Changes

****Tympany - associated with dysfunction of the pharyngotubal opening resulting from thickening (oedema, inflammation) or obstruction by a mucosal fold (eg: foals)

****Tympany - associated with dysfunction of the pharyngotubal opening resulting from thickening (oedema, inflammation) or obstruction by a mucosal fold (eg: foals)

===Defense mechanisms===

==Defense mechanisms==

**Particle deposition  

*Particle deposition  

**Coiled nature of turbinates promotes turbulent airflow and impaction of large particles >10 μm in diameter onto the nasal mucosa

**Coiled nature of turbinates promotes turbulent airflow and impaction of large particles >10 μm in diameter onto the nasal mucosa

**Mucociliary escalator  

*Mucociliary escalator  

**Cilia on the respiratory epithelium beat in a co-ordinated manner

**Cilia on the respiratory epithelium beat in a co-ordinated manner

**Caudal direction in nasal cavity

***Cilia beat in a caudal direction in nasal cavity

**Cranial direction in trachea and lower airways

***Cilia beat in a cranial direction in trachea and lower airways

**Mucus is swallowed when it reaches the nasopharynx

***Mucus is swallowed when it reaches the nasopharynx

**Constant movement reduces chances that pathogens can adhere to the respiratory epithelium

***Constant movement reduces chances that pathogens can adhere to the respiratory epithelium

**Mucus

**Mucus

**Produced by the goblet cells of the respiratory epithelium and the submucosal glands  

***Produced by the goblet cells of the respiratory epithelium and the submucosal glands with contribution from lacrimal glands draining into the nose

**with contribution from lacrimal glands draining into the nose

***Traps particles for transportation away and subsequent swallowing

**Trap particles for transportation away and subsequent swallowing

***Physical barrier against mucosal damage

**Physical barrier against mucosal damage

***Prevents dessication of the mucosal epithelium

**Prevents dessication of the mucosal epithelium

***Contains antimicrobial substances

**Contains antimicrobial substances

***Immunoglobulin - IgA

**Immunoglobulin - IgA

****IgA produced by mucosal plasma cells

**IgA produced by mucosal plasma cells

****IgA can attach to specific pathogen antigens (viruses, bacteria) trapping them in the mucus for clearance

**IgA can attach to specific pathogen antigens (viruses, bacteria) trapping them in the mucus for clearance

***Lysosyme

**Lysosyme

****Direct action on bacterial cell walls

**Direct action on bacterial cell walls

****Lactoferrin

**Lactoferrin

*****Inhibits bacterial growth as sequesters iron, an essential co-factor for many bacteria

**Inhibits bacterial growth as sequesters iron, an essential co-factor for many bacteria

**Commensal bacteria

**Commensal bacteria

**The normal bacterial flora of the nasal cavity, pharynx, larynx and proximal portion of the trachea compete with potentially pathogenic bacteria and help to prevent their colonisation (competitive exclusion).

***The normal bacterial flora of the nasal cavity, pharynx, larynx and proximal portion of the trachea compete with potentially pathogenic bacteria and help to prevent their colonisation (competitive exclusion).

**The airway environment distal to the mid-portion of the trachea is effectively sterile.   

***The airway environment distal to the mid-portion of the trachea is effectively sterile.   

**Reflexes

**Reflexes

**Sneezing

***Sneezing

**Coughing

***Coughing

•*Pathology of the upper airways

 

==Pathology of the upper airways==

**Developmental abnormalities  

**Developmental abnormalities  

**Palatoschisis

**Palatoschisis