Maxillary sinus

Maxillary sinus
Outline of bones of face, showing position of air sinuses. Maxillary sinus is shown in blue.
Left maxilla, medial view. Maxillary sinus shown in red.
Details
Artery	infraorbital artery, posterior superior alveolar artery
Nerve	posterior superior alveolar nerve, middle superior alveolar nerve, anterior superior alveolar nerve, and infraorbital nerve
Identifiers
Latin	sinus maxilliaris
MeSH	A04.531.621.578
TA	A06.1.03.002 A02.1.12.023
FMA	57715
Anatomical terminology []

The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose.

It is the largest air sinus in the body. 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 are located high on the medial wall and open 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 (see pathology). The ostium of the maxillary sinus is high up on the medial wall and on average is 2.4 mm in diameter; with a mean volume of about 10 ml. Stand near the person during an extraoral examination to visually inspect and bilaterally palpate the maxillary sinuses.

The sinus is lined with mucoperiosteum, with cilia that beat toward the ostia. This membrane is also referred to as the "Schneiderian Membrane", which is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side. The size of the sinuses varies in different skulls, and even on the two sides of the same skull.