Changes

==Avian Ventilation==

==Avian Ventilation==

*Ventilation is birds is strikingly different to that of mammals in that air flows through the lungs in the same direction during both inspiration and expiration. In addition, both the intaking of air and the expelling of air are active processes, requiring muscle contraction.

*[[Ventilation - Anatomy & Physiology|Ventilation]] in birds is strikingly different to that of mammals in that air flows through the lungs in the same direction during both [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]]. In addition, both the intaking of air and the expelling of air are active processes, requiring [[Muscles - Anatomy & Physiology|muscle]] contraction.

*During Inspiration, the ribs are drawn forwards and the sternum lowered, the Caudal Sacs recieving fresh air.   

*During Inspiration, the [[Ribs and Sternum - Anatomy & Physiology|ribs]] are drawn forwards and the [[Ribs and Sternum - Anatomy & Physiology|sternum]] lowered, the Caudal air sacs receiving fresh air.   

*Simultaneously, the Cranial air sacs recieve air which was inhaled at the previous inhalation which is drawn from the lungs, this air has lost much of it's oxygen content.

*Simultaneously, the Cranial air sacs recieve air which was inhaled at the previous inhalation which is drawn from the lungs, this air has lost much of it's oxygen content.

*During Expiration, the sternum is drawn caudal and dorsal, the air sacs are compressed, air from the caudal sac passes through the lungs, while the air in the Cranial Sac leaves via the trachea.

*During Expiration, the [[Ribs and Sternum - Anatomy & Physiology|sternum]] is drawn caudal and dorsal, the air sacs are compressed, air from the caudal air sac passes through the [[Lungs - Anatomy & Physiology|lungs]], while the air in the cranial air sac leaves via the [[Trachea - Anatomy & Physiology|trachea]].

*Thus oxygenated air passes through the lungs on both inspiration and expiration.

*Thus oxygenated air passes through the lungs on both [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]].

==Avian Gas Exchange==

==Avian Gas Exchange==