Pulmonary surfactants

Abstract

General Considerations And Definitions. Pulmonary alveoli of mammals are lined by by a single layer of epithelial cells forming the alveolar wall. The continuity of the cells which rest on a basement membrane, is interrupted occasionally by pores of Kohn. The alveolar wall contains two types of cells: 1) attenuated cells that are extremely thin. These are the TYPE I cells known also known as the Surface Epithelial cells or Membrane Pneumocytes. 2) large round cells. These are known as TYPE H cells or Great Alveolar cells or Granular Pneumocytes. (Figure 1). On one side of the alveolar wall is the interstitium of the alveolar septum containing capillaries, Iymphatics and connective tissue and on the other side between the wall and the alveolar air is the acellular 'Alveolar Lining Layer'. It covers and is somewhat adherent to the alveolar wall. It is a complex mixtures of lipids, proteins and carbohydrates and is termed the 'Surfactant System Of the Lung'. The highly surface active components of this system play an essential role in determining the normal mechanical properties of the lung, as first suggested by VON NEEHGAARD (1929). They are indispensable to normal pulmonary function and may be altered either primarily or secondarily in certain pathological conditions.