So just like water has a high surface tension, this fluid also has a high surface tension. Now, what that means is because the fluid has a high surface tension, when we actually apply pressure, when we breathe inside these alveoli, we actually need to breathe, we need to create a high pressure to expand them, to inflate them because of the high surface tension of our fluid. And that means without any type of detergent, without any type of surfactant, which is basically a detergent inside the alveoli, we have to apply a high pressure to inflate our alveoli found within our lungs. So what the pulmonary surfactant does is it basically decreases the surface tension of the fluid and it makes it much easier for us to actually breathe in and apply a smaller pressure to inflate those balloon like structures, our alveoli. So pulmonary surfactant is a substance that resembles our detergent because it consists of about 90% of phospholipids and it also contains about 10% protein. So that means it contains polar hydrophilic and nonpolar hydrophobic regions.