related to the typical articulation of a rib with the
vertebral column are as follows: for articulation
of the head of the rib, the intraarticular ligament and the capsular ligament,
with a thickening of its anterior part forming the radiate ligament; and for
the costotransverse joint, the thin capsular ligament, the lateral
costotransverse ligament between the lateral part of the tubercle of the rib
and the tip of the transverse process, and the superior costotransverse ligament
attached to the transverse process of the rib above.
The first and the last two (or three) ribs each has a single articular
facet that makes contact with an impression on the side of the thoracic
vertebra of the same number. No intraarticular ligament is present, so there is
just a single synovial cavity, in contrast to the two synovial cavities present
for the, typical rib. The lowest ribs do not have synovial joints between their
tubercles and the transverse processes of the related vertebrae.
