Document Detail


How the python heart separates pulmonary and systemic blood pressures and blood flows.
MedLine Citation:
PMID:  20435810     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The multiple convergent evolution of high systemic blood pressure among terrestrial vertebrates has always been accompanied by lowered pulmonary pressure. In mammals, birds and crocodilians, this cardiac separation of pressures relies on the complete division of the right and left ventricles by a complete ventricular septum. However, the anatomy of the ventricle of most reptiles does not allow for complete anatomical division, but the hearts of pythons and varanid lizards can produce high systemic blood pressure while keeping the pulmonary blood pressure low. It is also known that these two groups of reptiles are characterised by low magnitudes of cardiac shunts. Little, however, is known about the mechanisms that allow for this pressure separation. Here we provide a description of cardiac structures and intracardiac events that have been revealed by ultrasonic measurements and angioscopy. Echocardiography revealed that the atrioventricular valves descend deep into the ventricle during ventricular filling and thereby greatly reduce the communication between the systemic (cavum arteriosum) and pulmonary (cavum pulmonale) ventricular chambers during diastole. Angioscopy and echocardiography showed how the two incomplete septa, the muscular ridge and the bulbuslamelle - ventricular structures common to all squamates - contract against each other in systole and provide functional division of the anatomically subdivided ventricle. Washout shunts are inevitable in the subdivided snake ventricle, but we show that the site of shunting, the cavum venosum, is very small throughout the cardiac cycle. It is concluded that the python ventricle is incapable of the pronounced and variable shunts of other snakes, because of its architecture and valvular mechanics.
Authors:
Bjarke Jensen; Jan M Nielsen; Michael Axelsson; Michael Pedersen; Carl Löfman; Tobias Wang
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  213     ISSN:  1477-9145     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2010 May 
Date Detail:
Created Date:  2010-05-03     Completed Date:  2010-08-02     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1611-7     Citation Subset:  IM    
Affiliation:
Zoophysiology, Department of Biological Sciences, Aarhus University, Building 1131, Universitetsparken 8000, Aarhus, Denmark.
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MeSH Terms
Descriptor/Qualifier:
Animals
Blood Pressure / physiology*
Boidae / physiology*
Coronary Circulation / physiology*
Heart / anatomy & histology,  physiology*
Heart Ventricles
Myocardial Contraction / physiology
Pulmonary Circulation / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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