Histology of the Respiratory System Flashcards
List the functions of the respiratory system
- Supplies oxygen, gets rid of carbon dioxide
- Phonation (voice)
- Olfaction (smell)
- Blood pressure control
- Acid-Base Balance
List the functions of the nasal cavity
- Warms air
- Moistens air
- Filters air
- Site for olfaction
(Has turbulent airflow due to conchae)
Describe the epithelium found in the nasal vestibule
Keratinised stratified squamous epithelium
Describe the epithelium that lines the nasal cavity (except for the vestibule and olfactory region)
Respiratory epithelium
- pseudostratified ciliated columnar epithelium with goblet cells
Describe respiratory epithelium
- Pseudostratified ciliated columnar epithelium
- Goblet cells
- Basal Cell
- Club cells
Describe what you would see in a birds eye view of respiratory epithelium
- Majority ciliated cells
- Significant non-ciliated regions (Goblet cells)
What type of epithelium is found in the oropharynx?
Non-keratinised stratified squamous epithelium
What type of epithelium is found in the larynx and trachea?
Respiratory epithelium
What type of epithelium is found on the epiglottis?
The posterior (larynx facing) side:
- Respiratory epithelium
The anterior (tongue) side:
- Stratified squamous epithelium (non-keratinised)
Describe the mechanism by which the nasal cavity gets blocked
(question NOT referring to soft palate erection)
- The venous sinuses of the the lamina propria in the conchae engorge with blood
- Increased mucus production
What type of epithelium is found in the laryngopharynx?
- Stratified squamous epithelium
Describe the lamina propria found under the respiratory epithelium in the nasal cavity
- Under the epithelium
- Band of connective tissue
- Has seromucous glands
- Has thin-walled venous sinuses
- Has a small amounts of bone
Describe the histology the larynx?
The walls of the larynx:
- Cartilage
The muscles of the larynx:
- Respiratory epithelium
Vocal folds & adjacent structures:
- Stratified squamous epithelium
Where on the larynx can you find stratified squamous epithelium?
The vocal folds
and adjacent structures
Describe the rings of cartilage found on the trachea
- 15-20 rings
- Hyaline cartilage
- Not complete circles (Have a small opening, “C” shaped)
- The opening is spanned by fibroelastic tissue and smooth muscle (trachealis muscle)
What fills the gap in the tracheal cartilage rings?
- fibroelastic tissue
- trachealis muscle (smooth muscle)
Describe the layers of tissue found in the trachea
Respiratory epithelium --> Basal lamina --> Lamina propria - (connective tissue and elastic fibres) --> Submucosa - (connective tissue and seromucous glands) --> Cartilage
Name the 2 divisions of the trachea
Name the cartilaginous ridge that separates them
- The primary (main) bronchi
- The carina
Describe the structure of a bronchus
Respiratory epithelium --> Lamina propria --> Muscularis (ring of smooth muscle) --> Submucosa --> Cartilage (interconnected flat plates, rather than "C" shapes)
Describe the cartilage that surrounds bronchi
- Hyaline cartilage
- Irregular plates
- Fully surrounds the bronchial lumen
Describe the changes in abundance of cartilage as you go down the bronchial tree
Trachea:
- Rings of hyaline cartilage
Bronchi:
- Irregular plates of hyaline cartilage
- Get more discontinuous deeped down
Bronchioles:
- No cartilage (none past segmental bronchi)
Describe the lining of a bronchiole
- Epithelium height decreases from columnar to cuboidal as you go down
- Ciliated epithelium
- Initially some goblet cells
What is the name of the smallest bronchioles to lack respiratory function?
Terminal bronchioles
Bronchioles –> Terminal –> Respiratory bronchioles
Name the first part of the respiratory tree to have respiratory function
Respiratory bronchioles
they have alveoli in their walls
Describe the lumen diameter of bronchioles
Less than 1mm
Do bronchioles have cartilage?
No
List what stimulates the smooth muscle of bronchioles to contract
- Parasympathetic stimulation (M3 muscarinic)
- Histamine
- Other factors (doesn’t matter)
Describe the lining of terminal bronchioles
- Cuboidal ciliated epithelium
- Club cells (project above epithelium)
- Have a layer of smooth muscle
Describe the role of Club (Clara) cells
Club cells are non-ciliated
- Produce surfactant (a little)
- Detoxification
- Immune modulation
- Stem cells
Describe respiratory bronchioles
- Ciliated cuboidal epithelium
- Club cells
- Lots of envagination by alvioli
Describe alveolar ducts
- Split off from respiratory bronchioles
- Lined with alveoli and alveolar sacs
Describe alveolar sacs
- Split off of alveolar ducts
- Groupings of alveoli
Describe the lining of alveoli
- Type 1 alveolar cells
- Type 2 alveolar cells
Describe Type 1 alveolar cells (type 1 pneumocytes)
- Simple squamous epithelium
- Lines the alveolar surfaces
- covers about 90% of the alveolar surface
Describe Type 2 alveolar cells (type 2 pneumocytes)
- Polygonal in shape (found at the joins between alveoli)
- Free surface is covered in microvilli
- Produces surfactant (exocytosis of lamellar bodies)
Describe alveolar macrophages (dust cells)
- Free cells
- Phagocytose foreign bodies
- Usually migrate up the respiratory tree (mucociliary escalator) to be swallowed
- But may move to the septal connective tissue
Describe how type 2 pneumocytes coat the alveolar surface in surfactant
- Surfactant in lamellar bodies in the cytoplasm
- Lamellar bodies are exocytosed
- Surfactant released
Describe the blood-air barrier
The tissue between the alveolar lumen and the pulmonary blood vessels that permeate the alveolar septa
- 2 cells thick
- Type 1 pneumocyte –> Basal lamina (shared) –> Endothelium
List the surfactant producing cells
- Type 2 pneumocytes (main)
- Club cells (minor)
List the layers of the air-blood barrier
Type 1 pneumocyte --> Basal lamina --> Endothelial cell
Describe the layers of the visceral pleura
Outer layer (mesothelium): - simple squamous epithelium
Inner layers:
- fibrous connective tissue
- elastic connective tissue
Mesothelium --> Fibrous and elastic connective tissue --> Alveolar wall
Describe the respiratory tree
Trachea --> Primary Bronchi --> Bronchi --> Bronchioles --> Terminal Bronchioles --> Respiratory Bronchioles --> Alveolar ducts --> Alveolar sacs --> Alveoli
