Surfactant and its Role in the Upper Respiratory System and Eustachian Tube

Abstract

Surfactant and its Role in the Upper Respiratory System and Eustachian TubeSurfactant research was originally directed toward lung mechanics, however, with growing information on the biology of the surfactant system it has expanded beyond the borders of basic physiology. The research has become interdisciplinary, not only considering aspects of lungs biology relevant for breathing, but also those aspects relevant for airway defence.Surfactant consists mainly of phospholipids that lower the alveolar surface tension to prevent lung collapse at expiration. They also support mechanical elimination of inhaled pathogens by reducing the viscosity of airway mucus. Approximately 8-10% of surfactant is made up of proteins. Among them, specific proteins SP-A and SP-D play a crucial role in the innate defence system. They belong to collectins family and serve as the first step in immune response to inhaled pathogens. In limited extent, SP-B and SP-C are also involved in immunomodulation.Although numerous studies have focused on the physiological function of surfactant in the lower airways, relatively little is known about its role in the upper respiratory system. Identification of lamellar bodies in ciliated epithelium of the upper airways indicates that surfactant may have a role in normal sinonasal function and pathology. Decreased levels of the