|MadSci Network: Anatomy|
Hi Lauren -
Phlegm is an accumulation of mucus that you cough up from the lungs. The mucus is secreted within the lungs to keep things moist. It is also used as a 'conveyor belt' to trap dirt particles. Cell beneath the mucus layer (ciliated cells) move it along the connecting passageways of the lungs, ultimately into the trachea - your windpipe. Each day you unknowingly swallow most of this mucus, thus ridding your lungs of the dirt particles. The digestive system doesn't seem to mind, however.
Nick Bourbaki, MadSci Admin
Try the links in the MadSci Library for more information on Anatomy.