Changes

The trachea has incomplete cartilaginous rings. The ventral portion is rigid cartilage while the dorsal fourth is membranous. The trachea enters the lung at a level near the base of the heart. Some species of snakes have a unique saccular diverticulum of open tracheal rings that acts for hissing or as a tracheal lung for gas exchange when gastric contents preclude normal pulmonary function.  

The trachea has incomplete cartilaginous rings. The ventral portion is rigid cartilage while the dorsal fourth is membranous. The trachea enters the lung at a level near the base of the heart. Some species of snakes have a unique saccular diverticulum of open tracheal rings that acts for hissing or as a tracheal lung for gas exchange when gastric contents preclude normal pulmonary function.  

==Lungs==

==Lungs==

The lung morphology of snakes is very species-dependent but is obviously elongated. The left lung is always reduced but may vary from 85% of the length of the right lung to being absent. It is relatively well developed in [[Boidae|boids]] but only vestigial in [[Colubridae|colubrids]].  The anterior part of the lung functions in gas exchange. In [[Boidae|boids]] and [[Colubridae|colubrids]], the respiratory portion of the lung lies between the [[Snake Cardiovascular System|heart]] and the cranial [[Snake Digestive System|liver]] whereas in most viperids and elapids it is cranial to the [[Snake Cardiovascular System|heart]].  The posterior part is thin-walled and non-respiratory, mainly functions as an air sac and contains a major portion of the volume of the respiratory tract. In terrestrial snakes this air sac terminates in the intestinal mesentery near the gallbladder while in aquatic species it may reach to the cloaca and is thicker and more muscular.

The lung morphology of snakes is very species-dependent but is obviously elongated. The left lung is always reduced but may vary from 85% of the length of the right lung to being absent. It is relatively well developed in [[Boidae|boids]] but only vestigial in [[Colubridae|colubrids]].  The anterior part of the lung functions in gas exchange. In [[Boidae|boids]] and [[Colubridae|colubrids]], the respiratory portion of the lung lies between the [[Snake Cardiovascular System|heart]] and the cranial [[Snake Digestive System|liver]] whereas in most [[Viperidae|viperids]] and [[Elapidae|elapids]] it is cranial to the [[Snake Cardiovascular System|heart]].  The posterior part is thin-walled and non-respiratory, mainly functions as an air sac and contains a major portion of the volume of the respiratory tract. In terrestrial snakes this air sac terminates in the intestinal mesentery near the gallbladder while in aquatic species it may reach to the [[Cloaca|cloaca]] and is thicker and more muscular.

*Find out more about [[Lizard and Snake Respiration|respiration]] in snakes.

*Find out more about [[Lizard and Snake Respiration|respiration]] in snakes.

[[Category:Snake_Anatomy]]

[[Category:Snake_Anatomy]]