How does surface tension arise in the alveoli and how does it influence the compliance of the lung?
Compliance depends on the elasticity and surface tension of the lungs. Therefore, surfactant secreted by type II epithelial cells increases lung compliance by reducing the force of surface tension. A low lung compliance means that the lungs are “stiff” and have a higher than normal level of elastic recoil.
How does surface tension affect the lungs?
Increased surface tension increases cohesion within the alveoli, pulling the alveoli closed. The alveolar cells produce a specialized liquid, surfactant, that decreases the surface tension in the airways reducing the amount of energy required to expand the lungs.
What causes increased lung compliance?
High lung compliance is commonly seen in those with obstructive diseases, such of emphysema, in which destruction of the elastic tissue of the lungs from cigarette smoke exposure causes a loss of elastic recoil of the lung.
What causes a decrease in lung compliance?
Common causes of decreased lung compliance are pulmonary fibrosis, pneumonia and pulmonary edema. In an obstructive lung disease, airway obstruction causes an increase in resistance. During normal breathing, the pressure volume relationship is no different from in a normal lung.
Why do alveoli have surface tension?
The alveoli are the tiny air sacs in the lungs where gas exchange happens. And their walls are lined by a thin film of water, which creates a force at their surface called surface tension.
Why are alveoli covered in surfactant?
The main function of surfactant is to lower the surface tension at the air/liquid interface within the alveoli of the lung. This is needed to lower the work of breathing and to prevent alveolar collapse at end-expiration.
Why soap decreases the surface tension of water?
Soap molecules are composed of long chains of carbon and hydrogen atoms. This separates the water molecules from each other. Since the surface tension forces become smaller as the distance between water molecules increases, the intervening soap molecules decrease the surface tension.
Is increased lung compliance good?
High compliance indicates a pliable lung (one with low elastic recoil) and can be thought of as a grocery bag – this is the case often seen in emphysema. Compliance is highest at moderate lung volumes, and much lower at volumes which are very low or very high.
What is airway resistance and lung compliance?
Dynamic Compliance: It is the continuous measurement of pulmonary compliance calculated at each point representing schematic changes during rhythmic breathing. [2] It monitors both elastic and airway resistance. Airway resistance depends on the air viscosity, density, and length, and radius of airways.
What happens when lung compliance decreases?
Low compliance indicates a stiff lung and means extra work is required to bring in a normal volume of air. This occurs as the lungs in this case become fibrotic, lose their distensibility and become stiffer. In a highly compliant lung, as in emphysema, the elastic tissue is damaged by enzymes.
What is a normal lung compliance?
Normal adult lung compliance ranges from 0.1 to 0.4 L/cm H20. Compliance is measured under static conditions; that is, under conditions of no flow, in order to eliminate the factors of resistance from the equation. Using this equation, total compliance of the lung and the chest wall becomes approximately 0.2 L/cm H20.