"Microscopic Anatomy Respiratory System Scott Blystone" GABY Flashcards
Respiratory System Functions
- Conduction of air
- Conditioning of air
- Gas exchange
- Host defense
Inspiration
Active at rest through contraction of external intercostals and diaphragm
Expiration
Passive at rest through the elastic recoil properties of the connective tissue in the lungs and chest wall
Air Conditioning
- Inspired air is filtered to prevent entry of pathogens or irritants
- Inspired air is warmed and humidified to promote gas exchange and to prevent tissue damage due to cold air or desiccation
Gas Exchange
• Highly specialized epithelia
– Maximize surface area
– Minimize diffusion distance
Respiratory Epithelia
• Conducting Portion
– pseudostratified columnar with cilia
• Respiratory Portion (Gas Exchange)
– simple squamous
Respiratory Epithelia
- *Ciliated pseudostratified columnar cells
- *Mucous goblet cells
- *Brush cells (sensory receptors)
- Basal cells (regenerative)
- Granule cells (neuroendocrine)
*extend to apical lumen
Mucociliary elevator
- Coordinatedbeatingof cilia toward exit
- Particlestrappedin mucous floating on aqueous layer
- Cilia deeper into respiratory tract than goblet cells to prevent retrograde flow
Kartagener syndrome
- dynein dysfunction
- no ciliary beating
- respiratory infections
Conducting Portion
• Nasal Cavity • Larynx • Trachea • Bronchi • Bronchioles – Regular – Terminal
Nasal Cavity (Vestibule)
– transition from keratinized to respiratory epithelium
– Sebaceous and sweat glands
– Vibrissae for filtration
Fossae of Nasal Cavity
• Chambers in skull separated by septum
– 3 Conchae, bony projections covered with epithelium
– 3 Meati, spaces between conchae
Nasal Meati and Conchae
• Dense venous plexus – warmth & humidity • Inferior&Middle – ciliated pseudostratified columnar epithlium • Superior – olfactory epithelium
Olfactory epithelium
• 10 sq. cm. Of superior conchae • Supportingcells – microvilli NOT cilia – apical nuclei • Olfactorycells – bipolar neurons, basal nuclei • Basalcells – regenerative, basal
Paranasal Sinus
- Chambers in bones of skull lined with respiratory epithelium
- Connected to nasal cavity via small passages
Larynx
• Connects pharynx and trachea • Epiglottis prevents food entering trachea • Vocal cords permit phonation – Vestibular fold – True vocal cord
Vestibular Fold (false vocal cord)
- Respiratory Epithelium
- Serous glands in lamina propria
- Lie superior to vocal cords
- No dense ligaments
- No skeletal muscle
Vocal Cords
• Phonation – vocal ligament (fibroelastic) – vocalis muscle (skeletal) • Stratified squamous epithelium – abrasion resistance
Laryngeal cartilage
- Thyroid
- Cricoid
- Subject to ossification
Trachea
- 10 cm tube connecting larynx and bronchi
- ciliated pseudostratified columnar epithelium
- Goblet cells, mixed serous and mucous glands
- Limited elastic fibers
- 16-20 incomplete rings of hyaline cartilage connected dorsally by smooth muscle and fibroelastic ligament
Bronchi
• One primary bronchi per side
• 3 lobar bronchi in right lung, 2 in left lung
• Branches of lobar bronchi are small bronchi
• Histologically similar to trachea, however:
• Cartilage is in irregular plates
• Smooth muscle in irregular bands
– postmortem constriction induces folds
Conducting Bronchioles
• Regular and Terminal
• NO cartilage
• Epithelial transition to ciliated simple columnar/cuboidal
• Increase in smooth muscle for ventilation control
• Few goblet cells or glands
• Clara cells take over secretory function
• Regular:
– mostly columnar with folded intima
• Terminal:
– cuboidal with no folding
Respiratory Portion
• Bronchioles – Respiratory • Alveolar – Ducts – Sacs – Alveoli
Respiratory Bronchiole
• Histologically identical to terminal bronchiole
– some cilia remain on cuboidal epithelium
• Outpockets of alveoli in bronchiolar walls permits gas exchange
Alveolar Ducts and Sacs
- Air passage completely lined with alveolar openings
- Simple squamous epithelium
- NO cilia or clara cells
- Alveolar Sacs are common space share by multiple alveolar openings
Alveolar Cusps
• At common alveolar openings (sacs, ducts), there are knoblike projects containing innervated smooth muscle for regulation of pulmonary ventilation
Alveolar septum
• Diffusion path for gas (IN) – surfactant – epithelium • (two membranes + cytoplasm) – epithelial basal lamina – endothelial basal lamina • fused as one basement membrane – endothelium • (two membranes + cytoplasm) – red blood cell membrane
Alveolar Cells
• Type II – surfactant source – regenerative • Type I – 8% by number, 97% by surface area • Endothelial • Dust • RBC • Fibroblasts, Mast cells
Alveolar macrophage
- Dust cells
- Found from capillary to alveolar space
- Bone marrow origin, differentiate on site
- Critical to host defense against inspired pathogens or irritants
Acellular alveolar features
• Acellular interstitium – type III collagen, elastic fibers, proteoglycans – critical for pulmonary mechanics • Pores of Kohn – equalize air pressure between alveoli – promotes collateral air circulation
Pulmonary Circulation
• Nutrient (systemic)
– Brings oxygen and nutrients to lung tissue
– Found in submucosa
• Functional (pulmonary)
– Blood from pulmonary artery to be oxygenated
– thin walled, low pressure
– follows bronchial tree
– branches to capillaries at sites of gas exchange
Pulmonary Host Defense
• Acid-Base Balance
– Regulate CO2 , short term pH regulator
• Metabolic
– Pulmonary capillary endothelium
• Inactivate bradykinin, serotonin, acetylcholine, etc
• Convert angiotensin I to angiotensin II
• Immunologic
– Cellular
• vibrissae, muco-ciliary elevator, alveolar macrophages
– Humoral
• BALT (Bronchus-Associated Lymphoid Tissue)
• Immunoglobulins A and E
• Monitor for specific antigens in the respiratory tree
– Mast cells reactive to allergens
Pleura
– serous membrane which encapsulates entire lung
– fusion of parietal and visceral layers at hills
– mesothelial layer
Innervation
– both sympathetic and parasympathetic innervation
– regulation of bronchial dilation (ventilation)
– poorly localized pain responses
