Lung Internal Surface

Structure and Function

Pulmonary system provides the most intimate interface with the external environment .  epresents the largest body surface area exposed to the environment

A coronally reformatted 3D image revealing the bronchial anatomy, from the trachea, (about) 1.6cms mainstem bronchi to the medium sized airways and finally to the small airways (2mm and less). 32679


The surface area of the alveoli is equal to about  1/2 a tennis court.  A tennis court is  78 by 36 feet equal to an area of 2,808 sq feet. Estimates for the surface area for the alveoli  are between  800-1100 sq feet.

The skin in comparison of an adult is approximately 22 square feet

The surface area of the lungs is as large as 1/2 a tennis court which is 78 by 36 feet equal to an area of 2,808 sq feet. (estimates 800-1100 sq feet )


Each day, the lungs are exposed to 7,000 L of air and all it contains.

  • At the level of the alveoli where gas exchange occurs, the biological barrier presents as an extremely attenuated interface composed of the
    • surfactant
    • 1 cell layer thick membranes
      • alveolar lining and its lamina base
      • endothelial lining and its fused basal lamina.
  • Surfactant
    • first line of defense against immunological, biological and non-biological threats
    • thickness
      •  less than 0.1 μm
    • major components are
      • phospholipids – 90%
      • proteins


Cellular Environment

In order to protect this thin surface from the chemical and biological environment, the immune mechanisms at the interface have to be quite sophisticated  There are about  40 different cell types have been described in the lining tissues, bronchial tree and respiratory tissues


Links and References

Scott, J.E The Pulmonary Surfactant: Impact of Tobacco Smoke and Related Compounds on Surfactant and Lung Development
 2004; 2(1): 3–25.