Metabolism which is essential for the turtles survival as well as diving ability requires oxygen. However, the metabolic process also produces a harmful side effect called carbon dioxide. The respiratory system of a sea turtle is much like that of a normal turtle with the addition of some special features that come in handy when deep sea diving. All turtles have lungs and must take in oxygen from the air. Sea turtles, however, can survive for extended amounts of time before needing to resurface. In addition they often times inflate their lungs to act as floating devices while they bask in the water (Minamikawa, Naito and Uchida 1997).
 

Mouth, Pharynx and Cloaca
Food, water and other nutrients are ingested into two main cavities in most turtles, the mouth and the pharynx. These two cavities are located inside of a turtles skull. However, sea turtles also have the ability to take in oxygen through their cloaca. This special feature is used in extreme situation typically to keep the turtle alive when oxygen levels are low (i.e. deep sea diving, hibernation) (Dawson 2000).

Glottis and Larynx
The glottis of the turtle is a small opening positioned behind the tongue that acts as a barrier between the pharynx and the larynx when swimming underwater, diving or eating. The larynx is connected to the glottis and leads to the trachea. It is considered to be the upper most portion of the respiratory duct.

Trachea and Bronchus tubes
The trachea is a lengthy, hollow tube, which is much like that of a human. Mid-way down the trachea splits into two separate tubes called bronchus tubes (plural: bronchii). Each bronchus then leads into a lung.

Lungs (right and left)
Sea turtle lungs are designed in the exact format as the lungs of a human. The lungs which lie directly underneath of the turtle's carapace (or upper shell portion) are big, sponge like organs which are also typically pink in color. Throughout the lungs the bronchii break into smaller tube like structures called bronchioles. The bronchioles then continue the pattern, decreasing in size until they come to their end in what is called the alveolus (plural: alveoli). The alveoli are small groups of air sacs which is where the actual gas exchange takes place. The oxygen from the air dissolves into the blood and simultaneously the carbon dioxide diffuses out of the blood into the air.

Adaptations
Again the Leatherbak turtles have the most extreme adaptations which help them surpass the other species in their diving ability. Leatherbacks have the ability to adjust the rate of their breathing to help them recover faster after diving and to help them become more efficient in regards to their oxygen supply (Paladino et al. 1996). They also have the ability to store more oxygen than the other species by having more red blood cells and almost twice the typical blood oxygen carrying capacity in the volume of their lungs (Lutcavage et al. 1992).  Other species utilize their ability to reduce the resistance in their airways and the contribution of their muscles to maximize their breathing capabilities (Lutcavage, Lutz and Baier 1989). They also have large oxygen storage capabilities but their supply will only support them for twenty minutes aerobically. However, using anaerobic respiration most sea turtles can last for three hours or more (Lutz and Bentley 1985). Using anaerobic respiration comes with the price of higher levels of CO₂ which Leatherbacks have shown to be able to tolerate much higher levels of and at a higher PH (Paladino et al. 1990). Hemoglobin levels also play a large role in circulation capabilities. Leatherbacks have higher levels of both hemoglobin and myoglobin which allows them to deliver oxygen more quickly throughout their system. Loggerheads have also been documented as having hemoglobin alterations which are a specialized physiological need in regards to diving behavior in sea turtles (Giardina et al 1992).

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