Respiratory Histology (Dennis) Flashcards
Conducting (upper) parts of the respiratory system
nasal cavities, pharynx, larynx, trachea, bronchi, conducting bronchioles, and terminal bronchioles
Respiratory (lower) parts of the respiratory system
site of gas exchange; respiratory bronchioles, alveolar ducts, and alveoli
Bronchi - epithelium and structural support
Epithelium: respiratory.
Support: prominent smooth muscle with irregular hyaline cartilage plates
Conducting Bronchioles - epithelium and structural support
Epithelium: simple ciliated cuboidal (in larger bronchioles) to columnar/cuboidal (in smaller bronchioles) with few exocrine glands. Increased elastic fibers.
Support: circular layer of smooth muscle, no cartilage, no submucosa
Terminal bronchioles - epithelium and structural support
Epithelium: simple cuboidal, ciliated cells and club cells. Increased elastic fibers.
Support: thin, incomplete circular layer of smooth m, no cartilage, no submucosa
Respiratory bronchioles - epithelium and structural support
Epithelium: simple cuboidal, ciliated cells, club cells, scattered alveoli. Some elastic fibers.
Support: fewer muscle fiber, around alveolar openings
Alveolar ducts and sacs - epithelium and structural support
Epithelium: simple cuboidal btw many alveoli in textbook, but notes say SQUAMOUS.
Support: bands of smooth muscle around alveolar openings
Alveoli - epithelium and structural support
Epithelium: Type I (flat) and Type II (cuboidal/rounded) – pneumocytes.
Support: none, but there is a network of elastic and reticular fibers.
Layers of respiratory epithelium
Ciliated cells
Goblet cells – modified columnar epithelial cells that synthesize and secrete mucus: mucigen granules are released by exocytosis and combine with water; nucleus at the base of goblet cell
Basal cells – mitotically active
Lamina Propria – rich vascularization
Larynx epithelia, mucus glands, and structures
Mucosa: respiratory epithelium with fiber rich lamina propria
Submucosa: loose/areolar CT, few submucosal glands,
Cartilaginous layer: full cartilage rings transition to irregular cartilage plates
Muscularis layer: continuous with larger bronchi, loosely organized in smaller bronchi
Adventitia: moderately dense CT
Trachea epithelia, mucus glands, and structures
Mucosa: respiratory epithelium with fiber rich lamina propria
Submucosa: denser CT than LP, rich in submucosal glands
Cartilaginous layer: C-shaped hyaline cartilage rings, few submucosal glands
Adventitia: Trachealis m. connective tissue that binds trachea to adjacent structure
Blood air barrier
Parietal and Visceral pleura covered in flattened mesothelium, underneath which lie fibrous tissues of collagen and elastin fibers.
Three components separate air and alveoli:
- “Inner” Type I pneumocytes
- “Middle” Fused basal laminae of the pneumocytes (alveolar epithelium and capillary endothelium)
- “Outer” Capillary endothelial cells
Respiratory cells
Type I – creates surface for gas exchange, closely associated with capillaries
Type II – secrete surfactant; precursor for Type I and Type II pneumocytes
Asthma
Inflammation of airways
- Constriction of smooth muscle in bronchioles
- Infiltration of bronchiolar wall by eosinophils, lymphocytes, and mast cells
- Thick bronchiolar epithelium with increased goblet cells and thicker basement membrane
- Sx: dyspnea, wheezing, productive cough
Emphysema
Permanent enlargement of air spaces distal to terminal bronchioles
- Chronic obstruction of airflow due to narrowing of bronchioles
- Destruction of alveolar walls
- Loss of SA reduces gas exchange
- Caused by smoking, dust inhalation, genetic predisposition
- Sx dyspnea, cough, weight loss
