Keywords
endocardial cushions
chordae tendineae
papillary muscles
intrauterine ontogenesis
Abstract
In press
Background. The increasing incidence of Сongenital Heart Defects (CHDs) drives interest in the study of cardiogenesis. Despite the successes of morphological research on the human heart, controversial issues remain. Understanding the precise chronology and dynamics of morphofunctional changes in the human atrioventricular heart valves provides a foundation for the development of prenatal diagnostics and pediatric cardiac surgery.
Aim. To investigate the initiation and formation of atrioventricular valve apparatuses in the human heart.
Materials and Methods. The hearts of 17 embryos, 24 prefetuses, and 40 fetuses were examined. Macroscopic, microscopic, histochemical methods, and 3D reconstruction were utilized. The study was qualitative and descriptive; no statistical analysis was performed. This study is a part of the planned research project of the Department of Histology, Cytology, and Embryology at BSMU "Patterns of Morphogenesis, Structural-Functional Organization and Anatomical Variability of Organs and Structures in Various Body Regions and Systems of Humans and Experimental Animals" (implementation period: 01.2026–12.2030), state registration number 0126U003125.
Research Ethics. The Biomedical Ethics Committee of BSMU (Protocol No.5 of February 19, 2026) found no violations of moral or legal standards during the course of this research work.
Results. It was revealed that the initiation of endocardial cushions, from which the atrioventricular valves are formed, begins at the end of the 4th week of intrauterine development. During the fetal period, the valve leaflets remain immature: they are covered with endothelium and contain interstitial cells. The matrix is represented by an amorphous substance and immature fibers. Chordae tendineae begin to form at the 15th week. The primary chordae tendineae are muscular. Subsequently, they differentiate into mature chordae, dominated by dense, regular connective tissue. Thus, chordae tendineae are classified into two types: muscular and fibro-muscular.
Conclusions. 1. Endocardial cushions are identified at the 4th week of embryogenesis and give rise to the atrioventricular valves. 2. In fetuses, the valve leaflets are covered with endothelium and contain interstitial cells and an extracellular matrix with an amorphous substance and immature fibers. 3. Primary chordae tendineae appear at the 15th week in the form of muscular bands. 4. They undergo remodeling and exhibit dense, regular connective tissue. The cords are classified into muscular and fibro-muscular types.
Keywords: theoretical medicine, endocardial cushions, chordae tendineae, papillary muscles, intrauterine ontogenesis.
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