Major divisions of the respiratory system
<strong>Conducting portion</strong>
- nasal cavity
- nasopharynx
- larynx
- trachea
- bronchi
- terminal bronchioles
<strong>Respiratory portion</strong> 
- respiratory bronchioles
- alveolar ducts
- alveoli

Nasal cavities
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<strong>Paired chambers separated by bony/cartilage septum</strong>

<span style="text-decoration:underline;">Each chamber is divided into:</span>
1. vestibule
2. respiratory segment
3. olfactory segment
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Vestibule of nasal cavity
Site of comm w/ ext. environment
<strong>Stratified squamous keratinized</strong> (w/ hairs)

Where does the transition of epithelium occur in the nasal cavity?
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<strong>End of vestibule</strong>

a) Stratified squamous keratinized (w/ hairs)
b) Pseudostratified columnar ciliated (w/ goblet cells)
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What is respiratory epithelium?
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Pseudostratified columnar ciliated epithelium
(w/ goblet cells)

Basal cells give rise to respiratory epithelium
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Respiratory segment of nasal cavity
Lined w/ respiratory epithelium
- underlying LP attached to periosteum
- lateral wall charachterized by chonchae (a.k.a. turbinates)

Function of conchae / turbinates
1. increase surface area
2. cause turbulance
3. warm / moisture air
4. trap particulate in mucus

Lamina propria of the nasal cavity
Very vascular (warms air)
Contains mucus glands w/ serous demilunes
    - demilune cells secrete lysozyme (antibacterial)

Olfactory segment of nasal cavity
Lined by olfactory epithelium (pseudostrat. columnar)
<strong>Has 4 cell types:</strong>
1) Olfactory cells
2) Sustentacular cells
3) Basal cells
4) Brush cells

Olfactory cells (olfactory segment)
Special visceral sensory cells (bipolar neurons / can regenerate)
- Olfactory vesicle (apical surface) w/ non-motile cilia (receptors)
- Axon arise from basal part of cell
- Axons form olfactory n. (CN I)

Sustentacular cells
Mechanical / metabolic support for olfactory sensory cells
(similar role to glial cells)

Basal cells
Mitotic cells
- renew sensory / sustentacular cells in olfactory epithelium

Brush cells
General sensory cells innervated by trigeminal n. (CN V)
Signal touch from olfactory epithelium
(also found in respiratory epithelium)

What are bowman's glands?
Glands w/in olfactory epithelium (wash away olfactory molecules)

Nasopharynx
Posterior to nasal cavity (joins w/ oropharynx)
- lined w/ respiratory epithelium
- posterior wall contains pharyngeal tonsil (adenoids)

Structure / Function of epiglottis
- core of elastic cartilage
- lingual surface (strat. squam.)
- laryngeal surface (pseudostrat. col.)
- LP contains mixed mucous / serous glands

Larynx
Connects pharynx to trachea
<strong>Characterized by laryngeal cartilages </strong>
 - maintain patancy of larynx 
 - major role in vocalization

<question>
False Vocal Folds
(ventricular folds)
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<strong>Upper pair of folds in larynx</strong>
Covered w/ pseudostrat. columnar 
Lots of serous glands w/in LP

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True Vocal Folds
(vocal cords)
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Lower pair of folds in larynx
- Covered w/ strat. squamous 
- Parallel bundles of elastic fibers form vocal ligaments
- Vocalis mm. parallel to ligaments

Vocalis muscles
Skeletal muscles
Lie parallel to vocal ligaments
<strong>Innervation: vagus n. (CN X) </strong>

Tracheal mucosa
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Pseudostrat. ciliated columnar w/ elastic-rich LP
cilia beat in unison upward (move mucus to oropharynx)

Epithelium rests on very thick BM (dense packed collagen) 
LP = loose CT (immune cells, diffuse / nodular lymphatics)
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Cell types within tracheal mucosa
Ciliated cells
Goblet cells
Brush cells (gen. sensory)
Small granule cells (similar to enteroendocrine)
Basal cells (repopulate epithelium)

Cartilaginous layer of trachea
Hyaline cartilage (16-20, c-shaped)
Posteriorly C-shaped cartilage attached by trachealis m. (smooth m.)

Bronchial cartilage
Similar to trachea except rings (not c shaped)
As bronchi enter lungs, rings replaced by plates

Primary bronchi: intrapulmonary or extrapulmonary
Extrapulmonary
(outside the lungs)

Layers of intrapulmonary bronchus
<span style="text-decoration:underline;"><b>Starting from the lumen
</b></span>Respiratory epithelium (some goblet cells)
Smooth muscle
Cartilage plates

Bronchiole components
Larger bronchioles = respiratory epithelium
Distally -&gt; ciliated columnar -&gt; simple cuboidal
Goblet cells found in only largest bronchioles
<strong>Cartilage replaced w/ smooth muscle (w/ some BV)</strong>

Where are clara cells first found? What do they do?
First found in the bronchioles
Secrete CC16

What is the function of CC16
Prevent adjacent bronchiole wall adhesion during <strong><span style="text-decoration:underline;">expiration
</span></strong>(secreted by clara cells)

Smallest conduction part of respiratory tract? What type of epithelium?
Terminal bronchioles
Simple cuboidal epithelium w/ clara cells

Respiratory bronchiole epithelium
Simple cuboidal epithelium
Proximal: Ciliated &amp; Clara cells
Distally: Clara cells predomninate

Where is the first site of gas exchange?
Respiratory bronchioles

Alveoli
Outpouchings of the lumen of respiratory bronchioles
(main site of gas exchange)

Alveolar epithelium
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<strong>Type I pneumocyte:
</strong>Squamous cells (95% of alveolar lining)
Attached to surrounding cells via tight junctions

<strong>Type II pneumocyte:
</strong>Secretory cells (surfactant)
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