maxillary sinus

The maxillary, or maxillary, sinus (sinus maxillaris) is a cavity of the upper jaw. The anterior wall of the sinus is thin in the center, thickening in the peripheral sections. This wall is formed by the part of the upper jaw between the infraorbital margin and the alveolar process. The posterolateral wall corresponds to the tubercle of the upper jaw. The nasolacrimal canal is adjacent to the anterior section of the medial wall of the maxillary sinus, and the ethmoid cells are adjacent to the posterior section. The lower wall of the sinus is formed by the alveolar process of the upper jaw. The upper wall of the sinus is also the lower wall of the orbit. The maxillary sinus opens into the middle nasal passage. The sinus varies in shape and size.