LESSON 22 multiple respiratory

• The nasal vestibule is lined by different types of epithelium: pigmented keratinized squamous epithelium in rostral region, non-keratinized squamous epithelium in middle part, and pseudostratified non-ciliated columnar epithelium in caudal regions.
• The respiratory region of the nasal cavity is lined by a pseudostratified ciliated columnar epithelium. Five types of epithelial cells are identified: basal cells, ciliated epithelial cells, secretory cells (serous and mucous), brush cells, and non-ciliated cells.
• Basal cells are located at the base of the epithelium and can divide and differentiate into other epithelial cells. They have hemidesmosomes attached to the basement membrane.
• Ciliated epithelial cells are columnar cells with multiple cilia and microvilli. They have a nucleus in the basal portion and a supranuclear Golgi complex.
• Secretory cells produce and secrete specific substances. Serous cells contain neutral glycoproteins, while mucous cells synthesize and accumulate mucinogen. Brush cells have synapses with nerve cells and are considered sensory receptors. Non-ciliated cells metabolize toxic substances.
• The lamina propria is a loose vascularized connective tissue with serous glands. In the caudal regions, there is a cavernous stratum with numerous tortuous venous sinuses. Tubulo-acinar seromucous glands produce lysozyme and enzymes to metabolize fat-soluble toxins.
• The olfactory region is lined by a pigmented olfactory epithelium. It occupies the ethmoturbinates and the caudodorsal area of the nasal cavity and septum. Three cell populations exist: basal cells, olfactory neurosensitive cells, and supportive cells.
• Olfactory neurosensitive cells are bipolar neurons with a dendritic bulb containing cilia and vesicles. Axons cross the lamina propria as unmyelinated nerve fibers and form the olfactory nerve.
• Supportive cells are columnar cells with microvilli, a vesicular nucleus, and a well-developed Golgi complex. They have electron-dense pigment-containing granules.
• The olfactory mucosa is made up of loose connective tissue with numerous tubuloacinar seromucous glands (Bowman’s glands). The lamina propria eliminates odorous substances from the cilia of neurosensitive cells.
• The trachea is a tubular organ that connects the larynx and bronchi. It is made up of a mucosa, submucosa, hyaline cartilage, and muscularis (smooth muscle) or adventitia (depending on location).
• The mucosa is lined by a pseudostratified ciliated columnar epithelium, with added club cells and neuroendocrine cells. Club cells are secretory cells that metabolize toxic substances, while neuroendocrine cells are pyramidal-shaped cells that release hormones.
• The submucosa and the lamina propria are made up of vascularized connective tissue with many elastic fibers and abundant tubuloacinar seromucosal glands.
• The trachea has incomplete cartilages made up of hyaline cartilage. The shape is like the letter “U” or “C”, except in birds.

Test your knowledge of the anatomy and physiology of the respiratory system with this quiz. Explore topics such as the structure of the trachea, bronchial tree, and associated muscle fibers.