The trachea (Fig. 17-5) -- conducts air to the two main bronchi, which are similar to the trachea histologically. Examine the diagram of trachea and major bronchi.

Examine the longitudinal section of larynx (slide 7), and the slide of trachea (slide 140)  identifying the cartilage of the tracheal rings.

• In the respiratory epithelium, note especially the cilia and the thick basement membrane.

Speculate on the function of the thick basement membrane in respiratory epithelium?

What is the function of the well-developed cilia?

Why do smokers usually find themselves coughing more than non-smokers?

Examine the H&E-stained transverse section of trachea (slide 140) and identify the major layers indicated in Fig. 17-5.

• Note the abundant sero-mucous glands, the ring of cartilage, and the trachealis muscle on the posterior side. Examine the respiratory epithelium carefully.

Why are the trachealis muscle and the shape of the cartilage rings important?

On to the lung.