Body of maxilla
From Wikipedia, the free encyclopedia
The body of the maxilla ('corpus maxillae') is somewhat pyramidal in shape, and contains a large cavity, the maxillary sinus (antrum of Highmore). It has four surfaces - an anterior, a posterior or infratemporal, a superior or orbital, and a medial or nasal.
Contents |
[edit] Anterior surface
The anterior surface [Fig. 1] is directed forward and lateralward. It presents at its lower part a series of eminences corresponding to the positions of the roots of the teeth. Just above those of the incisor teeth is a depression, the incisive fossa, which gives origin to the Depressor alae nasi; to the alveolar border below the fossa is attached a slip of the Orbicularis oris; above and a little lateral to it, the Nasalis arises.
Lateral to the incisive fossa is another depression, the canine fossa; it is larger and deeper than the incisive fossa, and is separated from it by a vertical ridge, the canine eminence, corresponding to the socket of the canine tooth; the canine fossa gives origin to the levator anguli oris (aka Caninus).
Above the fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital vessels and nerve.
Above the foramen is the margin of the orbit, which affords attachment to part of the Quadratus labii superioris.
Medially, the anterior surface is limited by a deep concavity, the nasal notch, the margin of which gives attachment to the Dilatator naris posterior and ends below in a pointed process, which with its fellow of the opposite side forms the anterior nasal spine.
[edit] Infratemporal surface
The infratemporal surface [Fig. 1] is convex, directed backward and lateralward, and forms part of the infratemporal fossa.
It is separated from the anterior surface by the zygomatic process and by a strong ridge, extending upward from the socket of the first molar tooth. It is pierced about its center by the apertures of the alveolar canals, which transmit the posterior superior alveolar vessels and nerves.
At the lower part of this surface is a rounded eminence, the maxillary tuberosity, especially prominent after the growth of the wisdom tooth; it is rough on its lateral side for articulation with the pyramidal process of the palatine bone and in some cases articulates with the lateral pterygoid plate of the sphenoid.
It gives origin to a few fibers of the internal pterygoid muscle (aka Pterygoideus internus). Immediately above this is a smooth surface, which forms the anterior boundary of the pterygopalatine fossa, and presents a groove, for the maxillary nerve; this groove is directed lateralward and slightly upward, and is continuous with the infraorbital groove on the orbital surface.
[edit] Orbital surface
The orbital surface [Fig. 1] is smooth and triangular, and forms the greater part of the floor of the orbit.
It is bounded medially by an irregular margin which in front presents a notch, the lacrimal notch; behind this notch the margin articulates with the lacrimal, the lamina papyracea of the ethmoid and the orbital process of the palatine.
It is bounded behind by a smooth rounded edge which forms the anterior margin of the inferior orbital fissure, and sometimes articulates at its lateral extremity with the orbital surface of the great wing of the sphenoid.
It is limited in front by part of the circumference of the orbit, which is continuous medially with the frontal process, and laterally with the zygomatic process.
Near the middle of the posterior part of the orbital surface is the infraorbital groove, for the passage of the infraorbital vessels and nerve. The groove begins at the middle of the posterior border, where it is continuous with that near the upper edge of the infratemporal surface, and, passing forward, ends in a canal, which subdivides into two branches.
One of the canals, the infraorbital canal, opens just below the margin of the orbit; the other, which is smaller, runs downward in the substance of the anterior wall of the maxillary sinus, and transmits the anterior superior alveolar vessels and nerve to the front teeth of the maxilla.
From the back part of the infraorbital canal, a second small canal is sometimes given off; it runs downward in the lateral wall of the sinus, and conveys the middle alveolar nerve to the premolar teeth.
At the medial and forepart of the orbital surface just lateral to the lacrimal groove, is a depression, which gives origin to the Obliquus oculi inferior.
[edit] Nasal surface
The nasal surface [Fig. 2] presents a large, irregular opening leading into the maxillary sinus. At the upper border of this aperture are some broken air cells, which, in the articulated skull, are closed in by the ethmoid and lacrimal bones.
Below the aperture is a smooth concavity which forms part of the inferior meatus of the nasal cavity, and behind it is a rough surface for articulation with the perpendicular part of the palatine bone; this surface is traversed by a groove, commencing near the middle of the posterior border and running obliquely downward and forward; the groove is converted into a canal, the pterygopalatine canal, by the palatine bone.
In front of the opening of the sinus is a deep groove, the lacrimal groove, which is converted into the nasolacrimal canal, by the lacrimal bone and inferior nasal concha; this canal opens into the inferior meatus of the nose and transmits the nasolacrimal duct. More anteriorly is an oblique ridge, the conchal crest, for articulation with the inferior nasal concha.
The shallow concavity above this ridge forms part of the atrium of the middle meatus of the nose, and that below it, part of the inferior meatus.
