Mucus

Mucus, a secretion generated by mucus membranes, serves dual roles in maintaining tissue hydration and acting as a defensive filtration barrier for airborne particles. These membranes are found in specific bodily organs, including the nasal passages, mouth, and throat (Journal of Anatomy).

In Traditional Chinese Medicine (TCM), the phenomenon of phlegm can arise from two distinct patterns of disharmony. First, heart vessel obstruction often results from a complex interplay of Qi stagnation and Yang deficiency and manifests as symptoms like a swollen tongue and respiratory difficulties while reclining (Journal of Ethnopharmacology). Second, "Phlegm fire harassing the pericardium" is typically provoked by sustained emotional stressors negatively impacting the heart and pericardium, leading to physiological symptoms via the disturbance of the mind, or "Shen," which TCM posits is housed in the heart (International Journal of Cardiology).