Tumors of the Nasal and Paranasal Cavities

Abstract

Embryology and Classification: The lining membrane of the nasal cavity and sinuses is formed from the invaginating ectoderm of the olfactory plates at the end of the fourth week of embryonic life. It is continuous with the mucous membrane of the nasopharynx, which is entodermal in origin but of similar histologic structure. At first these olfactory plates are in contact with the cerebral vessels, but later the meninges and ethmoid bone separate them from the brain. Outgrowths of the nasal lining in the third month form the middle meatus, and further extensions at the posterior end form the pockets for the maxillary sinus. From the anterior portion four furrows develop, two representing buds for the frontal sinuses and the remainder the air cells of the ethmoid. The lining membrane differentiates to form ciliated columnar epithelium resembling the respiratory epithelium of the pulmonary tract. From the undifferentiated cells of the basal layers the mucous glands of Bowman are derived. The submucous tissue of this region is particularly rich in mucous glands and in blood vessels. Portions of the olfactory ectoderm in the upper ethmoidal region are neuro-epithelial in character and form connections with the olfactory bulb. Gangliomas may rarely form from these cells.