Document Detail

Atrioventricular valves of the mouse: III. Collagenous skeleton and myotendinous junction.
MedLine Citation:
PMID:  8579256     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves. METHODS: The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction. RESULTS: The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone-shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected. CONCLUSIONS: The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagen-muscle junction in the mitral valve is more similar to the structure of a pennate muscle. The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed.
J M Icardo; E Colvee
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Anatomical record     Volume:  243     ISSN:  0003-276X     ISO Abbreviation:  Anat. Rec.     Publication Date:  1995 Nov 
Date Detail:
Created Date:  1996-03-14     Completed Date:  1996-03-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370540     Medline TA:  Anat Rec     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  367-75     Citation Subset:  IM    
Departamento de Anatomía y Bilogía Celular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain.
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MeSH Terms
Chordae Tendineae / ultrastructure*
Microscopy, Electron, Scanning
Mitral Valve / anatomy & histology,  ultrastructure*
Papillary Muscles / ultrastructure*
Specimen Handling / methods
Tricuspid Valve / anatomy & histology,  ultrastructure*
Reg. No./Substance:

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