Pseudostratified columnar epithelium of the trachea (400X)

Take a look at the epithelium and locate a goblet cell. Their name corresponds to their shape, as they resemble a goblet, with their narrow bases and wide apex. The goblet cells produce mucin that binds small particles in the inhaled air thus clensing it like a filter. The mucin layer settles on top of the cilia, which by coordinated movements push the mucus layer towards the pharynx. If the lumps of mucus are large enough, this triggers a cough so that the mucus is spit out instead of being swallowed.

In addition you can see the lamina propira. It consist of fibroblasts, collagen fibers, elastic fibers, some mast cells and lymphocytes.

There are also seromucous glands in this image. These glands secrete secrete mucin that have a lubricating and protective function. Serous cells secrete a slimy secretion that contains enzymes. The secretion empties into th trache via excretory ducts.