<Ol> <Li> esophagus </Li> <Li> trachea </Li> <Li> tracheal lungs </Li> <Li> rudimentary left lung </Li> <Li> right lung </Li> <Li> heart </Li> <Li> liver </Li> <Li> stomach </Li> <Li> air sac </Li> <Li> gallbladder </Li> <Li> pancreas </Li> <Li> spleen </Li> <Li> intestine </Li> <Li> testicles </Li> <Li> kidneys </Li> </Ol> <Li> rudimentary left lung </Li> <P> The snake's heart is encased in a sac, called the pericardium, located at the bifurcation of the bronchi . The heart is able to move around, however, owing to the lack of a diaphragm . This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus . The spleen is attached to the gall bladder and pancreas and filters the blood . The thymus is located in fatty tissue above the heart and is responsible for the generation of immune cells in the blood . The cardiovascular system of snakes is also unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart . </P> <P> The vestigial left lung is often small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin . In the majority of species, only one lung is functional . This lung contains a vascularized anterior portion and a posterior portion that does not function in gas exchange . This' saccular lung' is used for hydrostatic purposes to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species . Many organs that are paired, such as kidneys or reproductive organs, are staggered within the body, with one located ahead of the other . </P>

Where is the heart located in a snake