Jaarboek no. 89. 2010/2011 - Koninklijke Maatschappij voor ...
Jaarboek no. 89. 2010/2011 - Koninklijke Maatschappij voor ...
Jaarboek no. 89. 2010/2011 - Koninklijke Maatschappij voor ...
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Natuurkundige <strong>voor</strong>drachten I Nieuwe reeks 89<br />
Ontwikkeling van het bouwplan van het hart<br />
88<br />
Figure 2<br />
Simplified scheme of cardiac development. Cardiac development proceeds grossly according to a two-step process.<br />
First the primary myocardium of the linear heart tube is formed that is of <strong>no</strong>dal character. Its phe<strong>no</strong>type is largely<br />
conserved in <strong>no</strong>dal tissues of the formed heart. TBX2 in cooperation with NKX2.5 and other transcriptional repressors<br />
are involved in this process. The atrioventricular bundle (AVB) forms from the primary interventricular ring, which<br />
is initially <strong>no</strong>dal in character as well. The second step is the formation of the working myocardium of the cardiac<br />
chambers in which TBX5 in cooperation with NKX2.5 plays a pivotal role. An intermediate stage is the formation of<br />
so-called ‘trabecular’ myocardium. The slowly proliferating interiorly localized part will form the bundle branches and<br />
their ramifications (BB) of the ventricular conduction system; the highly proliferative exteriorly localized part will form<br />
the compact myocardium.<br />
<strong>no</strong>t imply that from a lineage point of view these<br />
areas remain the same. Thus the linear heart tube<br />
of a mouse after 8 days of development may merely<br />
consist of only the left ventricle and atrioventricular<br />
canal. Interestingly, Tbx2 is expressed in the ‘<strong>no</strong>dal’<br />
myocardium, which is positioned at the smoothwalled<br />
atrial wall in between the sinus and atrial<br />
<strong>no</strong>dal region. It is attractive to speculate that if this<br />
region does <strong>no</strong>t mature sufficiently, <strong>no</strong>dal-like cells<br />
are found, that may display erroneous automaticity.<br />
Het bovenstaande is ontleend aan A.F.M. Moorman en<br />
V.M. Christoffels, Development of the cardiac conduction<br />
system, Novartis Foundation Symposium 250, Vol. 250<br />
(2003), p. 25-33.<br />
Voor nieuwere ontwikkelingen zij verwezen naar<br />
Th. Horsthuis, V.M. Christoffels, R.H. Anderson en<br />
A.F.M. Moorman: Can recent insights into cardiac development<br />
improve our understanding of congenitally malformed<br />
hearts?, Clinical Anatomy 22:4-20 (2009).
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