Anatomy of the python heart

Abstract

The hearts of all snakes and lizards consist of two atria and a single incompletely divided ventricle. In general, the squamate ventricle is subdivided into three chambers: cavum arteriosum (left), cavum venosum (medial) and cavum pulmonale (right). Although a similar division also applies to the heart of pythons, this family of snakes is unique amongst snakes in having intracardiac pressure separation. Here we provide a detailed anatomical description of the cardiac structures that confer this functional division. We measured the masses and volumes of the ventricular chambers, and we describe the gross morphology based on dissections of the heart from 13 ball pythons (Python regius) and one Burmese python (P. molurus). The cavum venosum is much reduced in pythons and constitutes approximately 10% of the cavum arteriosum. We suggest that shunts will always be less than 20%, while other studies conclude up to 50%. The high-pressure cavum arteriosum accounted for approximately 75% of the total ventricular mass, and was twice as dense as the low-pressure cavum pulmonale. The reptile ventricle has a core of spongious myocardium, but the three ventricular septa that separate the pulmonary and systemic chambers--the muscular ridge, the bulbuslamelle and the vertical septum--all had layers of compact myocardium. Pythons, however, have unique pads of connective tissue on the site of pressure separation. Because the hearts of varanid lizards, which also are endowed with pressure separation, share many of these morphological specializations, we propose that intraventricular compact myocardium is an indicator of high-pressure systems and possibly pressure separation.

How the python heart separates pulmonary and systemic blood pressures and blood flows

“…Hopkinson and Pancoast, 1837;Jacquart, 1855;White, 1959;White, 1968;White, 1976;Webb et al, 1971;Farrell et al, 1998;Jensen et al, 2010). The heart consists of two separate atria, where the right atrium receives oxygen-poor blood carried by the systemic veins, while the left atrium receives oxygen-rich blood from the lungs.…”

“…Function of the python heart pulmonary chamber (cavum arteriosum and cavum pulmonale, respectively), with a third shallow chamber, the cavum venosum, situated between the other two. Three different septa are responsible for this division and while all three are found in the ventricle of all squamates and testudines, they are particularly conspicuous and well developed in the heart of pythons and varanid lizards (Greil, 1903;Acolat, 1943;Webb et al, 1971;Webb, 1979;Van Mierop and Kutsche, 1985;Farrell et al, 1998;Jensen et al, 2010). The vertical septum runs from the apex approximately threequarters of the length towards the base of the ventricle, and thereby completely partitions the caudal part of the ventricle into a right and left side.…”

“…All squamate ventricles contain the cavum venosum, but it is uniquely reduced in pythons (Acolat, 1943;Webb et al, 1971;Jensen et al, 2010) and while blood streams necessarily cross there, the volumes that are exchanged between the two blood streams are at all times small compared with the volume of the python ventricle.…”

“…Hopkinson and Pancoast, 1837;Brücke, 1852;Greil, 1903;Acolat, 1943;Webb et al, 1971;Webb, 1979;Van Mierop and Kutsche, 1985;Farrell et al, 1998;Jensen et al, 2010). Although these anatomical descriptions were performed before the ventricular pressure separation had been measured in vivo, it was speculated that the muscular ridge and the vertical septum provided the basis for functional separation of intraventricular blood flows and pressures during cardiac contraction.…”

A modified S10B silicone plastination method for preparation and preservation of scaled reptile specimens

“…Several reptile units have been constituted private or within the veterinary schools due to this increasing demand (17,30). Not only the clinical case reports, but also the research articles focused on reptiles have been significantly increased over the last decade (2,15,18,33,37). Thereby, updated lectures for reptile clinics have being organized in the veterinary education establishments considering these improvements mentioned above (35).…”