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What are the conducting airways?
- Tubes that connect outside air with gas exchange membrane in lungs.
- Pathway for air to move.
Important function of Upper Airways.
Parts of the nose?
- Nares: Smallest diameter in upperairway.
- Nasal Septum
- Nasal fossae
Parts of the Pharynx
- Pharynx: Behind nasal cavity and extends to larynx.
- Nasopharynx: Behind nasal cavity down to soft palate
- Oropharynx: Behind oral cavity from soft palate to base of tongue
- Laryngopharynx: Below base of tongue and above larynx
- Cartilaginous cylindrical structure
- Acts as a valve at entrance to trachea (glottis: opening into trachea)
- Containing a vocal cords
- Thryoid cartilage (main cartilage of larynx)
Rima glottidis or glottis. Can open and close. Helps generate pressure to cough.
- Vocal cord edema (croup; stridor)
- Laryngeal reflex( laryngospasm)
- 8-20 ventrally C-shaped cartilages
- From c6 to t5 (behind angle of louis)
- 11cm long in adults
- 1.5-2.5 cm in diameter
- Bifurcation of trachea into right and left bronchi
- right broncus at 20-30 degree from midline
- left broncus at 45-55 degree from midline
- air is 100% saturated and at 37C at this point.
- Contain less than 1mm in diameter
- Contain no cartilage
- Contain bronchial smooth muscle
- Smooth muscle contractions can nearly close the bronchioles (Broncospasm and bronchoconstriction)
Terminal bronchioles branch to form respiratory bronchioles
Conducting Airway histology
- Mucous secreting epithelium lines lumen of airway
- Basement membrane is next
- Lamina propria contains: Smooth muscle, elastic fibers, blood vessels, nerves.
- Epithelium + Lamina propria = Respiratory Mucosa
- Below mucosa
- contain mucous glands (submucosal glands)
- Surrounds cartilaginous airways and blood vessels
- Ends at bronchioles
1. Ciliated epithelial cells
- 2. Mucous blanks
- Two layers of mucus: gel and sol
- 3. Cilia reach into gel layer exert rapid, forward stroke
- pull gel and layer toward pharynx
- 4. Impairment
- Cigarette smoke
Eosinophils - Associated with asthma caused by allergens
Neutrophils - Associated with bacterial infections
Migrate to airways to phagocytize bacteria
Mast cells - On ephithelial surface of airways. mediators of inflammation released from granules
Epithelial chloride channel
- Movement of water into airway lumen
- Mechanism: Chloride
- 1. (Cl-) ion is secrted into airway through Cl- channel
- 2. Sodium (Na+) follows Cl- to maintain electrical neutrally.
- 3. Water follows Na+ into airway lumen, hydrating mucus and faciliating ciliary function.
Alveoli and Capillaries.
- 300 million alveoli in adult lungs:
- 50-100 m2 gas exchange area
- 100 to 300 microns (um) in diameter
- Pulmonary Capillaries:
- in contact with aveolar membrane
- just large enough to follow passage of red blood cells
- faciliatate gas exchange.
Alveolar Capillary Membrane (AC membrane)
- Thin blood air barrier:
- less than 0.5 um thick
- Composed of:
- Alveolar epithelium
- epithelial basement membrane fused with endothelial basement membrane
- capillary endothelium
Type I and Type II Cells
- Type I epithelial cells:
- comprise most of alveolar surface area
- extremely flat
- Type II epithelial cells:
- compact, polygonal shaped
- protrude into alveolar airspace
- contain lamellar bodies
- secrete surfactant.