The initiation of contraction in the embryonic chick heart

How does the tubular embryonic heart work? Looking for the physical mechanism generating unidirectional blood flow in the valveless embryonic heart tube

“…Chicken eggs were windowed on incubation day 3 when the embryos had reached the developmental stages 14/15 according to Hamburger and Hamilton (1951). circular muscle layers (Patten and Kramer, 1933). The consequences of technology-based definitions of peristalsis had by far more impact on the perception of the pumping mechanism of the embryonic heart tube.…”

“…Due to this shift in the general perception of peristalsis and as a result of the discovery of the cardiac conduction system, the sequential contractions of the mature heart chambers were rarely characterized as peristaltic motion since the beginning of the 20th century. The pulsations of the valveless embryonic heart tube, on the other hand, were still regarded as propulsive myocardial peristalsis (e.g., Fano and Badano, 1890;Patten and Kramer, 1933;Goss, 1942;Xavier-Neto et al, 2007).…”

“…Visual observations of pulsating embryonic heart tubes show that their pumping action is characterized by the cyclic generation of traveling mechanical waves sweeping from its venous to its arterial end. These traveling waves have traditionally been interpreted as myocardial peristaltic waves (e.g., Fano and Badano, 1890;Patten and Kramer, 1933;Goss, 1942;Xavier-Neto et al, 2007). It was consequently thought that the early embryonic heart might propel fluid like the gut or like a technical peristaltic pump.…”

Expression of sarcomeric myosin in the presumptive myocardium of chicken embryos occurs within six hours of myocyte commitment

“…This mitotically active epithe-0 1992 WILEY-LISS, INC. lium (Manasek, 1968b;Jeter and Cameron, 1971; Thompson et al, 1990) secretes and rests upon a hyaluronate-rich extracellular matrix, termed cardiac jelly (Manasek, 1970b;Manasek et al, 1973;Markwald et al, 1979b), and the presumptive myocytes are linked by junctional complexes and gap junctions (Manasek, 1968a;Hiruma and Hirakow, 1985). The heart begins electrical activity (Hirota et al, 1987), coordinated contractions (Patten and Kramer, 1933;van Mierop, 1967), looping, septation and valve formation while composed of only two epithelial cell populations: myocytes comprising the myocardium and squamous endothelial precursors of the endocardium (Patten and Kramer, 1933;van Mierop, 1967;Manasek, 1970a). Endocardia1 cushions, which form the valves and partitions of the cardiac chambers, arise by an epithelialmesenchymal transformation of endothelial cells at selected regions along the heart tube (Markwald et al, 1975(Markwald et al, , 1977(Markwald et al, , 1979aBernanke and Markwald, 1982).…”

In vivo imaging of the cyclic changes in cross‐sectional shape of the ventricular segment of pulsating embryonic chick hearts at stages 14 to 17: A contribution to the understanding of the ontogenesis of cardiac pumping function

“…Since the time of Albrecht von Haller, the pumping action of the tubular embryonic heart is usually described as the cyclic generation of myocardial peristaltic waves, suggesting that the early embryonic heart might work like a technical peristaltic pump (e.g., Fano and Badano, 1890;Patten and Kramer, 1933;Goss, 1942;XavierNeto et al, 2007). During the past 20 years, however, hemodynamic data have accumulated that seem to cast doubt on this view (Hu and Clark, 1989;Hu et al, 1991;Forouhar et al, 2006;Butcher et al, 2007) and, thereby, show that, at the present time, we have only relatively scant knowledge about the pumping mechanism that generates unidirectional blood flow in the valveless embryonic heart tube.…”