SFP: respiratory tract and lung histology Flashcards
What portions of the lungs are part of the conducting zone?
Bronchi, bronchioles, and terminal bronchioles
What portions of the lungs are part of the respiratory zone?
Respiratory bronchioles, alveolar ducts, and alveoli
What are the necessary characteristics of the conducting zone for normal pulmonary function?
- A wall that can stay patent for airflow
- Surface mucosa that transports foreign substances or debris out of the system
- Mucosa contributing to a moist surface to condition air
What is the mucosa that lines the conducting system?
Respiratory epithelium aka pseudostratified ciliated columnar epithelium
What cells are found in respiratory epithelium?
Ciliated columnar cells, goblet cells, brush cells, granule cells, and basal (stem) cells
What do goblet cells do?
Produce mucin
What is the function of brush cells in respiratory epithelium?
They’re sensory/chemoreceptors; they can sense chemical toxins and trigger various responses
What are the main proteins found in cilia?
Dynein, nexin, and tubulin
What is dynein?
A protein in cilia that allows for movement
What is nexin?
A protein in cilia that limits the sliding/bending caused by dynein
What is tubulin?
The protein that makes up the bulk of cilia
What is the muco-ciliary escalator? What happens if it doesn’t work?
A combination of a layer of mucus floating on top of water that is moved by coordinated cilia. Chronic infections happen if it does not function correctly.
What are 3 factors that can impact the ability of cilia to move mucus along the surface?
- Metaplasia
- Mutations in dynein changing the structure of cilia and causing ciliary dyskinesia
- CTFR gene mutation alters chloride channels and causing thicker mucus (seen in cystic fibrosis)
Describe the histology of the trachea (deep to superficial).
- Mucosa: respiratory epithelium
- Lamina propria with seromucous glands that make watery mucous
- Submucosa: 12 horseshoe cartilages and the trachealis muscle
- Adventitia: perichondrium and connective tissue
Stimulation of ___ causes forceful coughing.
The trachealis muscle
What is the difference between terminal bronchi and bronchioles?
Bronchioles have no cartilage
Describe the histology of bronchi.
- Mucosa: respiratory epithelium with fewer goblet cells
- Lamina propria with seromucous glands
- Cartilage in the form of plates
- Smooth muscle bundles that increase distally as cartilage decreases
Describe the histology of bronchioles.
- Mucosa: more cuboidal but still ciliated
- Lamina propria with no glands
- No cartilage
What differentiates a terminal from a respiratory bronchiole?
The presence of an alveolus
What are club cells?
The stem cells of bronchioles that secrete components of surfactant, lysozyme, secretory components of IgA.
In club cells, what metabolizes irritants?
Smooth ER P450
Where do we find MALT?
In the submucosa of bronchioles
What is a pulmonary lobule?
A functional unit that defines everything served by a single terminal bronchiole
Blood coming to the capillary travels ___, and blood moving away from the capillary travels ___?
Along the bronchial tree; At the periphery
What are type I alveolar cells?
Squamous alveolar cells that make up the majority of alveolar wall. They contain tight junctions and desmosomes, turnover surfactant, and provide a thin barrier that is permeable to gases
What are type II alveolar cells?
Cells interspersed with type I that act as stem cells and produce surfactant to reduce surface tension and prevent alveolar collapse
