Changes

[[Image:Routeofairthroughrespiratorysystem.jpg|right|thumb|300px|'''Schematic Diagram showing the route air takes through the respiratory system''']]

[[Image:Routeofairthroughrespiratorysystem.jpg|right|thumb|300px|'''Schematic Diagram showing the route air takes through the respiratory system''']]

The trachea bifurcates at the levels of the 4th-6th intercostal space, approximatley halfway between the thoracic inlet and the [[Diaphragm - Anatomy & Physiology|diaphragm]]. dividing into two Principle 'Bronchi', tubes which conduct air into the lungs. These further divide into smaller bronchi and bronchioles.

The trachea bifurcates at the levels of the 4th-6th intercostal space, approximately halfway between the thoracic inlet and the [[Diaphragm - Anatomy & Physiology|diaphragm]]. It divides into two Principle 'Bronchi', tubes which conduct air into the lungs. These further divide into smaller bronchi and bronchioles within the lung tissue.

The initial division after entry to the lung is known as the '''Principle Bronchi''', and this further divides into two ''Lobar Bronchi' for the left lung, and into four ''Lobar Bronchi'' for the right lung.

The initial division after entry to the lung is known as the '''Principle Bronchi''', and this further divides into two ''Lobar Bronchi' for the left lung, and into four ''Lobar Bronchi'' for the right lung.

==Function==

==Function==

*The bronchi and bronchioles are parts of the ''''Conduction Zone'''' of the respiratory system - allowing the passage of air from the external environment into the lungs where gaseous exchange can take place.  

*The bronchi and bronchioles are parts of the ''''Conduction Zone'''' of the respiratory system - allowing the passage of air from the external environment into the lungs where gaseous exchange can take place. The '''Conduction Zone''' is also known as '''dead space''', and no gaseous exchange can take place in this area.

*Some of the Bronchioles have alveoli scattered along their length, and thus form part of the ''''Respiratory Zone'''' - a site for gaseous exchange.

*Some of the Bronchioles have alveoli scattered along their length, and thus form part of the ''''Respiratory Zone'''' - the site for gaseous exchange.

==Histology==

==Histology==