Each maxilla is composed of five parts. Besides the central part known as the body, the maxilla has the following four processes:

Frontal process

The frontal process is a vertical extension of the maxilla that projects upward, medially and slightly backward. It is positioned between the nasal and lacrimal bones and contributes to the formation of the lacrimal fossa. As the name suggests, it also articulates with the frontal bone. Besides the mentioned bones, the frontal process also connects with the ethmoid.

The frontal process of the maxilla features the following landmarks:

Anterior lacrimal crest - a vertical ridge that is found on the lateral aspect of this process; it limits the lacrimal groove anteriorly and continues as the infraorbital margin in the lateral direction;
Ethmoidal crest - a short obliquely-oriented ridge that is found on the medial aspect of the frontal process going more or less parallel to the conchal crest; it articulates with the ethmoid;
Lacrimal notch - an indentation that defines the superior border of the lacrimal groove; it is found in the posterolateral aspect of this process.

Zygomatic process

The zygomatic process is the short lateral extension of the maxilla that articulates with the zygomatic bone. The orbital, infratemporal and anterior surfaces of the body meet at the zygomatic process.

Palatine process

The palatine process (palatal process) is a thick, horizontally oriented medial extension of the maxilla. It is shaped like a horizontal plate and forms the anterior three-quarters of the hard palate. Therefore, this process contributes to the formation of the roof of the oral cavity and the floor of the nasal cavity. It features the following landmarks:

Nasal crest - a sagitally-oriented ridge that forms from the fusion of both maxillae; it is found on the superior aspect of the palatine process, and it extends into the nasal cavity and articulates with the vomer;
Incisive foramen - opening that is found on the inferior aspect of the palatine process at the anterior end of the medial border posterior to the medial incisors; the incisive foramen leads to two lateral incisive canals that transmit the nasopalatine nerves, sphenopalatine arteries and the terminal branches of the greater palatine arteries; the incisive canals connect the nasal and oral cavities;
Palatine grooves - numerous shallow grooves that are found on the inferior surface of the palatine process;
Palatine spines - small bony prominences that are found between the palatine grooves.

Alveolar process

The alveolar process is the inferior horseshoe-shaped extension of the maxilla. It forms the maxillary dental arch and houses the maxillary teeth (the lower jaw or mandible also has an alveolar process).

The curved free inferior margin of the alveolar process is called the alveolar arch. It features the following landmarks:

Dental alveolus - eight sockets or cavities that house the roots of the teeth; their dimensions and structures vary depending on the teeth type;
Interalveolar septum - a bony ridge between adjacent dental alveoli;
Interradicular septum - a bony ridge that forms compartments within one dental alveolus; within those compartments lie the roots of the particular tooth;
Alveolar yoke - bony eminence on the outer surface of the alveolar process; they are produced by the projections of the dental alveoli and the roots of the teeth.

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Upper jaw (processes of maxilla)