How does infection develop in the sinuses?

Updated: Mar 01, 2018
  • Author: Itzhak Brook, MD, MSc; Chief Editor: Michael Stuart Bronze, MD  more...
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The sinuses are normally sterile under physiologic conditions. Secretions produced in the sinuses flow by ciliary action through the ostia and drain into the nasal cavity. In the healthy individual, flow of sinus secretions is always unidirectional (ie, toward the ostia), which prevents back contamination of the sinuses. In most individuals, the maxillary sinus has a single ostium (2.5 mm in diameter, 5 mm2 in cross-sectional area) serving as the only outflow tract for drainage. This slender conduit sits high on the medial wall of the sinus cavity in a nondependent position. Most likely, the edema of the mucosa at these 1- to 3-mm openings becomes congested by some means (eg, allergy, viruses, chemical irritation) that causes obstruction of the outflow tract stasis of secretions with negative pressure, leading to infection by bacteria.

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