Page 222 - My FlipBook

232 ANATOMY

between the two heads of the external pterygoid muscle. This portion
has four branches, ^vhich supply the masticatorv and buccinator muscles.
They are named, according- to their distribution, the deep temporal,
pterygoid, masseteric, and buccal.
The Third or Spheno-maxillari/ Division extends from the inner sur-
face of the external pterygoid muscle to the termination of the artery
in the spheno-palatine fossa. It gives off six branches, each passing
into or througli osseous foramina. They are likewise named, according
to their course or the parts su])i)lied by them, the alveolar (or superior
maxillary), infraorbital, descending (superior) palatine. Vidian, pterygo-
palatine, and nasal or spheno-palatine.

ARTERIES OF THE FIRST DIVISION.
The Deep Auricular Branch is of small size, occasionally arising in
common with the tympanic branch, but usually it arises just external
to it, and perforates the anterior wall of the external auditory meatus.
It is distributed to the skin and the external portion of the tympanic
membrane.
The Ti/mpanic Artery is the second and one of the smallest branches
of tlie internal maxillary. It passes to the tympanum through the gle-
noid fissure (fissure of Glaser), and is distributed to the structures of the
middle ear and the tympanic membrane. It anastomoses with the stylo-
mastoid and Vidian arteries.
The Middle or Greed 3[eningeal Artery is the third and largest
bran ell. It is also the largest artery supplying the dura mater. It has
a calibre of about 2 mm. (Jj ii^t'h) and arises from the upper side ol'the
internal maxillary, passing upward behind and close to the insertion of
the external pterygoid muscle through a loop of the auriculo-teni])oral
nerve, and reaches the brain-case through the foramen spiuosum in the
spinous process of the great wing of the sphenoid bone. Within the
cranial cavity it passes in the direction of the anterior inferior angle of
the parietal bones along a groove anterior to and parallel with the
sjiheno-scjuamosal suture. When about midway of the suture it di-
vides into an anterior and a posterior branch. The anterior branch,
the larger of the two, passes across the outer and upper extremity of
the great wing of tlie sphenoid bone to the anterior inferior angle of the
parietal l)one, terminating in numerous branches which extend upward
and backward toward the inter])arietal suture. Occasionally the grooves
for the accommodation of this artery so deeply indent the bone as to be
eventually built over, thus forming canals. The posterior branch of the
great meningeal passes backward and upward along a groove, and crosses
the squamous portion of the tem])r)ral bone to the posterior half of the
imrietal bone, where it usually divides into two, the anterior l)ranch
ascending toward the vertex, while the other branch passes backward
toward the occipital bone.
The great meningeal artery before passing into the brain-case supplies
through its branches a portion of the pterygoid mus(^le and the tissue in
proximity to the foramen spiuosum. After entering the cranium it sup-
plies the dura mater, the bones, the diploe, the lachrymal gland, the