Histology of Respiratory Tract Flashcards
Classify the epithelium of the nasal cavity
- Pseudostratified, columnar, ciliated epithelium with goblet cells
- Respiratory epithelium
Classify the epithelium of the oropharynx
- Stratified, squamous non-keratinised epithelium
What are the histological features of the pharynx?
- Stratified squamous non-keratinised epithelium
- Lamina propria, with elastic fibres
- Muscularis consisting of skeletal muscle
Classify the epithelium that lines most of the larynx
- Pseudostratified columnar ciliated epithelium with goblet cells
Classify the epithelium of the free edges of the epiglottis, vestibular folds and true vocal cords
- Stratified, non-keratinised squamous epithelium
Why does the oropharynx have particular histological features?
- Adaptive to resist mechanical shearing effects of food passing down it
- Rapid regeneration of cells
- Delicate cilia would be destroyed by mechanical shearing
What are the features of the trachea?
- C-rings of hyaline cartilage to prevent collapse
- Trachealis on posterior aspect to allow partial constriction during coughing and food passage down oesophagus
Describe the sub-mucosa of the trachea
- Loose CT
- Tracheal glands- mixed (serous and mucosal) glands
- Blood vessels and ducts
Describe the cartilage and smooth muscle layer of the trachea
- C-shaped hyaline cartilage having perichondrium and chondrocytes
- Ends of cartilage connected by smooth muscles
- Adventitia- fibro-elastic tissue
What is the histology of the bronchus like?
- Same as trachea
Describe the histology of the secondary/lobar bronchus?
- Irregular hyaline cartilage
- Pseudo stratified ciliated columnar
Describe the histology of the tertiary/segmental bronchus
- Columnar epithelium
- Patches of cartilage
What is the difference in histology between tertiary/segmental bronchi and earlier generations?
- Number of goblet cells reduced (epithelium)
- Number of glands reduced in submucosa
- Cartilage is present in irregular plates
Describe the histological layers of a segmental bronchus
- Pseudostratified ciliated columnar epithelium
- Lamina propria
- Smooth muscle cells
- Tunica submucosa (with bronchial glands)
- Hyaline
- Tunica adventitia
What defines a bronchiole structurally?
- When airways reach a diameter of 1mm or less, walls lack of cartilage- called bronchioles
How does the intrapulmonary bronchial tree distinguish from extra pulmonary?
- Reduction from C-rings of hyaline cartilage to plates of hyaline cartilage
- As IP bronchioles become smaller, respiratory epithelium decreases in height to become cuboidal epithelium at terminal bronchioles and similarly, goblet cells become fewer and glands
Describe the lamina propria of small bronchioles
- No glands
- Surrounded by smooth muscle
Describe the histology of terminal bronchioles
- Last generation of conductive airways
- Divide into respiratory bronchioles
- Thinner mucosa
- Simple, cuboidal epithelium
- Few ciliated cells
- Clara cells
- No goblet cells
- Thinner wall (thin smooth muscle and connective tissue)
Describe the wall of terminal bronchioles
- Solid look
- No alveoli
- Simple cuboidal epithelium (Clara and ciliated cells)
Describe the wall of respiratory bronchioles
- Interrupted look (wall associated alveoli)
- Patches of simple cuboidal epithelium (Clara cells)
- Separated by alveoli (simple squamous, type 1 cells)
What are Clara cells?
- Non-ciliated, non-mucous, secretory cells in RE
- Secrete several distinct proteins
What are alveolar ducts?
- Branch off from respiratory bronchioles and connect them to alveolar sacs
- Show interrupted wall with typical smooth muscle cell bundles and scattered elastin fibres
- At distal ends of ducts, bundles disappears, epithelium not low squamous epithelium
What is the main component of alveolar ducts when they branch off from alveolar sacs?
- Type 1 pneumocytes
- Embedded are small capillaries that bulge into alveolar spaces
- T2 pneumocytes secrete surfactant
Describe the histology of the alveolus
- Very thin nature
- Type 1 alveolar cells
- Larger type 2 alveolar cells (with lamellar bodies)
- Dust cells
- Numerous capillaries within inter alveolar septa
By what process do type 2 pneumocytes release surfactant?
- Exocytosis
What is present in an inter alveolar septum?
- Neutrophils within pulmonary capillary in septum
- Rich with elastic fibres
