QS Study

The membranes of all the terminal portions of the lungs through which gaseous exchange occurs between the alveolar air & the pulmonary blood are known as ‘respiratory membrane‘.

The membranes through which gases diffuse from the alveoli to the blood in the pulmonary capillaries, or, vice versa is known as a respiratory membrane or, pulmonary membrane. It allows gases to be exchanged between the pulmonary capillaries, or blood vessels, and the respiratory units of the lungs, which consist of bronchioles, alveolar ducts, atria, and alveoli.

The respiratory membrane consists of three layers:

  • alveolar epithelial cell.
  • fused basement membranes of an alveolar epithelial cell and capillary endothelial cell.
  • capillary endothelial cell.

Different layers of respiratory membrane (From within outwards):

(1) A layer of fluid lining the alveolus or surfactant layer.

(2) Alveolar epithelial layer.

(3) The basement membrane of alveolar epithelium.

(4) An interstitial space between alveolar epithelium and capillary membrane.

(5) The basement membrane of the capillary epithelium.

(6) The capillary endothelial layer.