Similarly to most mammals in the Lungs of a crocodile there are alveoli and when crocodile inspires air the Diaphragmaticus, the liver and other organs move towards the tail allowing air to enter the lungs with a vacuum created. This is similar to the role of the diaphragm in humans. The opposite occurs in expiration. However in contrast with mammals crocodiles have a unidirectional airflow in their lungs similar to the avian (bird) respiratory system although crocodiles do not have air sacs where oxygen is stored in birds. Evidence from scientists suggests that the air drawn into the lungs bypasses one of the bronchi entering the other one of the two. The air, still moving in one direction, then flows from the smaller bronchi into the bypassed airway and then out of the lungs, completing a one-way loop. This gas exchange system is much more efficient as it allows more oxygen to be inspired in each breath as it can be stored.
Another special feature of the crocodiles respiratory and circulation system is its heart. Again similar to humans the crocodile has a four-chambered heart and a double circulation system. The first adaptation of a crocodiles heart is that blood of high and low oxygen concentration is mixed as soon as it leaves the heart via a valve called the foramen of panizza placed in between the right and left aorta. This adaptation occurs in order to slow down the metabolism of crocodiles so they don’t have to eat as much and don’t need as much oxygen for respiration.
However the main adaptations are for when catching prey crocodiles often dive for up to 2 hours and therefore have two main adaptations in their heart to save oxygen for respiration.
Firstly they can constrict the pulmonary artery reducing blood flow to the lungs and instead blood is pumped to the rest of the body through the left and right aorta.
Furthermore the heart has a valve between the left and right aorta called the foramen of panizza, which constricts when underwater separating the left and right aorta so blood with high oxygen is pumped around the body but blood with low oxygen content but rich carbon dioxide content goes to the stomach instead of the lungs which can aid digestion due to the high acidic levels needed in the crocodile’s stomach.