The Earliest Stages Of Cardiac Development

The morphogenesis of the four-chambered heart is one of the most intricate processes in higher vertebrate embryology, which involves a program of gene expression, differential growth, spatial organization, and cell movement. Since diffusion of nutrients from the surrounding tissues, which nourishes the rapidly growing embryo in its earliest stages, soon becomes insufficient, the embryonic cardiovascular system is the first functioning organ to appear. Thus, a primitive but functioning...

Preface and acknowledgments

Morphogenesis of the embryonic heart in humans and other higher vertebrates is a complex process which involves an intricate program of tissue remodeling. In particular, the process of septation, as a result of which right and left cardiac chambers become separated, continues to fascinate scientists for over a century now. Thanks to the recent advances in molecular biology, especially in immunohisto-chemistry and (whole mount) in situ hybridization, it has become increasingly possible to...

Development and septation of the ventricles and outflow tract

Septomarginal Tract

As mentioned in chapter 2, the ventricles balloon out from the greater curvature of the tubular heart at the end of the looping stage by means of expansive apical growth Harh & Paul, 1975 Steding & Seidl, 1980 Lamers et al., 1992 . As will be discussed in the next chapter, this ballooning is accompanied by the formation of myocardial trabeculation. In between the ventricles a gradually elongating ridge is formed, which is dubbed the (muscular part of the) interventricular septum. Rather...

Looping Of The Heart Tube

Following the formation of the heart tube, two more or less simultaneously occurring processes accompany the formation of the primitive heart tube. Firstly, during neurulation, which commences at stage 9 (19-21 days p.c.), the embryonic disk flexes and folds along both its transverse and longitudinal axes, resulting in head and tail folds and lateral folds. As a results of the head fold, the most anteriorly positioned structures, being the stomatopharyngeal membrane, the septum trans-versum,...

Development And Septation Of The Atria

Septation of the early inter atrial compartment commences with the appearance of the primary atrial septum, the first indication of which is found at stage 12. When seen from the lumenal side of the primary atrial compartment a myocardial protrusion, called the primary interatrial septum appears in the midline of the dorsocranial wall (Figure 3-A). The dorsal rim of the primary interatrial septum is in continuity with the tissue that surrounds the pulmonary pit, which at this stage is also a...

Development Of The Primary Trabeculated And Compact Myocardium

As stated before, the cardiac compartments develop as progressively enlarging balloon-shaped distensions at the outer curvature of the atrial and ventricular loops. In the ventricular region this ballooning is accompanied by the formation of myocardial trabeculae, visible from stage 12 onward, which allows the ventricles to increase in size in the absence of a coronary circulation Van Mierop & Kutsche, 1984 . Moreover, they enhance contractility Challice & Viragh, 1973 and play an...

Ballooning Of The Cardiac Compartments And Subsequent Development

In the looped heart, an inner (lesser) and outer (greater) curvature can be distinguished, which are important landmarks in the view of subsequent developmental events. The looping process itself is accompanied by a certain degree of torsion since fate map studies have indicated that the outer curvature is initially at the ventral side of the straight heart tube De la Cruz 1999 . From stage 11 onward, four progressively enlarging balloon-shaped distensions appear at the outer curvature of the...

Development Of The Sinus Venosus And Its Derivatives

The posterior most part of the heart tube is commonly known as the sinus venosus which receives the venous blood from the right and left side of the embryo. It consists of two horns connected to the rest of the heart tube via the sinu-atrial foramen Steding et al., 1990 . These horns receive blood from the vitelline, umbilical and common cardinal veins. Reconstructions of the venous pole of the heart in mouse embryos, based on molecular expression patterns in the surrounding myocardium, have...

Blood Flow In The Tubular Heart

At stage 11, the heart tube has looped completely and despite the fact that it has lost its left-right symmetry, it can still be considered a homogeneous structure from both morphological and functional points of view. The embryonic cardiomyocytes, derived from the cardiogenic plate mesoderm, form a layer, which is dubbed primary myocardium. Impulse propagation and the subsequent contraction waves, which initially have a peristaltoid form, run from the inflow to the outflow end of the heart...

References

The development of the conducting tissues. In Roberts EA, ed. Cardiac Arrhythmias in the Neonate Infant and Child. New York, NY Appleton-Century-Crofts 1978. Anderson RH, Becker RA. Cardiac anatomy an integrated text and colour atlas. London Gower Medical Publishing, Churchill Livingstone 1980. Anderson RH, Webb S, Brown NA. Clinical anatomy of the atrial septum with reference to its developmental components. Clin Anat 1999 12 362-374. Anderson RH, Brown NA,...