ANATOMY OF REGIONS. 
325 
which it joins after running through the ocular sheath ; second, the 
buccal vein, origin of the internal maxillary, which follows the inferior 
border of the alveolo labialis, in front of the curved portion of the an¬ 
terior border of the maxillary, between the last molar and the base of 
the coronoid process the alveolar vein and the buccal have such a di¬ 
ameter that their borders touch each other ; third, two large branches 
establish also a communication between the maxillo muscular and the 
buccal, and the temporal. These two anastomoses, as well as the buccal, 
are immediately resting on the maxillary. 
Nerves .—Aside the inferior maxillary nerve we find the facial, 
which makes its exit under the parotid with the temporal artery and 
veins. At this spot the facial has already made its union with the tem¬ 
poral trunk ; it constitutes the subzygomatic plexus, which radiates from 
that point to the antero inferior angle of the muscle. Its branches are 
then very numerous. Three or four are more principally noticed; one, 
the most anterior, mixes with the divisions of the superior maxillary 
nerve ; another goes to join the inferior coronary artery. 
B. ALVEOLO LABIAL REGION. 
Not as wide as the preceding, this region is limited forward by the 
line of insertion of the fibres of the alveolo labialis; below, by the 
commissure of the lips; behind, by the posterior border of the max¬ 
illary ; above, by the masseter muscle. 
Convex in the portion corresponding to the alveolo-labialis muscle, 
it presents a median fissure which defines the separation of the superior 
and inferior molar teeth. To the posterior border of the projection 
formed by the alveolo labialis, we notice that of the maxillo liabialis 
muscle*, under which pass the inferior coronary artery and vein. 
Under the thin and loose skin the cutaneous muscle mixes up 
its fibres with those of the superfical muscles of the region. These are, 
in front, the pyramidalis nasi, a little more behind the zygomaticus, yet 
more backwards a portion of the facial cutaneous, called in human 
anatomy the Risorius of Santorini. 
The third layer is formed by the buccinator, at the inferior border 
of which is found the maxillo labialis. It is to be noticed that the 
alveolo labialis is formed of two series of fibres which start from a 
median raphe, and which give the muscle a penniform aspect. We 
will place also in this third layer the extremity of the inferior and 
superior molar glands. The organs of this layer are immediately rest¬ 
ing on the buccal mucous membrane. 
* Depressor labii inferioris of Percival. 
