Palate

Each palate bone, (os palati,) wedged in between the superior maxillary and sphenoid bones, is common to the cavity of the mouth, nares, and orbit. In its form, this bone somewhat resembles that of the letter l, one part being horizontal, the other vertical.

The horizontal or palate plate 1 of the bone, which is nearly square, and forms the back part of the roof of the mouth and of the floor of the nares, articulates anteriorly with the palate plate of the maxillary bone; internally it presents a rough thick border which rises up into a ridge, which joins with its fellow of the opposite side, and with it forms a groove which receives the lower border of the vomer; externally it unites at right angles with the vertical portion of the bone; posteriorly it presents a thin free border, forming the limit of the hard palate, and giving attachment to the velum or soft palate which projects downwards from it; it is slightly concave, and has at the inner angle a pointed process, 5 {the palate spine.) The superior surface of this plate or process is smooth, and forms the back part of the floor of the nasal cavity : the inferior, which forms part of the roof of the mouth, is unequal, and marked by a transverse ridge, into which the tendinous fibers of the circumflexus palati muscle are inserted; it presents also an oval foramen, being the inferior termination of the posterior palatine canal, which transmits the large descending palatine nerve and accompanying vessels; and farther back, another of smaller size, which transmits the middle palatine nerve.

At the junction of the horizontal and vertical portions is situated a thick rough tubercle 3 {tuberosity, pyramidal process,) projecting downwards and backwards. This is marked by three vertical grooves; the two lateral ones are rough, and receive the inferior borders of the pterygoid plates of the sphenoid bone; the middle one, smooth, corresponds with and completes the fossa between the pterygoid plates.

The vertical portion of the bone is flat and thin; it presents two surfaces; the internal one {nasal) is divided into two parts by a transverse ridge (crista transversa), which articulates with the inferior spongy bone; the space below the ridge forms part of the inferior meatus, that above it of the middle meatus. The external surface, rough and unequal, is divided by a vertical groove, which is completed into a canal {posterior palatine canal) by the maxillary bone.

The posterior part of this surface articulates with the rough border and nasal surface of the maxillary bone; and the anterior, thin and scale-like, with the side of the antrum.

The superior border of the vertical portion of the palate bone presents a notch, forming the greater part of a foramen, which is completed by the sphenoid bone when the parts are in their natural position. This is called the sphenopalatine foramen; and outside of it is placed the nervous ganglion of the same name (Meckel's ganglion). This notch divides the border of the bone into two processes or heads, the sphenoidal and the orbital.

The sphenoidal process, smaller and not so prominent, presents three surfaces, of which one, internal, looks to the nasal fossa; another, external, forms a small part of the zygomatic fossa; and the third, superior, grooved on its upper surface, articulates with the under surface of the sphenoid bone, and with it forms part of the pterygopalatine canal.

The orbital process inclines outwards and forwards, and has five surfaces, two of which are free, and three articulated; of the latter, the internal one rests against the ethmoid bone, and covers some of its cellules; the anterior articulates with the superior maxillary bone; and the posterior (which is hollow) with the sphenoid.

Of the non-articular surfaces, one superior, smooth and oblique, forms a small part of the floor of the orbit; the other, external, looks into the zygomatic fossa.

Articulations

With the corresponding palate bone; with the superior maxillary, ethmoid, sphenoid, vomer, and inferior spongy bone.

Muscular attachments

To its spine, the azygos uvulas; to the center groove on its tuberosity, a small part of the internal pterygoid; and to the transverse ridge on the palate plate, the aponeurosis of the circumflexus palati.

Ossification

The palate bone is formed from a single center, which is deposited at the angle formed between its parts. From this the ossification spreads in different directions — upwards into the vertical plate, inwards to the horizontal one, and backwards to the pyramidal process. For a considerable time after it has been fully ossified this bone is remarkable for its shortness; the horizontal plate exceeds in length the vertical one in the fetal skull.