Changes

===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