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.
The cholesterol granuloma is a particular form of granulation tissue developing as part of a variety of tissue reactions. It is usually associated with chronic middle ear disease and is common in the mastoid antrum of temporal bone. Cholesterol granuloma is rare in maxillary antrum.
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.
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. The mucous membranes receive their postganglionic parasympathetic nerve innervation for mucous secretion originating from the greater petrosal nerve (a branch of the facial nerve). The superior alveolar (anterior, middle, and posterior) nerves, branches of the maxillary nerve provide sensory innervation.
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.
Retention cysts of maxillary sinus are therapeutic problem for laryngologists and maxillo-facial surgeons. They develop slowly and often without symptoms.