Pulmonary Surfactant - Surface Tension Magnitude Inside The Lung

Surface Tension Magnitude Inside The Lung

Even though the surface tension can be greatly reduced by pulmonary surfactant, this effect will depend on the surfactant's concentration on the interface. The interface concentration has a saturation limit, which depends on temperature and mixture composition. Because during ventilation there is a variation of the lung surface area, the surfactant's interface concentration is not usually at the level of saturation. The surface increases during inspiration, which consequently opens space for new surfactant molecules to be recruited to the interface. Meanwhile at the expiration the surface area decreases, the layer of surfactant is squeezed, bringing the surfactant molecules closer to each other and further decreasing the surface tension.

SP molecules contribute to increase the surfactant interface adsorption kinetics, when the concentration is below the saturation level. They also make weak bonds with the surfactant molecules at the interface and hold them longer there when the interface is compressed. Therefore, during ventilation, surface tension is usually lower than at equilibrium. Therefore the surface tension varies according to the volume of air in the lungs, which protects them from atelectasis at low volumes and tissue damage at high volume levels.

Surface tension values
Condition Tension (mN/m)
Water at 25°C 70
Pulmonary surfactant in equilibrium at 36°C 25
Healthy lung at 100% of TLC 30
Healthy lung between 40 and 60% of TLC 1~6
Healthy lung below 40% of TLC <1

Read more about this topic:  Pulmonary Surfactant

Famous quotes containing the words surface, tension, magnitude and/or lung:

    I have passed down the river before sunrise on a summer morning, between fields of lilies still shut in sleep; and when, at length, the flakes of sunlight from over the bank fell on the surface of the water, whole fields of white blossoms seemed to flash open before me, as I floated along, like the unfolding of a banner, so sensible is this flower to the influence of the sun’s rays.
    Henry David Thoreau (1817–1862)

    Many people I know in Los Angeles believe that the Sixties ended abruptly on August 9, 1969, ended at the exact moment when word of the murders on Cielo Drive traveled like brushfire through the community, and in a sense this is true. The tension broke that day. The paranoia was fulfilled.
    Joan Didion (b. 1935)

    Constancy has nothing virtuous in itself, independently of the pleasure it confers, and partakes of the temporizing spirit of vice in proportion as it endures tamely moral defects of magnitude in the object of its indiscreet choice.
    Percy Bysshe Shelley (1792–1822)

    Dylan used to sound like a lung cancer victim singing Woody Guthrie. Now he sounds like a Rolling Stone singing Immanuel Kant.
    —Also quoted in Robert Shelton, No Direction Home, ch. 2, “Prophet Without Honor” (1986)