Comparative cardiac anatomy of the reptilia. II. A critique of the literature on the Squamata and Rhynchocephalia

Webb, Grahame J. W.; Heatwole, Harold; Bavay, John de

doi:10.1002/jmor.1051420102

Cited by 29 publications

(30 citation statements)

References 27 publications

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“…Detailed anatomical descriptions of the ventricle of Python are, unfortunately, not available, but the structural similarities between varanid lizards and ophidians have been noted numerous times for more than a century (e.g. Jacquart, 1855;Robb, 1965;Webb et al, 1971Webb et al, , 1974Webb, 1979;van Mierop and Kutsche, 1985;Farrell et al, 1998). Thus, as in Varanus, the ventricular wall surrounding the CA of Python molurus is much thicker than the wall surrounding the CP and the CA is extensively trabeculated compared to the CP T.…”

Section: Arterial and Intraventricular Pressures In Anaesthetised Snakesmentioning

confidence: 99%

Ventricular haemodynamics inPython molurus: separation of pulmonary and systemic pressures

Wang

Altimiras

Klein

et al. 2003

Journal of Experimental Biology

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SUMMARYVascular pressure separation by virtue of a two-chambered ventricle evolved independently in mammals and birds from a reptilian ancestor with a single ventricle, and allowed for high systemic perfusion pressure while protecting the lungs from oedema. Within non-crocodilian reptiles, ventricular pressure separation has only been observed in varanid lizards and has been regarded as a unique adaptation to an active predatory life style and high metabolic rate. The systemic and pulmonary sides of the ventricle in Python molurusare well separated by the muscular ridge, and a previous study using in situ perfusion of the heart revealed a remarkable flow separation and showed that the systemic side can sustain higher output pressures than the pulmonary side. Here we extend these observations by showing that systemic blood pressure Psys exceeded pulmonary pressure Ppul almost seven times (75.7±4.2 versus11.6±1.1 cm H2O). The large pressure difference between the systemic and pulmonary circulation persisted when Psys was altered by infusion of sodium nitroprusside or phenylephrine. Intraventricular pressures, measured in anaesthetised snakes, showed an overlap in the pressure profile between the pulmonary side of the ventricle (cavum pulmonale) and the pulmonary artery, while the higher pressure in the systemic side of the ventricle (cavum arteriosum) overlapped with the pressure in the right aortic arch. This verifies that the pressure differences originate within the ventricle, indicating that the large muscular ridge separates the ventricle during cardiac contraction.

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Section: Arterial and Intraventricular Pressures In Anaesthetised Snakesmentioning

confidence: 99%

Ventricular haemodynamics inPython molurus: separation of pulmonary and systemic pressures

Wang

Altimiras

Klein

et al. 2003

Journal of Experimental Biology

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“…The atrio-ventricular valves have received relative little attention (White, 1968;Webb et al, 1971Webb et al, , 1974Young et al, 1993), and comparative information on their anatomy remains scarce. They emerge as double-flap valves from the interatrial septum, covering the left and right atrio-ventricular openings, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, archosaurs (crocodiles and birds) share a four-chambered heart with a complete separation of the ventricular chambers and an anatomy of the systemic and pulmonary outflow tract that differs from the other groups. Comparative aspects of the anatomy of the heart of the major groups of sauropsids have been elaborated in comprehensive publications and a unified anatomical nomenclature has been suggested (Mathur, 1944(Mathur, , 1946Webb et al, 1971Webb et al, , 1974Webb, 1979;Farrell et al, 1998). In this study, I have focused on the functional anatomy of the heart of the ball python, Python regius.…”

