Changes

==Avian Lungs==

==Avian Lungs==

Avian [[Lungs - Anatomy & Physiology|lungs]] are relatively compact, with a bird's lungs being approximately 50% as large as the lung of a mammal of a similar size. The lungs are unlobed and do not have the capacity to expand due to the close arrangement between the finite gas exchange structures, i.e.the air capillaries and blood capillaries and scanty connective tissue. The lungs are positioned in the craniodorsal region of the body, and are deeply indented by both the thoracic [[Spinal Column - Anatomy & Physiology#Vertebrae and Joints|vertebrae]] and [[Ribs and Sternum - Anatomy & Physiology|ribs]]. Birds do not have a pleural cavity as the lungs do not expand, thus the membranes are not necessary. One '''primary bronchus''' from the [[Trachea - Anatomy & Physiology|trachea]] enters each lung, narrowing as it travels through, and communicates with the '''abdominal air sac'''. This bronchus gives off branches as it travels through the lung, known as '''secondary bronchi'''. Each of these gives off a further 400-500 '''parabronchi'''. The parabronchichi give rise to '''atria'''. the atria form '''infundibulae''' from which the '''air capillaries''' emerge.  It is in the walls of the latter structures that [[Gas Exchange - Anatomy & Physiology|gaseous exchange]] takes place.

Avian [[Lungs - Anatomy & Physiology|lungs]] are relatively compact, with a bird's lungs being approximately 50% as large as the lung of a mammal of a similar size. The lungs are unlobed and do not have the capacity to expand due to the close arrangement between the finite gas exchange structures, i.e.the air capillaries and blood capillaries and scanty connective tissue. The lungs are positioned in the craniodorsal region of the body, and are deeply indented by both the thoracic [[Spinal Column - Anatomy & Physiology#Vertebrae and Joints|vertebrae]] and [[Ribs and Sternum - Anatomy & Physiology|ribs]]. Birds do not have a pleural cavity as the lungs do not expand, thus the membranes are not necessary. One '''primary bronchus''' from the [[Trachea - Anatomy & Physiology|trachea]] enters each lung, narrowing as it travels through, and communicates with the '''abdominal air sac'''. This bronchus gives off branches as it travels through the lung, known as '''secondary bronchi'''. Each of these gives off a further 400-500 '''parabronchi'''. The parabronchichi give rise to '''atria'''. The atria form '''infundibulae''' from which the '''air capillaries''' emerge.  It is in the walls of the latter structures that [[Gas Exchange - Anatomy & Physiology|gaseous exchange]] takes place.

==Air Sacs==

==Air Sacs==