The larynx, seen in the image at the right, is the beginning of the lower respiratory tract and leads into the trachea. It works together with the pharynx, tongue, and lips to allow for speech. The epiglottis closes the larynx, preventing inspired air from entering the esophagus and aspiration of food and liquids into the trachea. The larynx contains vocal folds or true vocal cords and vestibular folds or false vocal cords that produce sounds and resonance, respectively. Both are lined by stratified squamous epithelium and in some areas, respiratory epithelium, with an underlying loose connective tissue containing serous-mucous glands. The vocal folds contain a thick layer of skeletal muscle (vocalis muscle), which allows for movement of the folds to produce sounds.

• Take a look at these samples of larynx, an H&E stained frontal section of larynx and a trichrome stained, longitudinal section of monkey larynx.
• Compare and contrast the features of the vocal folds and vestibular folds in the slides and images below. Note areas within the lining epithelium that change from stratified squamous epithelium to pseudostratified columnar, ciliated epithelium (respiratory epithelium). Identify the vocalis muscle in the vocal folds and serous-mucous glands in the mucosa. Last, note the hyaline cartilage in the walls of the larynx.

Now for the trachea.