What does the term sputum refer to?

Sputum refers to the mucus or fluid that is expelled from the respiratory tract, particularly from the lungs, bronchi, and trachea, during coughing. It is a mixture of saliva and mucus that can also contain cells, pathogens, and cellular debris. When patients have respiratory infections or conditions like bronchitis or pneumonia, they may produce sputum that can vary in consistency and color, providing valuable information for medical diagnoses. This is why the correct answer is that sputum is a secretion from the lungs, bronchi, and trachea.

The other options do not accurately describe sputum. Blood expelled from the lungs is known as hemoptysis and is distinct from sputum. Fluid in the pleural cavity, referred to as pleural effusion, involves a different bodily space and does not pertain directly to sputum. Excess mucus in the nasal passages describes a condition affecting the upper respiratory tract, not the lower respiratory tract, where sputum originates.