Changes

==Avian Trachea==

==Avian Trachea==

The avian [[Trachea - Anatomy & Physiology|trachea]] is composed of tightly stacked [[Bones and Cartilage - Anatomy & Physiology|cartilages]] which are shaped similarly to signet rings. These are complete with no dorsal space as in the mammalian [[Trachea - Anatomy & Physiology|trachea]]. They overlap considerably. The trachea can be palpated on the right side of the neck; it runs alongside the [[Oesophagus - Anatomy & Physiology|oesophagus]]. The trachea is lined with [[Respiratory Epithelium - Anatomy & Physiology|respiratory epithelium]]. The trachea bifurcates into two main [[Bronchi and Bronchioles - Anatomy & Physiology|bronchi]] as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.

The avian [[Trachea - Anatomy & Physiology|trachea]] is composed of tightly stacked [[Cartilage - Anatomy & Physiology|cartilages]] which are shaped similarly to signet rings. These are complete with no dorsal space as in the mammalian [[Trachea - Anatomy & Physiology|trachea]]. They overlap considerably. The trachea can be palpated on the right side of the neck; it runs alongside the [[Oesophagus - Anatomy & Physiology|oesophagus]]. The trachea is lined with [[Respiratory Epithelium - Anatomy & Physiology|respiratory epithelium]]. The trachea bifurcates into two main [[Bronchi and Bronchioles - Anatomy & Physiology|bronchi]] as in mammals. The [[Syrinx - Anatomy & Physiology|syrinx]] is formed by this terminal part of the trachea.

==Avian Lungs==

==Avian Lungs==

==Air Sacs==

==Air Sacs==

Birds lack a [[Diaphragm - Anatomy & Physiology|diaphragm]], and their thoracic and abdominal cavities are continuous. The bird has a number of thin walled, easily distensible '''Air Sacs''' which can extend to approximatley 10x the volume of the [[Lungs - Anatomy & Physiology|lungs]]. These are present within body cavities, and extend into some specific [[Bones and Cartilage - Anatomy & Physiology|bones]], to take the place of [[Bone Marrow - Anatomy & Physiology|bone marrow]]. This has the added function of reducing the weight of the bone, as they are essentially filled with air. The air sacs create unidirectional flow of air to maximise oxygen extraction and reduce heat production during flight.

Birds lack a [[Diaphragm - Anatomy & Physiology|diaphragm]], and their thoracic and abdominal cavities are continuous. The bird has a number of thin walled, easily distensible '''Air Sacs''' which can extend to approximatley 10x the volume of the [[Lungs - Anatomy & Physiology|lungs]]. These are present within body cavities, and extend into some specific [[Bones - Anatomy & Physiology|bones]], to take the place of [[Bone Marrow - Anatomy & Physiology|bone marrow]]. This has the added function of reducing the weight of the bone, as they are essentially filled with air. The air sacs create unidirectional flow of air to maximise oxygen extraction and reduce heat production during flight.

The chicken has 8 air sacs:  

The chicken has 8 air sacs: