General structure and body of the bone
The maxilla is one of the main paired bones of the facial skull. Anatomically, it comprises a central part — the body (corpus maxillae) — and four branching processes.
A crucial feature of the body is that it contains a spacious air-filled cavity inside: the maxillary sinus, or antrum of Highmore (sinus maxillaris). The opening to this cavity is called the maxillary hiatus (hiatus maxillaris) and is located on the nasal aspect of the bone. In the intact skull, this wide opening is partially covered by adjacent bony structures, specifically the middle nasal concha.
Surfaces of the body of the maxilla
The body of the bone has four distinct surfaces, each of which contributes to forming important topographical regions of the skull:
- Orbital surface (facies orbitalis) — forms the inferior wall of the orbit. It features a distinct infraorbital groove (sulcus infraorbitalis), which smoothly transitions into the infraorbital canal (canalis infraorbitalis). This canal opens on the facial aspect via the infraorbital foramen (foramen infraorbitale), located in the area of the canine fossa (fossa canina).
- Anterior surface (facies anterior) — bounded superiorly by the infraorbital margin (margo infraorbitalis). Medially, it transitions into the nasal notch (incisura nasalis), and inferiorly, at the very anterior edge, it projects as the anterior nasal spine (spina nasalis anterior).
- Infratemporal surface (facies infratemporalis) — dominated by the prominent maxillary tuber (tuber maxillae, or eminentia maxillae). This eminence features alveolar foramina (foramina alveolaria) leading to alveolar canals (canales alveolares). Through these canals, vessels and nerves supply the roots of the molars and premolars.
- Nasal surface (facies nasalis) is bounded anteriorly by the lacrimal sulcus (sulcus lacrimalis). In the middle, the opening into the maxillary sinus is visible, and posteriorly runs the greater palatine sulcus (sulcus palatinus major), which together with the corresponding sulcus of the palatine bone forms the greater palatine canal.
Frontal and zygomatic processes
Four processes attach to the body. The first two are directed superiorly and laterally:
- Frontal process (processus frontalis). Its medial surface faces the nasal cavity, forming its lateral wall. Here are located the ethmoidal crest (crista ethmoidalis) and conchal crest (crista conchalis) for articulation with the ethmoid bone and the inferior nasal concha. Lateral surface faces the orbit, forming its medial wall. It features the anterior lacrimal crest (crista lacrimalis anterior) and lacrimal margin (margo lacrimalis), which transitions into the lacrimal notch (incisura lacrimalis).
- Zygomatic process (processus zygomaticus). This is a relatively simple bony structure without prominent fine details. Its primary function is to provide a secure articulation with the zygomatic bone.
Alveolar and palatine processes
The remaining two processes are intrinsically connected with the oral cavity and the masticatory apparatus:
- Alveolar process (processus alveolaris). Participates in forming the alveolar arch (arcus alveolaris). It contains depressions — dental alveoli (alveoli dentales) — where the tooth roots are anchored. The sockets are separated from each other by interalveolar septa (septa interalveolaria). If a tooth is multi-rooted (molars), there are also interradicular septa (septa interradicularia) within the alveolus. On the outer surface of the process, the root contours form raised alveolar juga (juga alveolaria).
- Palatine process (processus palatinus). Forms the anterior two-thirds of the hard palate. On its nasal surface (facies nasalis) extends the nasal crest (crista nasalis), which ends posteriorly in the posterior nasal spine (spina nasalis posterior). On the palatine surface (facies palatina), one can find the palatine spines (spinae palatinae) and palatine sulci (sulci palatini). In the anterior part of the process run the incisive canals (canales incisivi), which most commonly fuse and open into the incisive foramina (foramina incisiva). In some cases, the anterior segment may exist as an independent structure — the incisive part (os incisivum, or premaxilla). In this variant, the incisive suture (sutura incisiva).
Briefly: answers to topical questions
What passes through the infraorbital canal?
The infraorbital vessels and the nerve of the same name pass through the infraorbital canal.
- Infraorbital artery (A. infraorbitalis) — a branch of the maxillary artery.
- Infraorbital vein (V. infraorbitalis) — drains into the inferior ophthalmic vein or the pterygoid venous plexus.
- Infraorbital nerve (N. infraorbitalis) — the terminal branch of the maxillary nerve (the second branch of the trigeminal nerve).
Which bones does the frontal process of the maxilla articulate with?
The frontal process of the maxilla articulates with the ethmoid bone and the inferior nasal concha: its medial surface features the ethmoidal and conchal crests, which are sites of articulation with these structures.
What passes through the incisive canal?
The nasopalatine vessels and nerve pass through the incisive canal, heading from the nasal cavity to the hard palate.
- Nasopalatine nerve (N. nasopalatinus) — a branch of the maxillary nerve (the second branch of the trigeminal nerve).
- Nasopalatine artery (A. nasopalatina).
- Nasopalatine vein (V. nasopalatina).
What bones cover the maxillary hiatus in the intact skull?
In the intact skull, the maxillary hiatus (Hiatus maxillaris) is covered by the middle nasal concha and adjacent structures. It is located in the middle of the nasal surface of the maxillary body and serves as the entrance to the maxillary (Highmore's) sinus. An exact and complete list of all bones covering this entrance is not provided in these materials.
Which muscles originate from or attach to the maxilla?
Facial muscles attach to the anterior wall of the maxilla. Each of these muscles has its own loose fascial sheath, with communicating layers of adipose tissue located between them. Specific names of individual facial or other muscles that originate or attach directly to the bony structures of the maxilla are not detailed in the provided materials.
Memorizing the 4 processes of the maxilla is easy using the acronym ZFAN: Zygomatic, Frontal, Alveolar, Palatine.
Class and exam questions
To which division of the skull does the maxilla belong?
The maxilla belongs to the facial skull (viscerocranium) and is a paired bone.
What is located inside the body of the maxilla?
Inside lies a large air-filled cavity — the maxillary sinus, or antrum of Highmore (sinus maxillaris).
Through which foramina do nerves and vessels approach the upper posterior teeth?
They pass through the alveolar foramina (foramina alveolaria), which are located on the maxillary tuber (infratemporal surface) and lead into the alveolar canals.
What else to study on this topic
- Interaction of the maxilla with other bones of the facial skeleton in the formation of the orbit and nasal cavity.
- Anatomy of the palatine bone and formation of the greater palatine canal.
- Variant anatomy of the incisive region (premaxilla) and the incisive suture.
- Topographic relations of the maxillary hiatus and the structures covering it (e.g., the middle nasal concha).
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