Maxilla anatomy: the upper jaw bone, its processes and the maxillary sinus

What it is

The upper jaw bone, paired.

Location

Forms the upper jaw, part of the orbit floor, the hard palate and nasal cavity sides.

Function

Holds the upper teeth and forms the maxillary sinus.

Body system

Skeletal · paired (left and right)

FMA ID

FMA53650 (Foundational Model of Anatomy)

Key facts

• Contains the maxillary sinus, the largest paranasal sinus.
• Its infraorbital foramen transmits the infraorbital nerve.

Clinical relevance

Le Fort fractures involve the maxilla.

The maxillae are a pair of symmetrical bones joined at the midline that form the middle third of the face. Each one forms part of the floor and lateral wall of the nasal cavity, the roof of the mouth, and the lower rim and floor of the orbit. Each contains a maxillary sinus and carries the upper teeth on its alveolar process. (Radiopaedia: Maxilla.)

OpenStax describes the maxilla as one of a pair that together form the upper jaw, much of the hard palate and the medial floor of the orbit. Each upper tooth sits in a deep socket called an alveolus. (OpenStax Anatomy and Physiology 2e, 7.2: The Skull.)

The body is the largest, pyramid-shaped part of the bone. It has four surfaces. The anterior surface carries the canine eminence, the incisive and canine fossae, the infraorbital foramen and, at the midline, the anterior nasal spine. (Radiopaedia: Maxilla.)

The infratemporal surface faces backward and forms the front wall of the infratemporal fossa, and may bear a rounded maxillary tuberosity. The orbital surface is triangular, forms most of the orbital floor and carries the infraorbital groove and canal. The nasal surface has the opening of the maxillary sinus, the nasolacrimal groove and the conchal crest for the inferior nasal concha. (Radiopaedia: Maxilla.)

The infraorbital foramen lies just below the orbital rim and transmits the infraorbital nerve and vessels to the face below the eye. (Kenhub: Maxilla.)

The frontal process rises beside the nose to meet the frontal bone; it helps form the lacrimal fossa for the tear sac. The zygomatic process is a pyramid-shaped projection where three surfaces meet; it joins the zygomatic bone. Chewing forces travel from the teeth to the skull through the frontal and zygomatic processes. (Radiopaedia: Maxilla.)

The alveolar process is the curved lower ridge that holds the upper teeth. Each side has eight sockets, and the canine socket is the deepest. (Radiopaedia: Maxilla.)

The palatine process is a horizontal shelf that grows in from each maxilla. The two shelves join at the midline to form the anterior three-quarters of the hard palate, which is both the roof of the mouth and the floor of the nasal cavity. (OpenStax Anatomy and Physiology 2e, 7.2: The Skull.)

The hard palate is formed by the palatine processes of the maxillae in front and the horizontal plates of the palatine bones behind. Near the front, in the midline behind the central incisors, the incisive canal opens. It carries the nasopalatine nerve and a branch of the descending palatine artery between the nose and the mouth. (TeachMeAnatomy: The Palate.)

The incisive canal runs through the midline of the maxilla, connecting the lower nasal cavity to the upper oral cavity. Its oral opening, the incisive foramen, sits behind the central upper incisors. (Radiopaedia: Incisive canal.)

If the palatal shelves fail to fuse in the midline during development, the result is a cleft palate, with or without a cleft lip. It occurs in roughly 1 in 1,000 births and can cause feeding difficulties, ear infections and speech problems. (TeachMeAnatomy: The Palate.)

The body of the maxilla is hollowed out by the maxillary sinus, the largest paranasal sinus. Its roof is the orbital floor, its floor is the alveolar process, and its back wall faces the pterygopalatine fossa. In a large sinus the roots of the upper molars can project into it. (Radiopaedia: Maxillary sinus.)

The opening of the sinus is high on its medial wall, so it drains poorly, and the maxillary sinus is the one most often involved in sinus infections. For more detail see the paranasal sinuses page. (OpenStax Anatomy and Physiology 2e, 7.2: The Skull.)

Each maxilla joins the frontal, ethmoid, nasal, zygomatic and lacrimal bones, the inferior nasal concha (and part of the middle concha of the ethmoid), the palatine bone, the vomer and the opposite maxilla. (Radiopaedia: Maxilla.)

The maxilla ossifies directly in membrane (intramembranous ossification) from two centres. In a newborn the bone is longer horizontally than it is tall. (Kenhub: Maxilla.)

The maxillary sinus inside the body is already present at birth and keeps developing until about age 14, so the shape of the bone changes through childhood. (Radiopaedia: Maxillary sinus.)

Le Fort fractures are fractures of the midface that separate all or part of it from the skull base. All three types must involve the pterygoid plates of the sphenoid. Le Fort I is a horizontal fracture above the teeth that separates the tooth-bearing part of the maxilla. Le Fort II is pyramidal, with the teeth at its base and the nasofrontal suture at its apex. Le Fort III (craniofacial disjunction) separates the whole face from the skull and has the highest rate of cerebrospinal fluid leak. (Radiopaedia: Le Fort fracture classification.)

Gum disease (periodontitis), often following untreated gingivitis, can resorb the bone of the alveolar process and loosen the upper teeth. (Kenhub: Maxilla.)

The maxilla is the upper jaw and the mandible is the lower jaw. The maxillae are a pair of bones fixed to the rest of the skull, whereas the mandible is a single horseshoe-shaped bone whose rami rise to the temporomandibular joints. The mandible's alveolar border has 16 tooth sockets; the two maxillae together have the same number, eight on each side. (TeachMeAnatomy: The Mandible.)

The mandible moves against the fixed maxillae during chewing. Its head articulates with the temporal bone at the temporomandibular joint, a synovial joint with an articular disc, and the jaw is closed by the temporalis, masseter and medial pterygoid. (TeachMeAnatomy: The Temporomandibular Joint.)

There are other differences. The maxilla is hollow, containing the maxillary sinus, and forms parts of the orbit, nose and palate. The mandible contains no sinus; instead a mandibular canal runs through it, carrying the inferior alveolar nerve and artery to the lower teeth. (TeachMeAnatomy: The Mandible.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Nasolacrimal duct · eye & ear
• Inferior nasal concha · skeletal
• Lacrimal sac · eye & ear
• Tarsal plate of lower eyelid · eye & ear
• Lacrimal bone · skeletal
• Lacrimal canaliculus · eye & ear
• Choroid · eye & ear
• Sclera · eye & ear
• Vitreous body · eye & ear
• Lens · eye & ear