Section: Introductionmentioning

confidence: 99%

Functional morphology and patterns of blood flow in the heart of Python regius

Starck¹

2008

Journal of Morphology

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Brightness-modulated ultrasonography, continuous-wave Doppler, and pulsed-wave Doppler-echocardiography were used to analyze the functional morphology of the undisturbed heart of ball pythons. In particular, the action of the muscular ridge and the atrio-ventricular valves are key features to understand how patterns of blood flow emerge from structures directing blood into the various chambers of the heart. A step-by-step image analysis of echocardiographs shows that during ventricular diastole, the atrio-ventricular valves block the interventricular canals so that blood from the right atrium first fills the cavum venosum, and blood from the left atrium fills the cavum arteriosum. During diastole, blood from the cavum venosum crosses the muscular ridge into the cavum pulmonale. During middle to late systole the muscular ridge closes, thus prohibiting further blood flow into the cavum pulmonale. At the same time, the atrio-ventricular valves open the interventricular canal and allow blood from the cavum arteriosum to flow into the cavum venosum. In the late phase of ventricular systole, all blood from the cavum pulmonale is pressed into the pulmonary trunk; all blood from the cavum venosum is pressed into both aortas. Quantitative measures of blood flow volume showed that resting snakes bypass the pulmonary circulation and shunt about twice the blood volume into the systemic circulation as into the pulmonary circulation. When digesting, the oxygen demand of snakes increased tremendously. This is associated with shunting more blood into the pulmonary circulation. The results of this study allow the presentation of a detailed functional model of the python heart. They are also the basis for a functional hypothesis of how shunting is achieved. Further, it was shown that shunting is an active regulation process in response to changing demands of the organism (here, oxygen demand). Finally, the results of this study support earlier reports about a dual pressure circulation in Python regius.

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“…or cavum pulmonale, by an incomplete horizontal septum, also called muscular ridge, Muskelleiste, or interventricular septum (Greil, 1903;Goodrich, 1919Goodrich, ,1930Leene and Vorstmann, 1930;Kashyap, 1959;Guibé, 1970;Webb et al, 1974;Holmes, 1975;Webb, 1979;Kutsche, 1981,1985). In several species a variably developed vertical septum usually subdivides the cavum dorsale into the cavum venosum and cavum arteriosum.…”

Section: Resultsmentioning

confidence: 97%

Formation of cartilage in the heart of the Spanish terrapin, Mauremys leprosa (Reptilia, Chelonia)

López

Durán

Andrés

et al. 2003

Journal of Morphology

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Cartilaginous deposits are regularly present in the heart of several reptilian, avian, and mammalian species. The formation of these extraskeletal cartilages has been studied in birds and mammals, but not in reptiles. The aim here was to elucidate this question in the Spanish terrapin. Hearts from 23 embryos belonging to Yntema (1968) developmental stages 17 to 26 and eight terrapins age 3 months to 10 years were examined using histological, histochemical, and immunohistochemical techniques. In the heart of the Spanish terrapin (Mauremys leprosa), chondrogenesis can start during embryonic life. Cartilaginous tissue develops from a mesenchymal cellular condensation that extends along the aorticopulmonary septum and the incipient pars fibrosa of the ventricular horizontal septum. This cellular condensation, which is smooth muscle alpha-actin (SMalpha-actin)-negative and type II collagen-negative during stages 17 to 22, acts as a prechondrogenic condensation. In stage 23, production of type II collagen begins in the central core of the condensation and gradually spreads toward its periphery. The type II collagen-positive (chondrogenic) cellular condensation remains devoid of perichondrium prior to birth. Thereafter, it converts into hyaline cartilage that extends along the proximal part of the aorticopulmonary septum and the pars fibrosa of the horizontal septum. Our findings are consistent with the assumption that, as in birds and mammals, the precursors of the cardiac chondrocytes in chelonians are neural crest-derived cells of nonmuscular nature. In addition, they point to the possibility that cells from the neural crest populate the embryonic pars fibrosa of the horizontal septum, thereby contributing to its alignment with the aorticopulmonary septum. In the present species, a second cartilaginous deposit of a hyaline nature extends along the sinus wall of the right semilunar valve of the right aorta, penetrating the fibrous cushion that constitutes the proximal support of the corresponding valve leaflet. This cartilage develops after birth, between the third and eighteenth month of life; its morphogenetic origin is unclear. The cartilaginous foci occurring in hearts of Spanish terrapin appear to act as pivots resisting mechanical tensions generated during the cardiac cycle. In the specimens examined there was no sign of replacement of the cardiac cartilages by bone tissue.

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Comparative cardiac anatomy of the reptilia. II. A critique of the literature on the Squamata and Rhynchocephalia

Cited by 29 publications

References 27 publications

Ventricular haemodynamics inPython molurus: separation of pulmonary and systemic pressures

Ventricular haemodynamics inPython molurus: separation of pulmonary and systemic pressures

Functional morphology and patterns of blood flow in the heart of Python regius

Formation of cartilage in the heart of the Spanish terrapin, Mauremys leprosa (Reptilia, Chelonia)

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