Anterior and posterior maxillary processes.—The anterior end of the anterior maxillary process (ant. max. proc.) lies within the maxillary at the level of the posterior terminus of the planum terminale. The anterior maxillary process diverges medially from the maxillary ([Fig. 13]) and expands dorsally along the medial face of the pars facialis to meet the planum antorbitale just anterior to the transition zone between the latter and the solum nasi. Posterior to the transition zone, the planum antorbitale disappears and the posterior maxillary process is restricted ventrally along the pars facialis of the maxillary. Posteriorly the cartilage is associated with the pterygoid, where it is known as the pterygoid process (pter. proc., [Fig. 14]).
Planum antorbitale.—The anterior terminus of the planum antorbitale (pla. ant.) lies medial to the ventrolateral part of the nasal and lateral to the internal nares ([Fig. 12]). It abruptly expands dorsally along the medial face of the nasal to join the tectum nasi dorsolaterally; somewhat posteriorly the planum antorbitale joins the anterior maxillary process ventrally at the posterior margin of the internal nares.
Figs. 10-11. Transverse sections through posterior part of olfactory capsule: 10) region of planum terminale; 11) anterior region of olfactory eminence. Abbreviations: cav. p., cavum principale; max., maxillary; nas., nasal; nlc. dt., nasolacrimal duct; olf. em., olfactory eminence; p. fac., pars facialis; p. pal., pars palatina; pla. ter., planum terminale; pvom., prevomer; rec. lat., recessus lateralis; sept. nas., septum nasi; sol. nas., solum nasi; tect. nas., tectum nasi.
External dermal bones associated with the olfactory region.—The association of the premaxillary (pmax.) to the nasal cartilages is described in preceding sections. The premaxillaries are separated from each other medially and from the maxillaries laterally by dense connective tissue. Anteriorly, the maxillary (max.) bears a small palatine process (pal. proc., [Fig. 1]) and a long, delicate pars facialis (p. fac., [Fig. 6]), which terminates dorsally at the level of the lamina inferior. Posterior to the transition zone between the planum antorbitale and solum nasi the pars facialis is greatly reduced. The pars palatina (p. pal., [Fig. 6]) persists to the posterior part of the orbit.
Fig. 12. Transverse section through the olfactory capsule in region of planum antorbitale. Abbreviations: cav. prin., cavum principale; int. nar., internal nares; max., maxillary; nas., nasal; olf. em., olfactory eminence; p. fac., pars facialis; p. pal., pars palatina; pal., palatine; pla. ant., planum antorbitale; pvom., prevomer; sept. nas., septum nasi; sol. nas., solum nasi; tect. nas., tectum nasi.
The anterior end of the prevomer (pvom., [Fig. 1]) is associated with the venter of the solum nasi at the level of the infundibulum just posterior to the incorporation of the inferior prenasal cartilage into the solum ([Fig. 7]). The prevomer expands dorsally around the distal end of the solum to provide a bony lateral support for the olfactory eminence ([Figs. 10 and 11]). A distal wing of the prevomer forms the bony anterior and medial margins of the internal nares.