Trying to answer the question what is lung surfactants,its composition and action will help us to understand why we do not spend much energy during breathing, especially during exhalation… Are you ready? ok lets go
Lung surfactants are lipoproteins ( a conjugate of a protein and a lipid molecule) that is found on the surface of lungs which induces surface tension and permits efficient penetration and exchange of oxygen and carbon dioxide gases. Remember; when breathing, we inhale large amounts of oxygen in combination with other gases like nitrogen and exhale carbon dioxide in combination with other gases. These surfactants are made from animal lung extract.
Natural lung surfactants are produced by the aveolar cells in the lungs and line mainly the aveoli and small bronchioles. They prevent the aveoli to collapse after taking a long strain during inhalation. okay, take a breath, then exhale, did you notice the stain created when you inhaled?
These natural surfactants are first produced by the fetus so as to prepare them for proper breathing after the gestation period (about 37 week). Hence, in case of a pre-term labour, artificial lung surfactants are administered to the premature infant intrattracheally to prevent the occurence of respiratory distress syndrome
Compositions of Pulmonary surfactants
Surfactant is composed of approximately 90% lipids and 10% proteins. The four surfactant specific proteins are designated surfactant protein A (SP-A), SP-B, SP-C and SP-D. These proteins can be divided into two groups, SP-B and SP-C are two small hydrophobic proteins, while SP-A and SP-D are large hydrophilic proteins. In the subsequent sections, the structure, composition and some general functions of the surfactant components are described. Since SP-D does not appear to possess any activity related to reducing the surface tension, this protein will not be further discussed in the current review. For more information on this protein the reader is referred to other review article