Page 281 - My FlipBook

THE NERVOUS SYSTEM. 291

The Snperio7' Set passes forward, and enters canals in the zygomatic
surface of the superior maxillary bone, traverses the base of the malar
process of this bone, and terminates in the canine fossa, interlacing with
the anterior dental nerves.
The Inferior Set is somewhat larger than the superior, and passes
downward, slightly outward and forward, to enter the posterior dental
canals. One of these canals traverses the outer wall of the maxillary
sinus, and joins the anterior dental canal extending from the infraorbital.
As the nerve passes forward in this canal it gives off branches which form
loops or plexuses, from which filaments are given off to enter the roots
of each of the molar teeth, and are distributed to their pulps, the outer
wall and mucous membrane of the maxillary sinus, the alveolar pro-
cess and the gums, and a few fibres to the bony structure of the antrum
of Highmore. Occasionally the posterior dental nerve is of large size,
and replaces an absent buccal nerve, a brancli of the inferior maxillary.
The Middle Superior Dental Nerve is given off from the infi-aor-
bital soon after it enters the infraorbital canal. It passes outward,
downward, and forward in a special canal in the outer wall of
the maxillary sinus, interlacing with the posterior dental nerve, and
forms loops or plexuses from which filaments are given off to enter the
roots of the bicuspid teeth.
The Anterior Superior Dental Nerve is larger than either of the other
two divisions. It is given off from the infraorbital nerve a little before
it emerges from the infraorbital foramen. It passes in a special canal
of its own which begins in the anterior wall of the maxillary sinus,
extends at first inward, then downward, and is reflected upon the floor
of the nasal fossa. It then passes in a lateral direction, and communi-
cates with the canals of the middle and posterior dental nerves. This
nerve gives off two sets of distributing branches, the ascending and the
descending.
The Ascending Nasal Set is distributed to the nasal spine of the supe-
rior maxillary bone, the mucous membrane of the anterior portion of
the inferior meatus, and to the floor of the nose.
The Descending or Dental Set is distributed through loops or plexuses
to the incisor and canine teeth, and interlaces with the middle and pos-
terior dental nerves.
The three superior dental nerves interlace or communicate with each
other in such a manner as to form loops or plexuses. These plexuses
(superior dental) are situated above the roots of the teeth, and it is
often, if not always, difficult to say where one begins and the other
ends. It is extremely probable that filaments from each of the three
nerves pass into the same tooth. This may account for the fact that
some of these nerves can be severed and the pulps of the teeth remain
vital.
The Facial or Terminal Set is composed of three nerves—the paljje-
bral, nasal, and labial. They arise from the infraorbital just
nerve emerges from the infraorbital foramen.
The Inferior Palpebral or Ascending Set is generally mj;
nerves. They ascend in a groove or canal, pass throup-^""
tion of the proper elevator muscle of the upper lip,