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The ethmoid air cells consist of numerous thin-walled cavities in the ethmoidal labyrinth [4] that represent invaginations of the mucous membrane of the nasal wall into the ethmoid bone. [3] They are situated between the superior parts of the nasal cavities and the orbits , and are separated from these cavities by thin bony lamellae.
Two other important views are the Water's view which helps visualise the anterior orbital floor and maxillary sinuses; and the Caldwell view which helps to visualise the frontal and ethmoid sinuses and posterior orbital floor. [3]
The maxillary sinuses, the largest of the paranasal sinuses, are under the eyes, in the maxillary bones (open in the back of the semilunar hiatus of the nose). They are innervated by the maxillary nerve (CN V2). [2] The frontal sinuses, superior to the eyes, in the frontal bone, which forms the hard part of the forehead.
Maxillary sinuses are more radiolucent than orbits. Maxillary sinusitis [2] Differentiating pathology in maxillary sinus. Maxillary sinus shows radiopacity. [2] Mucous membrane shows thickening. [2] Air-fluid level may be observed if the radiograph is taken in "head-up" position. [2] It is not seen in radiograph taken in lying down position.
Grade II is characterized by severe pain for up to 24 h, with some mucosal thickening on X-ray. Patients with grade III have severe pain lasting for more than 24 h and X-ray shows severe mucosal thickening or opacification of the affected sinus; epistaxis or subsequent sinusitis may be observed.
The frontonasal duct may or may not drain into the ethmoidal infundibulum - this is determined by the place of attachment of the uncinate process of the ethmoid bone: if the uncinate process is attached to the lateral nasal wall, the frontonasal duct will open directly into the middle nasal meatus; if otherwise, it will drain into the infundibulum.
Sinuses are mucosa-lined airspaces within the bones of the face and skull. Each opens into the anterior part of the corresponding middle nasal meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the semilunar hiatus in the middle meatus.
With age, the enlarging maxillary sinus may even begin to surround the roots of the maxillary posterior teeth and extend its margins into the body of the zygomatic bone. If the maxillary posterior teeth are lost, the maxillary sinus may expand even more, thinning the bony floor of the alveolar process so that only a thin shell of bone is present.