Palatine Bone

What is the Palatine Bone?

Palatine is one of the eight facial bones that constitute the facial skeleton or viscerocranium, along with others. This paired, irregular, L-shaped bone constitutes a portion of the hard palate, in addition to the nasal cavity and orbits.

Where Can the Palatine Bone Be Found?

The bone is situated between the maxillae and sphenoid bone, specifically between the palatine process of the maxillae and the pterygoid process of the sphenoid bone.

Key Points

Functions and Role

1. It contributes to the formation of the hard palate by connecting with the palatine process of the maxilla. This palate serves as the roof of the oral cavity and the floor of the nasal cavity.
2. The palatine also shapes the floor of the orbital cavity alongside the 6 other orbit bones.
3. The bone, together with the palatine process of the maxilla, gives rise to the lateral walls of the nasal cavity.

Structure

This bone consists of two plates, horizontal and perpendicular, that intersect at almost right angles, giving the bone its characteristic L-shape. It also comprises three processes: pyramidal, orbital and sphenoidal.

Horizontal Plate

As the name suggests, this quadrangular plate is the horizontal part of the bone, forming the base of the L-shaped bone. It contributes to the hard palate and nasal cavity. The horizontal plate includes four borders (medial, lateral, anterior, and posterior) and two surfaces (nasal and palatine).

Borders

1. Medial Border: The left and right palatine bones unite at their respective medial border, forming a median palatine suture.
2. Lateral Border: This border is a continuation of the perpendicular plate, housing the greater palatine foramen.
3. Anterior Border: The horizontal plate’s anterior border joins with the maxilla’s palatine process, collectively forming the hard palate.
4. Posterior Border: It faces the posterior wall of the pharynx.

Surfaces

1. Nasal surface: As the name suggests, it partially forms the posterior part of the nasal cavity’s floor and inferior nasal meatus.
2. Palatine surface: As the name suggests, it contributes to the hard palate. The surface includes two important foramina:
3. Greater palatine foramen: It is a small opening that permits the passage of greater and lesser palatine nerves running from the greater palatine canal and reaching the oral cavity. Along with these nerves, the descending palatine vessels course through this opening. The canal traverses the palatine and sphenoid bones, connecting the pterygopalatine fossa to the oral cavity. At the end, the canal gives rise to the lesser palatine canal.
4. Lesser palatine foramina: This foramen leads to the lesser palatine canal, conveying the lesser palatine vessels and nerves.

Perpendicular Plate

The perpendicular plate rises at an almost 90° angle with the lateral border of the horizontal plate, giving the bone its characteristic L-shape. It consists of several borders and surfaces.

Borders

Its 4 borders articulate with the adjacent bones and give rise to some essential bony landmarks.

1. Anterior border: It has a laminar projection to articulate with the inferior nasal concha, partly shaping the medial wall of the maxillary sinus.
2. Posterior border: This serrated border articulates with the medial pterygoid plate of the sphenoid bone.
3. Superior border: It connects with the body of the sphenoid bone. The border includes a deep notch, the sphenopalatine notch, between its orbital and sphenoidal processes. It remains enclosed by the sphenoid body, leading to the formation of the sphenopalatine foramen, which connects the pterygopalatine fossa with the nasal cavity.
4. Inferior border: This border is a continuation of the lateral border of the horizontal plate.

Surfaces

It includes two surfaces:

1. Nasal surface: This partly shapes the lateral wall of the nasal cavity, particularly the superoposterior part of the nasal septum. On its superior side, it connects with the cribriform plate of the ethmoid bone.
2. Maxillary surface: This primarily rough and irregular surface articulates with the nasal surface of the maxilla.

Processes

The bone comprises three main processes: pyramidal, orbital, and sphenoidal.

1. Pyramidal process: It emerges from the junction of horizontal and perpendicular plates, running between the medial and lateral pterygoid plates of the sphenoid bone. Its posterior surface joins with the pterygoid plates of the sphenoid bone to form a part of the pterygoid fossa.

2. Orbital process: This process originates anteriorly from the perpendicular plate. It includes three articular, two non-articular surfaces, and a narrow neck.

Articular surfaces

• Anterior or maxillary surface: It connects with the maxilla.
• Posterior or sphenoidal surface: It articulates with the sphenoid bone.
• Medial or ethmoidal surface: It articulates with the ethmoid bone.

Non-articular surfaces

• Superior or orbital surface: It partly shapes the floor of the eye cavity.
• Lateral surface: It also partially forms the pterygopalatine fossa.

3. Sphenoidal process: It extends from the upper part of the posterior border, forming a part of the pterygopalatine fossa. The medial border of this process forms a connection with the ala of the vomer.

Muscle Attachments

The four muscles that connect to this bone are:

1. Medial pterygoid muscle: It attaches to the pyramidal process.
2. Superior pharyngeal constrictor muscle: This muscle gets attached to the horizontal plate.
3. Tensor palate: This one also connects to the horizontal plate.
4. Uvula muscle: Another muscle that connects to the horizontal plate.

Ossification

The bone undergoes intramembranous ossification from a single center, which appears around the 6th–8th week of fetal life. The center first emerges at the junctional point of horizontal and perpendicular plates.

References

1. Palatine bone – Kenhub.com
2. Palatine bone – Radiopaedia.org
3. Palatine Bone – Sciencedirect.com
4. Palatine Bone Anatomy – Getbodysmart.com