The work of breathing is described as the total work required to move the chest wall and expand the lungs.

Which of the following factors does not contribute to the work of beathing?

Question

The work of breathing is described as the total work required to move the chest wall and expand the lungs.

Which of the following factors does not contribute to the work of beathing?

BlackTom AI · Accepted Answer

Here’s how to approach the question about which factor does not contribute to the work of breathing.
Option 1: Elastin and collagen fibres. These fibres provide the structural framework and elastic recoil of the lungs and chest wall. While they influence elastic properties, the work of breathing is affected by how much effort is needed to overcome elastic recoil; changes or dysfunction in these fibres can increase or decrease the work required, so this option can be relevant to work of breathing rather than being irrelevant.
Option 2: Alveolar pressure. Alveolar pressure is central to breathing dynamics. The generation and fluctuation of alveolar pressure differences drive air in and out of the lungs, directly determining the work needed to move air and expand the lungs. Therefore, this factor clearly contributes to the work of breathing.
Option 3: Surface tension. Surface tension at the air-liquid interface in the alveoli resists expansion and increases the work required to inflate the lungs, particularly in smaller alveoli where law of Laplace effects are pronounced. Surfactant reduces this work, but surface tension itself is a contributor, so it is indeed involved in the work of breathing.
Option 4: Lung size. While the size of the lungs determines the resting volume and capacity, the question is about the work required to move the chest wall and expand the lungs during breathing. Lung size per se does not directly add a separate mechanical work component; the work is mainly due to elastic recoil, airway resistance, and surface tension. In other words, lung size is more a determinant of resting capacity than a direct contributor to the ongoing work of breathing in the moment of inspiration or expiration.
Thus, among the options, the factor that does not contribute to the work of breathing in the active sense is lung size, whereas elastin and collagen influence elastic properties, alveolar pressure drives airflow, and surface tension affects the energy required to inflate alveoli.

The work of breathing is described as the total work required to move the chest wall and expand the lungs. Which of the following factors does not contribute to the work of beathing?

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