QS Study

Collapsing (recoil) tendency of lungs

Because of elastic tissue (elastin and collagen), the lungs have a strong tendency to collapse and therefore to pull away from the chest wall. This is called the recoil or collapsing tendency of lungs. Elastic recoil is the tendencies of the lungs to recover as people breathe in and out, preventing the lungs from collapsing on exhalation and allowing them to fill on inhalation.

In people who are sick, the elastic recoil may be decreased, putting patients at risk of airway collapse and other difficulties with breathing.

Fig: Recoil Tendency of Lungs

Mechanism

  1. Elastic elements of the lungs are constantly stretched and tend to regain their resting length.
  2. The surface tension of fluid lining the alveoli has a tendency to reduce the size of each alveolus.

Elastic recoil is made potential by highly elastic fibrous cells in the structure of the lungs. These cells can simply stretch to accommodate the lungs as they expand, and compress when the lungs shrink down on exhalation.

Prevention

  1. Surfactant preventing the collapse of the lungs.
  2. Negative intrapleural pressure.
  3. Interdependence of alveoli between adjacent alveoili.
  4. Residual volume.
  5. Size of alveoli: ↑radius of alveoli, ↓collapsing tendency.
  6. Force of inspiration and presence of pores in between two alveoli.

Force of inspiration and presence of pores in between two alveoli.

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