The Respiratory Epithelium

  • Michael J. Welsh


The respiratory epithelium forms a continuous layer of cells that separates air from liquid throughout the lung. The integrity and function of the epithelium are a critical requirement for effective gas exchange, the uptake of 02 from the environment and elimination of C02 from the organism. Transfer of gases between the air and the blood requires two anatomical structures: the conducting airways, which distribute the inspired air within the lungs, and the alveoli, which are the site of 02 and C02 diffusion between the gas phase and the pulmonary capillary blood. The epithelia in both regions serve as passive barriers between gas and fluid phases and perform active ion transport functions. In the airways, the epithelium can actively secrete Cl− or absorb Na+; ion transport is an important determinant of the quantity and composition of the respiratory tract fluid, an essential component of mucociliary clearance. In the alveoli, the epithelium actively absorbs Na+; Na+ absorption is a major factor that maintains a fluid-free alveolus. In the fetal lung, the epithelium actively secretes Cl− fluid secretion is a major requirement for normal pulmonary growth and development.


Apical Membrane Basolateral Membrane Fetal Lung Alveolar Epithelium Tracheal Epithelium 


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Copyright information

© Plenum Publishing Corporation 1987

Authors and Affiliations

  • Michael J. Welsh
    • 1
  1. 1.Laboratory of Epithelial Transport and Pulmonary Division, Department of Internal MedicineUniversity of Iowa College of MedicineIowa CityUSA

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