Snake cardiovascular system — a three-chambered heart along the body
Overview of snake circulation — a three-chambered heart whose subdivided ventricle keeps blood streams apart, a mobile position well down the body, and renal and hepatic portal systems.
General educational reference only — not clinical or veterinary advice. Anatomy varies between individual animals; consult a licensed veterinarian for any health concern.
A three-chambered heart
The snake heart has two atria and a single ventricle. That ventricle is not one open space: a muscular ridge divides it into the cavum arteriosum, cavum venosum and cavum pulmonale, and these partitions together with the timing of contraction keep oxygen-rich and oxygen-poor blood largely separate despite the absence of a complete septum. Blood leaves through the pulmonary artery and through both a left and a right aortic arch, which join behind the heart to form the dorsal aorta.
Position within the body
The heart lies well down the body rather than in a chest, typically within the first quarter to third of the snout-to-vent length, and the position varies between species with different habits. It is held loosely enough within the coelom to be displaced as a large prey item is worked down the esophagus, and it shifts with the animal's posture.
Portal systems and blood
As in other reptiles, venous blood returning from the tail and caudal body can pass through a renal portal system, entering the kidneys before rejoining the general circulation. A hepatic portal vein likewise carries blood from the digestive tract to the liver before it returns to the heart. Reptilian red blood cells are large, oval and nucleated, unlike the round anucleate cells of mammals.
