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2 Surfaces 3 Borders 4 The Vertical Part 5 The Pyramidal Process or Tuberosity 6 The Orbital Process 7 The Sphenoidal Process 8 Ossification 9 Articulations |
The Horizontal Part
The horizontal part (pars horizontalis; horizontal plate) [Fig. 1&2] is quadrilateral, and has two surfaces and four borders.Surfaces
The superior surface, concave from side to side, forms the back part of the floor of the nasal cavity. The inferior surface, slightly concave and rough, forms, with the corresponding surface of the opposite bone, the posterior fourth of the hard palate. Near its posterior margin may be seen a more or less marked transverse ridge for the attachment of part of the aponeurosis of the Tensor veli palatini.
Figure 1 : Left palatine bone. Nasal aspect. Enlarged. |
Figure 2 : Left palatine bone. Posterior aspect. Enlarged. |
The maxillary surface is rough and irregular throughout the greater part of its extent, for articulation with the nasal surface of the maxilla; its upper and back part is smooth where it enters into the formation of the pterygopalatine fossa; it is also smooth in front, where it forms the posterior part of the medial wall of the maxillary sinus. On the posterior part of this surface is a deep vertical groove, converted into the pterygopalatine canal, by articulation with the maxilla; this canal transmits the descending palatine vessels, and the anterior palatine nerve.
The orbital and sphenoidal processes are separated from one another by the sphenopalatine notch. Sometimes the two processes are united above, and form between them a complete foramen [Fig. 1], or the notch may be crossed by one or more spicules of bone, giving rise to two or more foramina.
This article is based on an entry from the 1918 edition of Gray's Anatomy, which is in the public domain. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.The Vertical Part
The vertical part (pars perpendicularis; perpendicular plate) [Fig. 1&2] is thin, of an oblong form, and presents two surfaces and four borders.Surfaces
The nasal surface exhibits at its lower part a broad, shallow depression, which forms part of the inferior meatus of the nose. Immediately above this is a well-marked horizontal ridge, the conchal crest, for articulation with the inferior nasal concha; still higher is a second broad, shallow depression, which forms part of the middle meatus, and is limited above by a horizontal crest less prominent than the inferior, the ethmoidal crest, for articulation with the middle nasal concha. Above the ethmoidal crest is a narrow, horizontal groove, which forms part of the superior meatus.Borders
The anterior border is thin and irregular; opposite the conchal crest is a pointed, projecting lamina, the maxillary process, which is directed forward, and closes in the lower and back part of the opening of the maxillary sinus. The posterior border [Fig. 2] presents a deep groove, the edges of which are serrated for articulation with the medial pterygoid plate of the sphenoid. This border is continuous above with the sphenoidal process; below it expands into the pyramidal process. The superior border supports the orbital process in front and the sphenoidal process behind. These processes are separated by the sphenopalatine notch, which is converted into the sphenopalatine foramen by the under surface of the body of the sphenoid. In the articulated skull this foramen leads from the pterygopalatine fossa into the posterior part of the superior meatus of the nose, and transmits the sphenopalatine vessels and the superior nasal and nasopalatine nerves. The inferior border is fused with the lateral edge of the horizontal part, and immediately in front of the pyramidal process is grooved by the lower end of the pterygopalatine canal.
The Pyramidal Process or Tuberosity
The pyramidal process (processus pyramidalis) projects backward and lateralward from the junction of the horizontal and vertical parts, and is received into the angular interval between the lower extremities of the pterygoid plates. On its posterior surface is a smooth, grooved, triangular area, limited on either side by a rough articular furrow. The furrows articulate with the pterygoid plates, while the grooved intermediate area completes the lower part of the pterygoid fossa and gives origin to a few fibers of the Pterygoideus internus. The anterior part of the lateral surface is rough, for articulation with the tuberosity of the maxilla; its posterior part consists of a smooth triangular area which appears, in the articulated skull, between the tuberosity of the maxilla and the lower part of the lateral pterygoid plate, and completes the lower part of the infratemporal fossa. On the base of the pyramidal process, close to its union with the horizontal part, are the lesser palatine foramina for the transmission of the posterior and middle palatine nerves.
The Orbital Process
The orbital process (processus orbitalis) is placed on a higher level than the sphenoidal, and is directed upward and lateralward from the front of the vertical part, to which it is connected by a constricted neck. It presents five surfaces, which enclose an air cell. Of these surfaces, three are articular and two non-articular. The articular surfaces are:
In some cases the air cell opens on this surface of the bone and then communicates with the posterior ethmoidal cells. More rarely it opens on both surfaces, and then communicates with the posterior ethmoidal cells and the sphenoidal sinus. The non-articular surfaces are:
The Sphenoidal Process
The sphenoidal process (processus sphenoidalis) is a thin, compressed plate, much smaller than the orbital, and directed upward and medialward. It presents three surfaces and two borders. The superior surface articulates with the root of the pterygoid process and the under surface of the sphenoidal concha, its medial border reaching as far as the ala of the vomer; it presents a groove which contributes to the formation of the pharyngeal canal. The medial surface is concave, and forms part of the lateral wall of the nasal cavity. The lateral surface is divided into an articular and a non-articular portion: the former is rough, for articulation with the medial pterygoid plate; the latter is smooth, and forms part of the pterygopalatine fossa. The anterior border forms the posterior boundary of the sphenopalatine notch. The posterior border, serrated at the expense of the outer table, articulates with the medial pterygoid plate.Ossification
The palatine bone is ossified in membrane from a single center, which makes its appearance about the sixth or eighth week of fetal life at the angle of junction of the two parts of the bone. From this point ossification spreads medialward to the horizontal part, downward into the pyramidal process, and upward into the vertical part. Some authorities describe the bone as ossifying from four centers: one for the pyramidal process and portion of the vertical part behind the pterygopalatine groove; a second for the rest of the vertical and the horizontal parts; a third for the orbital, and a fourth for the sphenoidal process. At the time of birth the height of the vertical part is about equal to the transverse width of the horizontal part, whereas in the adult the former measures about twice as much as the latter.Articulations
The palatine articulates with six bones: the sphenoid, ethmoid, maxilla, inferior nasal concha, vomer, and opposite palatine.