Editing Croup (section)

==Pathophysiology==
The viral infection that causes croup leads to swelling of the [[larynx]], [[Vertebrate trachea|trachea]], and large [[bronchi]]<ref name=PedN09/> due to infiltration of [[white blood cells]] (especially [[histiocytes]], [[lymphocytes]], [[plasma cells]], and [[neutrophils]]).<ref name=Cherry08/> Swelling produces airway obstruction which, when significant, leads to dramatically increased work of breathing and the characteristic turbulent, noisy airflow known as [[stridor]].<ref name=PedN09/>