# “upper respiratory tract”
nasal cavity
paranasal sinuses
(cervical trachea)

# physiological division
1. conducting system mucosa lined by elevator
2. transitional system lined by Clara cells
– P450 enzymes detoxify junk
3. exchange system lined by pneumocytes

# blood suppy: bronchial aa.
– collateral circulation
– ischemia/infarction uncommon

# neoplasms
– stratified squamous epithelium
– chondroma/chondrocytoma

[what kind of epithelium is lining the paranasal sinuses?]

type I pneumocytes
– more susceptible to injury; first to be damaged by inhaled toxin
type II pneumocytes
– produce surfactant (prevent collapse, maintain normal morphology)
– important b/c more resistant to injury
– replicate & replace type I pneumocytes

# normal flora @ conductive system
– Mannheimia haemolytica
– Bordetella bronchiseptica
– bronchi etc. are sterile

# defense mechanisms
– Mucociliary escalator
– Goblet cells + pseudostratified ciliated epithelium
– macrophages containing bacteria moved along just like free bacteria; coughed up and/or swallowed
– smokers have only pseudostratified epithelium; only have cough defense
– Pulmonary Alveolar Macrophages
– all aminals
– Pulmonary Intravascular Macrophages
* within luminal alveolar capillaries
– ruminants
– cats
– pigs
– horses
* humans, dogs, and rodents do not have PIMs (rely instead on hepatic and splenic macrophages to remove circulating agents)

# Predisposition to respiratory dz:
– stress, dehydration,
– pulmonary edema
– left-sided heart failure
– uremia
– ammonia
– smelly barns (“husbantry not optimal”)
– irritant

[end on slide 21]


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