How does elasticity affect lung compliance?
Two important factors of lung compliance are elastic fibers and surface tension. More elastic fibers in the tissue lead to ease in expandability and, therefore, compliance. Surface tension within the alveoli is decreased by the production of surfactant to prevent collapse.
What affects elastic recoil of lungs?
Two major factors are responsible for the elastic recoil of the lung: (1) lung connective tissue and (2) surface tension related to the air-liquid interface of the alveolar surface.
Do lungs have elastic recoil?
The forces that are responsible for normal resting expiration come from the elastic recoil of the lung and abdominal organs and from surface tension. The lungs contain a substantial amount of elastic tissue, which stretches as the lung expands during inspiration.
Why is elastic recoil increased in restrictive lung disease?
Restrictive diseases are characterized by a decrease in lung volumes, usually due to an increase in alveolar elastic recoil because of an excess of fibrous tissue in the lung. This extra elastic recoil can lead to an increase in FEV1/FVC, and by holding the airways open, a decrease in Raw.
Does elastin increase compliance?
By contrast, in emphysema – where the elastin is degraded – the lungs have increased compliance and are very easy to inflate, but have reduced capacity to recoil. A patient with a lung such as this may have to force their expiration in order to get the air out of their lungs.
Why do lungs tend to recoil?
Lung recoil is able to occur because the connective tissue of the lungs contains elastic fibers and because the film of fluid lining the alveoli has surface tension. Surface tension exists because the oppositely charged ends of water molecules are attracted to each other .
Why is compliance higher during expiration?
During deflation of the lung (expiration limb), lung surface area decreases faster than surfactant can be removed from the liquid lining and the density of surfactant molecules rapidly increases, which decreases surface tension and increases compliance; thus the initial portion of the expiration limb is flat.
What causes elastic recoil?
This phenomenon occurs because of the elastin in the elastic fibers in the connective tissue of the lungs, and because of the surface tension of the film of fluid that lines the alveoli. As water molecules pull together, they also pull on the alveolar walls causing the alveoli to recoil and become smaller.
How does lung recoil aid in respiration?
The lungs are elastic; therefore, when air fills the lungs, the elastic recoil within the tissues of the lung exerts pressure back toward the interior of the lungs and pushes air back out of the lungs. These outward and inward forces compete to inflate and deflate the lung with every breath.
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.
What happens when the lungs recoil?
Upon exhalation, the lungs recoil to force the air out of the lungs, and the intercostal muscles relax, returning the chest wall back to its original position (Figure 2b). The diaphragm also relaxes and moves higher into the thoracic cavity.
What causes an increase in lung compliance?
Increased compliance can be present where there is degeneration of lung tissue. Degenerative lung tissue diseases (eg emphysema) make it harder for the lungs to expand, and harder to exhale as there is less elastic recoil.
Why does the chest wall have outward elastic recoil?
If the lungs were removed from the thoracic cavity, the chest wall would recoil or spring outward and expand to a larger size (Fig. b). To increase or decrease the size (volume) of the chest wall from this resting position requires an alteration of the external or internal pressures acting on it.
What is elastic recoil muscle?
Elastic recoil occurs when you convert energy temporarily stored in tendons and fascia into a free push.