1. Conductive portion
2. Transitional portion
3. Exchange portion

Nares to Tertiary Bronchioles

(conductive compartments)

1. Nasal cavity
2. Nasopharynx
3. Larynx     
4. Trachea    
5. Bronchi     
6. Bronchioles

1. Olfaction
2. Phonation
3. Humidification
4. Protection
5. Thermoregulation

1. Vestibular region
2. Olfactory region
3. Respiratory region

• Species- variable
• Reflection of integument
• Hairy stratified squamous epithelium

Histological Organization of the

Olfactory Region

1. Non-ciliated pseudostratified columnar epithelium
2. Connective tissue (lamina propria-tunica submucosa)
3. Layer of cartilage or bone

1. Olfactory cells
2. Sustentacular cells
3. Basal cell

1) Protection

2) Humidification

3) Thermoregulation

1. Pseudostratified, ciliated columnar epithelium with goblet cells
2. Vascularized propria-submucosa of loose fibrous connective tissue with seromucous glands, lymphatic tissue, & thin-walled blood vessels
3. Layer of cartilage or bone

• Portion of pharynx above soft palate
• Connects nasal cavity with oropharynx
• Lined with pseudostratified ciliated columnar epithelium

Characteristics of Larynx

• Irregular shaped muscular tube reinforced with cartilage
• Connects pharynx with trachea
• Functions in phonation

1. Hollow tubular organ
2. Tunica mucosa
3. Lamina propria
4. Fibroelastic lamina
5. Tunica submucosa
6. Tracheal cartilage
7. Tunica adventitia/serosa

• Compound tubuloalveolar gland with extensive pulmonary duct system
• Covered with visceral pleura
• Subpleuaral connective tissue encapsulates the lung & is rich in elastic fibers
• Interlobular connective tissue also rich in elastic fibers
• Lung --> lobes --> lobules
• Pigs, cows, & sheep have apparent lobular subdivisions on surface
• Horses & humans have less distinct lobules
• Carnivores do not have lobular subdivisions

• Extrapulmonary bronchi
• Intracpulmonary bronchi
• Bronchioles

1. Low pseudostratified ciliated columnar epithelium with goblet cells
2. Prominant fibroelastic connective tissue
3. Extensive smooth muscle
4. Branched coiled tubuloalveolar mucous glands

• No cartilage components
• Simple cuboidal epithelium
• Clara cells or bronchiolar cells

• Transitional component at initial portion of the lung
• Responsible for gas exchange

• Alveoli

• Alveolar sacs

• Either capillaries or alveolar ducts?

• Non-ciliated columnar cells
• Apical domes project into the lumen
• Numerous electron-dense secretory granules in apical cytoplasms
• Function in providint proteolytic or mucolytic enzymes

• Cuboidal
• Vacuolated cytoplasm
• Synthesize & secrete surfactant
• Occur singly or in groups of 2 or 3

• Dust cells
• Mononuclear phagocytic cells
• First line of lung defense

1. Flattened cytoplasm of the endothelial cell
2. Endothelial basement membrane
3. Septal connective tissue
4. Alveolar basement membrane
5. Flattened cytoplasm of type I alveolar cells

• Thin tissue septum separating adjacent alveoli
• Alveolar pores

• Apertures between neighboring alveoli
• Provide for collateral air circulation
• Prevents alveolar collapse