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Architecture of atrial musculature in humans
1Department of Paediatrics, National Heart and Lung Institute, London.
Insights
This study reveals the distinct arrangement of atrial muscular bundles in human hearts, explaining how this structure facilitates atrial contraction and electrical signal conduction.
Area of Science:
- Cardiovascular Anatomy
- Cardiac Electrophysiology
- Heart Musculature
Background:
- The precise arrangement of atrial musculature is crucial for effective cardiac function.
- Understanding atrial muscle architecture aids in explaining cardiac electrophysiology and contraction patterns.
Purpose of the Study:
- To investigate the gross anatomical arrangement of principal muscular bundles in the human atria.
- To elucidate the contribution of this arrangement to atrial contraction and the spread of electrical excitation.
Main Methods:
- Prospective anatomical analysis of 9 normal adult human hearts.
- Detailed dissection of atrial muscles with macrophotography.
Main Results:
- Atrial walls comprise circumferential and longitudinal muscular bundles; right atrial muscles are larger than left.
- Right atrium features terminal crest and pectinate muscles; left atrium has interatrial band and septoatrial bundle.
- Atrial musculature arrangement explains atrioventricular ring movement, atrial contraction, and preferential conduction.
Conclusions:
- The anatomical features of atrial musculature provide a clear explanation for atrial contraction mechanisms.
- The described musculature supports preferential conduction pathways within the atria.
Objective:
To investigate the gross arrangement of the principal muscular bundles of the two atria, and to suggest how it may contribute to contraction and spread of atrial excitation.
Design:
A prospective analysis based on anatomical examination of adult human hearts.
Setting:
A national heart and lung institute and a tertiary referral centre for cardiac disease.
Material:
9 normal postmortem human hearts.
Methods:
Dissection of atrial muscles with macrophotography. RESUltS--The atrial walls consist of circumferential and longitudinal muscular bundles, the former being arranged at the base of the atria with the latter predominating in the parietal walls. The muscular bundles in the right atrium are larger than those in the left. The main muscles forming the right atrial wall are the terminal crest and terminal pectinate muscles. The terminal crest, the most obvious muscle, is arranged longitudinally with its pectinate muscles connecting to the musculature of the atrioventricular vestibule. No structure resembling the terminal crest is seen in the left atrium. Instead the left atrial wall is composed of intermingled series of muscles, chief of these being the interatrial band and the septoatrial bundle. The former is arranged circumferentially at the atrial base, while the latter is mainly longitudinal. The wall of the right atrium is not of uniform thickness because of the presence of the terminal crest and its pectinate muscles on its internal surface. By contrast, the left atrial wall is much more uniform and its average thickness is greater than that of the right atrium. The rim of the oval fossa is the most important muscular structure on the septal surface and is formed by the infolded atrial walls. The other principal muscles of the atria attach to it, so that the rim provides mechanical support for overall movement of the atrial walls. Comparison of the gross arrangement of the atrial musculature with earlier echocardiographic measurements showed that this arrangement of the muscle explains movement of the atrioventricular ring and overall atrial contraction, and provides a suitable substrate for preferential conduction.
Conclusion:
The anatomical features of the atrial musculature explain the known facts concerning atrial contraction and preferential conduction.