Left Clavicle Inferior Surface.
The posterior or cervical
surface is smooth, flat, and looks backward toward the root of the neck.
It is limited, above, by the superior border; below, by the subclavian
border; internally, by the margin of the sternal extremity; externally, it is
continuous with the posterior border of the flat portion. It is concave from
within outward, and is in relation, by its lower part, with the suprascapular
vessels. This surface, at about the junction of the inner and outer curves,
is also in close relation with the brachial plexus and subclavian vessels. It
gives attachment, near the sternal. extremity, to part of the Sterno-hyoid muscle;
and presents, at or near the middle, a foramen, directed obliquely outward,
which transmits the chief nutrient artery of the bone. Sometimes there are
two foramina on the posterior surface, or one on the posterior, the other on
the inferior surface
The inferior or subclaviansurface
is
bounded, in front, by the anterior border; behind, by the subclavian border.
It is narrow internally, but gradually increases in width externally, and
is continuous with the under surface of the flat
portion. Commencing at the sternal extremity may be seen a small facet for
articulation with the cartilage of the first rib. This is continuous with the
articular surface at the sternal end of the bone. External to this is a broad,
rough surface, the rhomboid impression, rather more than an inch in
length, for the attachment of the costo-clavicular (rhomboid) ligament. The
remaining part of this surface is occupied by a longitudinal
groove, the subclavian groove, broad and smooth externally, narrow and
more uneven internally; it gives attachment to the Subclavius muscle, and by
its margins to the costo-coracoid membrane, which splits to enclose a muscle.
Not infrequently this groove is subdivided into two parts by a longitudinal
line, which gives attachment to the intermuscular septum of the Subclavius
muscle.
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