40 or more pulmonary cell types have been identified making the lung by far the most heterogeneous of organs

  • At the level of the terminal respiratory units, the alveoli,
    • relatively simple cellular composition
      • Type I Alveolar Cell
        • major lining cells which present an extremely large surface area to inhaled air and therefore any toxins ar
        • covers some 90% of the gas exchange area
        • very susceptible to injury
      • Type II Alveolar cell
        • Cuboidal.
        • very active metabolically
        • are the source of the majority of the components of the surfactant ,  (together with non-ciliated bronchiolar (Clara) cells)