Pleural friction rub is caused by which physiological abnormality?

The presence of a pleural friction rub is indeed caused by the inflamed surfaces of the visceral and parietal pleura rubbing together. This symptom typically arises in conditions where the pleura become inflamed or irritated, such as in pleuritis or pneumonia. When the normally smooth surfaces of the pleura, which are lubricated by pleural fluid, become rough due to inflammation, they can create a characteristic sound during respiration as they slide against each other.

This sound is distinctive and can be auscultated as a grating or rubbing noise, which is a key characteristic of a pleural friction rub. The other options do not accurately describe the physiological abnormality linked to this specific sound. Fluid accumulation in the pleural cavity refers to pleural effusion and would likely diminish the ability to hear a friction rub. Similarly, contraction of intercostal muscles pertains to the mechanics of breathing rather than direct involvement with the pleura. Bronchoconstriction affects airflow in the bronchi and would not relate to the phenomenon of a pleural friction rub.