Palatine boneThe palatine bone is a paired bone located between the maxillae and the pterygoid process of the sphenoid bone. It participates in building the three cavities within the skull; the oral cavity, nasal cavity and the orbits. It does so by articulating with five bones; maxilla, sphenoid, ethmoid, inferior nasal concha, and vomer. Moreover, the palatine bone contributes to the skeletal framework of the inferior orbital fissure, pterygopalatine and pterygoid fossae.
The palatine bone is composed of two plates, the horizontal and perpendicular, which are connected and form a characteristic L-shape bone. The bone features three processes; pyramidal, orbital and sphenoidal.
This article will discuss the anatomy and function of the palatine bone.
|Parts||Horizontal plate, perpendicular plate, pyramidal process, orbital process, sphenoidal process|
|Landmarks||Median posterior nasal spine, greater palatine groove, greater palatine canal, sphenopalatine notch|
|Function||Participates in the formation of the:
- Horizontal plate
- Perpendicular plate
- Clinical aspects
The horizontal plate of palatine bone is located in the transverse plane. It comprises the bony core of the posterior quarter of the hard palate and a part of the floor of the nasal cavity. The plate is quadrangular in shape, having a medial, lateral, anterior, and posterior border. It shows two surfaces, the palatine and nasal, which face the oral and nasal cavities respectively.
- The medial border of the horizontal plate articulates with the horizontal plate of the contralateral palatine bone. From the nasal side, the articulating line between the two plates forms the posterior part of the nasal crest, which articulates with the vomer.
- The lateral border of the horizontal plate is continuous with the perpendicular plate. It features the greater palatine foramen through which the greater palatine nerve and vessels pass.
- The anterior border articulates with the palatine process of maxilla. Together, the horizontal plate of palatine bone and the maxilla comprise the hard palate.
- The posterior border faces the posterior wall of the pharynx. The medial ends of the posterior surfaces of both horizontal plates together form a bony projection in the midline, called the median posterior nasal spine. This spine serves as an attachment site for the uvular muscle.
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The perpendicular plate of palatine bone continues from the lateral margin of the horizontal plate. It bears this name as it forms a 90° angle with the horizontal plate, giving the noticeable L-shape to the palatine bone. The perpendicular plate has two surfaces, nasal and maxillary and 4 borders, anterior, posterior, superior, and inferior.
The nasal surface of the perpendicular plate faces the nasal cavity, forming a part of its lateral wall. The inferior part of this surface is marked by a concavity that contributes to the inferior nasal meatus. Superior to this is the conchal crest, via which it articulates with the inferior nasal concha. Above this crest there is a shallow concavity that comprises a part of the middle nasal meatus. Superior to this concavity is the ethmoidal crest, onto which the middle nasal concha attaches.
The maxillary surface of the perpendicular place articulates with the nasal surface of the maxilla. It is mostly rough and irregular, except in its posterosuperior and anterior portions. The posterosuperior smooth area forms the medial wall of the pterygopalatine fossa, while the anterior smooth area forms the posterior portion of the medial wall of the maxillary sinus. The maxillary surface is also marked by an oblique groove called the greater palatine groove. It transmits the structures which pass through the greater palatine foramen. The adjacent surface of the maxilla closes this groove, converting it into the greater palatine canal, which transmits the greater palatine nerve, artery and vein.
The borders of the perpendicular plate serve for the articulations with the neighboring bones.
- The anterior border shows a laminar projection at the level of the conchal crest that articulates with the inferior nasal concha and forms a part of the medial wall of the maxillary sinus.
- The posterior border is serrated and it articulates with the medial pterygoid plate of the sphenoid bone. The sphenoidal process continues from the superior part of the posterior border, whilst the pyramidal process continues from its inferior part.
- The superior border articulates with the body of the sphenoid bone. It is marked by the sphenopalatine notch, which is closed superiorly by the sphenoid body and converted into the sphenopalatine foramen. This foramen is a connection between the pterygopalatine fossa and superior nasal meatus, transmitting the posterior superior nasal nerves and sphenopalatine vessels between them. The anterior part of the superior border projects into the orbital process of the palatine bone.
- The inferior border of the perpendicular plate is continuous with the lateral border of the horizontal plate.
The pyramidal process of the palatine bone arises from the junction between the horizontal and perpendicular plates. It is oriented posterolaterally, passing between the medial and lateral pterygoid plates of the sphenoid bone. The posterior surface of this process articulates with the pterygoid plates, forming the inferior part of the pterygoid fossa. The lateral surface provides the attaching site for the superficial head of the medial pterygoid muscle, while the inferior surface features the lesser palatine foramina for the passage of the lesser palatine nerves and vessels.
The orbital process originates from the anterior part of the orbital margin of the perpendicular plate. It is directed superiorly and slightly anteriorly, coursing towards the floor of the orbit. This process shows a narrow neck, three articular, and two non-articular surfaces.
- The anterior (maxillary) surface is directed anteriorly and laterally and it articulates with the maxilla.
- The posterior (sphenoidal) surface faces superiorly and posteromedially andt is marked by an opening of an air sinus that is contained within this process, via which this sinus communicates with the sphenoidal sinus.
- The medial (ethmoidal) surface courses anteriorly and medially. It articulates with the labyrinth of the ethmoid bone. In some individuals, this surface is the one that contains an opening of the air sinus instead of the posterior surface. In this case, the bone communicates with the posterior ethmoidal air cells rather than with the sphenoidal sinus.
The two non-articular surfaces of the orbital process are the superior (orbital) and lateral. The superior (orbital) surface forms a part of the floor of the bony orbit, while the lateral surface forms a part of the pterygopalatine fossa. These two surfaces are separated by a notch that forms the medial part of the inferior border of the inferior orbital fissure.
The sphenoidal process courses superomedially from the superior part of the posterior border of the perpendicular plate.
- Its superior surface articulates with the sphenoidal concha and the root of the medial pterygoid plate. This surface is also marked by a groove that forms a part of the palatovaginal canal.
- The inferomedial surface is concave and it forms a part of the floor and lateral wall of the nasal cavity.
- The lateral surface contributes to the part of the medial wall of the pterygopalatine fossa.
The sphenoidal process has three borders. The posterior border articulates with the medial pterygoid plate, while the medial border articulates with the ala of the vomer. The anterior border forms the posterior margin of the sphenopalatine notch.
The greater and lesser palatine nerves, found in the horizontal plate and the pyramidal process of the palatine bone respectively, are quite sensitive. This is why they need to be anesthetized before the extraction of the upper premolars and molars. For this procedure the needle is inserted on the medial side of the (adult) second molar, 1 cm from the gingival margin. Hereby the dentist ought to be careful not to use too much force and penetrate the greater palatine foramen.