Interdependence

Another important factor in maintaining alveolar stability is interdependence. Each alveolus in the lungs is surrounded by other alveoli (see Figure 17.3, panel a) and all of these alveoli are interconnected with each other by connective tissue. Because of these interconnections, any tendency for an alveolus to collapse is opposed by the surrounding alveoli. As the central

Normal airway

Excess mucus production

Inflammation or edema of airway wall

(d) Loss of radial traction

Normal airway

Excess mucus production

Inflammation or edema of airway wall

(d) Loss of radial traction

Figure 17.3 Airway obstruction. (a) Normal, patent airway with radial traction offered to it by surrounding airways. Resistance in this airway is low and air flows through it freely. (b) The airway is obstructed by the presence of excess mucus and airway resistance is increased. Airflow is reduced. (c) Thickening of the airway wall due to inflammation or edema narrows the lumen of the airway. The decrease in airway radius increases airway resistance and decreases airflow. (d) Destruction of surrounding airways results in the loss of interdependence, or radial traction. Without the structural support offered by surrounding airways, the central airway collapses and airflow through it is reduced.

alveolus collapses, it pulls inward on the surrounding alveoli, stretching them and distorting their shape. In response, the distorted alveoli pull back in the opposite direction to regain their normal shape. In other words, they exert radial traction on the central alveolus. As a result, the alveolus is pulled open and collapse is prevented.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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