Maxillary sinus

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Maxillary sinus
Outline of bones of face, showing position of air sinuses.
Latin	sinus maxillaris
Gray's	subject #223 999
Artery	infraorbital artery, posterior superior alveolar artery
Nerve	posterior superior alveolar nerve, medial superior alveolar nerve, anterior superior alveolar nerve, and infraorbital nerve
MeSH	Maxillary+Sinus

The maxillary sinus (or Antrum of Highmore) is the largest of the paranasal sinuses, and is pyramidal in shape.

General characteristics

Found in the body of the maxilla, this sinus has three recesses: an alveolar recess pointed inferiorly, bounded by the alveolar process of the maxilla; a zygomatic recess pointed laterally, bounded by the zygomatic bone; and an infraorbital recess pointed superiorly, bounded by the inferior orbital surface of the maxilla. The medial wall is composed primarily of cartilage. The ostia for drainage is located high on the medial wall and opens into the semilunar hiatus of the lateral nasal cavity; because of the position of the ostia, gravity cannot drain the maxillary sinus contents when the head is erect. The sinus is lined with mucoperiosteum, with cilia that beat toward the ostia. The size of the sinuses varies in different skulls, and even on the two sides of the same skull.

The infraorbital canal usually projects into the cavity as a well-marked ridge extending from the roof to the anterior wall; additional ridges are sometimes seen in the posterior wall of the cavity and are caused by the alveolar canals.

Nasal wall/base

Its nasal wall, or base, presents, in the disarticulated bone, a large, irregular aperture, communicating with the nasal cavity.

In the articulated skull this aperture is much reduced in size by the following bones:

• the uncinate process of the ethmoid above,
• the ethmoidal process of the inferior nasal concha below,
• the vertical part of the palatine behind,
• and a small part of the lacrimal above and in front.

The sinus communicates through an opening into the semilunar hiatus on the lateral nasal wall.

Posterior wall

On the posterior wall are the alveolar canals, transmitting the posterior superior alveolar vessels and nerves to the molar teeth.

Floor

The floor is formed by the alveolar process of the maxilla, and, if the sinus is of an average size, is on a level with the floor of the nose; if the sinus is large it reaches below this level.

Projecting into the floor of the antrum are several conical processes, corresponding to the roots of the first and second molar teeth; in some cases the floor is perforated by the fangs of the teeth.

Pathology

Maxillary sinusitis is inflammation of the maxillary sinuses.

Additional images

Illu09 sinuses.jpg Paranasal sinuses	Left maxilla. Nasal surface.	Medial wall of left orbit.	Left orbicularis oculi, seen from behind.
Coronal section of nasal cavities.	The permanent teeth, viewed from the right.	MRI image showing maxillary sinuses.

External links

• SUNY Radiology Headneck:17Maxill
• Cross section at UV skull/x-front
• Norman/Georgetown lesson9 (latnasalwall3, nasalcavitfrontsec)

v • d • e Bones of head and neck: the facial bones of the skull
Maxilla	Surfaces Anterior: fossae (Incisive fossa, Canine fossa) - Infraorbital foramen - Anterior nasal spine Infratemporal: Alveolar canals - Maxillary tuberosity Orbital: Infraorbital groove - Infraorbital canal Nasal: Pterygopalatine canal Processes Zygomatic process Frontal process (Agger nasi, Anterior lacrimal crest) Alveolar process Palatine process (Incisive foramen, Incisive canals, Foramina of Scarpa, Incisive bone, Anterior nasal spine) Other Body of maxilla - Maxillary sinus
Zygomatic	Orbital process (Zygomatico-orbital) - Temporal process (Zygomaticotemporal) - Lateral process (Zygomaticofacial)
Palatine	Fossae Pterygopalatine fossa - Pterygoid fossa Plates Horizontal plate (Posterior nasal spine) - Perpendicular plate (Pterygopalatine canal, Sphenopalatine foramen, Pyramidal process) Processes Orbital - Sphenoidal
Mandible	Body external surface (Symphysis menti, Mental protuberance, Mental foramen) - internal surface (Mental spine, Mylohyoid line, Sublingual fovea, Submandibular fovea) - Alveolar part of mandible Ramus Mylohyoid groove (Mandibular canal, Lingula) - Mandibular foramen - Angle Coronoid process - Mandibular notch - Condyloid process
Minor/ nose	Nasal bone: Internasal suture - Nasal foramina Inferior nasal concha: Ethmoidal process - Maxillary process Vomer: Wing Lacrimal: Posterior lacrimal crest - Lacrimal groove - Lacrimal hamulus

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