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Developmental changes in the myocardial architecture of the chick
1University of Lausanne, Institute of Histology and Embryology, Switzerland. David.Sedmera@ibcm.unil.ch
Insights
The embryonic chick heart develops distinct ventricular trabeculation patterns crucial for its contractile function. This study details myocardial architecture changes from early embryonic stages to hatching.
Area of Science:
- Developmental Biology
- Cardiovascular Research
- Comparative Anatomy
Background:
- Limited research exists on embryonic and fetal myocardial architecture compared to adult hearts.
- Understanding embryonic heart development is crucial for comparative morphology and studying experimental effects.
Purpose of the Study:
- To investigate the development of chick ventricular myocardial architecture throughout the entire incubation period.
- To establish a basis for interspecies comparison of ventricular morphology.
Main Methods:
- Chick hearts (stages 14-46) were perfusion-fixed and sectioned.
- Ventricular myocardial architecture was examined using scanning electron microscopy.
Main Results:
- From stage 18, the heart developed compact and trabeculated myocardium.
- Trabeculae patterns became ventricle-specific from stage 24, initially radial then spiraling.
- Embryonic trabeculae are vital for contractile function, unlike adult hearts.
Conclusions:
- Embryonic ventricular myocardium undergoes significant morphogenesis with changing trabecular patterns.
- The trabecular architecture likely reflects stress directions during embryonic development.
- Trabeculae are essential for embryonic heart contractile function.
Background:
Numerous studies describing myocardial architecture have been performed on the adult heart but considerably fewer have been made during embryonic or fetal development. To serve as a basis for interspecies comparison of ventricular morphology, and as a reference for studying the effects of experimental perturbations, we examined the development of chick throughout the entire incubation period.
Methods:
Chick hearts from stage 14 (day 2) to stage 46 (day 21) were perfusion-fixed, and sectioned in transverse, frontal and sagittal planes. The ventricular myocardial architecture was examined and photographed in the scanning electron microscope.
Results:
At embryonic stage 16 and earlier, the smooth-walled heart loop had an outer myocardial mantle, cardiac jelly, and endocardium. From stage 18, there was an outer compact and inner trabeculated myocardium. Trabeculated myocardium could be subdivided into the outer (basal) portion adjacent to the compact layer and the central (luminal) part. The outer basal layer could be distinguished from the inner luminal by shorter and finer trabeculae with small, round intertrabecular spaces. From stage 24, the patterns of trabeculae and intertrabecular spaces were ventricle-specific. Between stages 24 to 31, abundant trabeculations were present throughout both ventricular cavities. The trabeculae were initially radially arranged, but later adopted a spiral course, which persisted in a simplified form into adulthood.
Conclusions:
The ventricular myocardium undergoes distinctive morphogenesis, characterized by changes in trabecular patterning and orientation. We speculate that the embryonic trabecular architecture reflects the directions of the main stresses. Unlike fetal and adult hearts, which rely mostly on the compact myocardial layer, the trabeculae play a crucial role in the contractile function of the embryonic heart.