Component composition
Except for alveoli, where gas exchange occurs, walls of respiratory passageways have a consistent, layered pattern. These layers are modified, however, for each passageway and thin as passageways approach the alveoli. The layers include an epithelium, a lamina propria which possesses numerous elastic fibers and/or smooth muscle; a supporting layer to maintain patency, and an outer connective tissue layer. 400x
Epithelium >
The epithelium lining most respiratory passageways is pseudostratified columnar with cilia and goblet cells, commonly referred to as respiratory epithelium. A prominent basement membrane is a common feature in many respiratory passageways.
- Cilia
The epithelium lining most respiratory passageways is pseudostratified columnar with cilia and goblet cells, commonly referred to as respiratory epithelium. A prominent basement membrane is a common feature in many respiratory passageways.
- Goblet cells
The epithelium lining most respiratory passageways is pseudostratified columnar with cilia and goblet cells, commonly referred to as respiratory epithelium. A prominent basement membrane is a common feature in many respiratory passageways.
- Basement membrane
The epithelium lining most respiratory passageways is pseudostratified columnar with cilia and goblet cells, commonly referred to as respiratory epithelium. A prominent basement membrane is a common feature in many respiratory passageways.
Lamina propria >
A lamina propria of loose connective tissue is located between the epithelium and the supportive layer. Many blood vessels are located in this layer to aid in temperature regulation of the air.
- Smooth muscle/elastic lamina >
In a respiratory passageway, the lamina propria may possess an interlacing meshwork of smooth muscle or an elastic lamina of longitudinally arranged elastic fibers. This layer is lacking entirely, however, in the nasal cavities, pharynx and larynx.
- Seromucous glands >
The connective tissue layer beneath the smooth muscle and/or elastic lamina (double-headed arrows) frequently contains mixed glands (G). Their secretions moisten the epithelium and, with cilia, form a mucociliary escalator to remove particulate matter and pollutants from inhaled air and transport them upward. These glands decrease in number and eventually disappear as the diameter of the passageways narrows.
Supporting layer >
Cartilage or bone supports the walls of the larger passageways, keeping the lumen open (patent). This supporting layer diminishes and eventually disappears as passageways become smaller in diameter.
Connective tissue >
Another layer of loose connective tissue surrounds the outer surface of the cartilage.
PREVIOUS