Maxillary sinus

Maxillary sinus
Outline of bones of face, showing position of air sinuses.
Details
Artery	infraorbital artery, posterior superior alveolar artery
Nerve	posterior superior alveolar nerve
Identifiers
Latin	sinus maxillaris
MeSH	D008443
TA98	A02.1.12.023
TA2	780
FMA	57715
Anatomical terminology

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, its apex, directed lateralward, is formed by the zygomatic process; its base, directed medialward, by the lateral wall of the nasal cavity.

It is intimately related to the upper teeth, tear duct, and the floor of the orbital cavity.

It is lined with respiratory epithelium and contains air.

Its walls are everywhere exceedingly thin, and correspond to the nasal orbital, anterior, and infratemporal surfaces of the body of the bone.

The size of the cavity 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 with the middle meatus of the nose, generally by two small apertures left between the above-mentioned bones. In the fresh state, usually only one small opening exists, near the upper part of the cavity; the other is closed by mucous membrane.

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

• 
  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.

External links

• Radiology image: Headneck:17Maxill from Radiology Atlas at SUNY Downstate Medical Center (need to enable Java)
• Cross section image: skull/x-front—Plastination Laboratory at the Medical University of Vienna
• lesson9 at The Anatomy Lesson by Wesley Norman (Georgetown University) (latnasalwall3, nasalcavitfrontsec)