The epiglottis is the superior portion of the larynx that projects upward from the larynx’s anterior wall. It has both a lingual and a laryngeal surface.
A central elastic cartilage of epiglottis forms the framework of the epiglottis. Its lingual mucosa (anterior side) is lined with a stratified squamous nonkeratinized epithelium.
The underlying lamina propria merges with the connective tissue perichondrium of the elastic cartilage of the epiglottis.

TRACHEA
• Wall consists of mucosa, submucosa, hyaline cartilage, and adventitia
• Cartilage C rings keep the trachea open with gaps between rings filled with trachealis muscle
• The lining is a pseudostratified ciliated columnar epithelium with goblet cells
• Submucosa contains seromucous tracheal glands with ducts opening into the trachea lumen

ALVEOLI – are evaginations or outpocketings of the respiratory bronchioles, alveolar ducts, and alveolar sacs, the terminal ends of the alveolar ducts. The alveoli are lined by a layer of thin, simple squamous alveolar cells or pneumocyte type I cells. The adjacent alveoli share a common interalveolar septum or alveolar wall.
The interalveolar septa consist of simple squamous alveolar cells, fine connective tissue fibers and fibroblasts, and numerous capillaries located in the thin interalveolar septa.
The thin interalveolar septa bring the capillaries close to the squamous alveolar cells of the adjacent alveoli.