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Evolution and Development of the Atrial Septum.
Bjarke Jensen1, Tobias Wang2, Antoon F M Moorman1
1Department of Medical Biology, Academic Medical Center, University of Amsterdam, The Netherlands.
Anatomical Record (Hoboken, N.J. : 2007)
|October 20, 2018
Summary
Eutherian mammals uniquely form a complete atrial septum using a second septum, unlike other amniotes. This complex process, though prone to errors like probe patency, may support the high metabolic demands of large offspring.
Area of Science:
- Comparative anatomy
- Developmental biology
- Evolutionary biology
Background:
- Complete atrial septation is present in amphibians and all amniotes.
- Eutherian mammals uniquely employ a second septum for full atrial septation.
- Incomplete atrial septal closure (probe patency) is common in humans, suggesting inefficiency.
Purpose of the Study:
- To review the evolution and development of the atrial septum.
- To understand the unique mechanism of atrial septum formation in eutherian mammals.
Main Methods:
- Comparative analysis of atrial septum development across vertebrates.
- Review of embryological and anatomical literature.
Main Results:
- The most primitive atrial septum, seen in lungfish, has a myocardial component and mesenchymal cap.
- Amniotes close the primary foramen using mesenchymal tissues.
- Secondary perforations in the septal myocardium precede foramen closure; these persist in non-eutherian amniotes but form a secondary foramen in eutherians.
Conclusions:
- The eutherian secondary foramen, despite potential for error, may facilitate oxygenated blood flow to the left heart.
- This mechanism could support the energetic demands of large offspring characteristic of eutherian mammals.
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