Septation and valvar formation in the outflow tract of the embryonic chick heart

There is no agreement, in the chick, about the number of the endocardial cushions within the outflow tract or their pattern of fusion. Also, little is known of their relative contributions to the formation of the arterial valves, the subpulmonary infundibulum, and the arterial valvar sinuses. As the chick heart is an important model for studying septation of the outflow tract, our objective was to clarify these issues. Normal septation of the outflow tract was studied in a series of 60 staged chick hearts, by using stained whole‐mount preparations, serial sections, and scanning electron microscopy. A further six hearts were examined subsequent to hatching. At stage 21, two pairs of endocardial cushions were seen within the developing outflow tract. One pair was positioned proximally, with the other pair located distally. By stage 25, a third distal cushion had developed. This finding was before the appearance of two further, intercalated, endocardial cushions, also distally positioned, which were first seen at stage 29. In the arterial segment, the aortic and pulmonary channels were separated by the structure known as the aortopulmonary septum. The dorsal limb of this septum penetrated the distal dorsal cushion, whereas the ventral limb grew between the remaining two distal cushions, both of which were positioned ventrally. The three distal endocardial cushions, and the two intercalated endocardial cushions, contributed to the formation of the leaflets and sinuses of the arterial roots. The two proximal cushions gave rise to a transient septum, which later became transformed into the muscular component of the subpulmonary infundibulum. Concomitant with these changes, an extracardiac tissue plane was formed which separated this newly formed structure from the sinuses of the aortic root. Our study confirms that three endocardial cushions are positioned distally, and two proximally, within the developing outflow tract of the chick. The pattern of the distal cushions, and the position of the ventral limb of the aortopulmonary septum, differs significantly from that seen in mammals. Anat Rec 264:273–283, 2001. © 2001 Wiley‐Liss, Inc.

[1]  A. McMahon,et al.  Fate of the mammalian cardiac neural crest. , 2000, Development.

[2]  M. Yacoub,et al.  Anatomy of the muscular subpulmonary infundibulum with regard to the Ross procedure. , 2000, Annals of Thoracic Surgery.

[3]  A. Moorman,et al.  Myocardialization of the cardiac outflow tract. , 1999, Developmental biology.

[4]  M. Morishima,et al.  Developmental spectrum of cardiac outflow tract anomalies encompassing transposition of the great arteries and dextroposition of the aorta: Pathogenic effect of extrinsic retinoic acid in the mouse embryo , 1999, The Anatomical record.

[5]  T. Mikawa,et al.  Neural crest cells in outflow tract septation of the embryonic chicken heart: Differentiation and apoptosis , 1998, Developmental dynamics : an official publication of the American Association of Anatomists.

[6]  M. Kirby,et al.  Cardiac neural crest cells provide new insight into septation of the cardiac outflow tract: aortic sac to ventricular septal closure. , 1998, Developmental biology.

[7]  A. Moorman,et al.  Normal development of the outflow tract in the rat. , 1998, Circulation research.

[8]  M. Morishima,et al.  Hypoplasia of cushion ridges in the proximal outflow tract elicits formation of a right ventricle‐to‐aortic route in retinoic acid‐induced complete transposition of the great arteries in the mouse: Scanning electron microscopic observations of corrosion cast models , 1996, The Anatomical record.

[9]  F J Verbeek,et al.  Design and implementation of a database and program for 3D reconstruction from serial sections: A data‐driven approach , 1995, Microscopy research and technique.

[10]  Viktor Hamburger,et al.  A series of normal stages in the development of the chick embryo , 1992, Journal of morphology.

[11]  Robert H. Anderson,et al.  The Heart: Structure in Health and Disease , 1992 .

[12]  J. Icardo.  Development of the Outflow Tract , 1990, Annals of the New York Academy of Sciences.

[13]  Robert P. Thompson,et al.  A computer graphic study of cardiac truncal septation , 1983 .

[14]  T. P. Fitzharris,et al.  Morphogenesis of the truncus arteriosus of the chick embryo heart: tissue reorganization during septation. , 1979, The American journal of anatomy.

[15]  J. Drukker,et al.  Development of peripheral nerve and its reaction to axotomy. , 1978, Acta morphologica Neerlando-Scandinavica.

[16]  M. de la Cruz,et al.  Experimental study of the development of the truncus and the conus in the chick embryo. , 1977, Journal of anatomy.

[17]  R. Anderson,et al.  Morphogenesis of bulboventricular malformations. I. Consideration of embryogenesis in the normal heart. , 1974, British heart journal.

[18]  C. Lillehei,et al.  The Conotruncus: I. Its Normal Inversion and Conus Absorption , 1972, Circulation.

[19]  R. D. Alley,et al.  Pathogenesis of transposition Complexes , 1963 .

[20]  R. F. Shaner.  Comparative development of the bulbus and ventricles of the vertebrate heart with special reference to Spitzer's theory of heart malformations , 1962, The Anatomical record.

[21]  B. M. Patten,et al.  Valvular action in the embryonic chick heart by localized apposition of endocardial masses , 1948, The Anatomical record.

[22]  T. Kramer.  The partitioning of the truncus and conus and the formation of the membranous portion of the interventricular septum in the human heart , 1942 .

[23]  Fons J. Verbeek,et al.  A Graphical Database for 3D Reconstruction Supporting (4) Different Geometrical Representations , 1998 .

[24]  Los Ja.  Cardiac septation and development of the aorta, pulmonary trunk, and pulmonary veins: previous work in the light of recent observations. , 1978 .

[25]  J. A. Los.  Cardiac septation and development of the aorta, pulmonary trunk, and pulmonary veins: previous work in the light of recent observations. , 1978, Birth defects original article series.

[26]  T. Pexieder.  Development of the outflow tract of the embryonic heart. , 1978, Birth defects original article series.

[27]  H. Laane.  The septation of the arterial pole of the heart in the chick embryo. II. Development of the truncus arteriosus of the heart of chick embryos from 4 to 5 days of incubation. , 1978, Acta morphologica Neerlando-Scandinavica.

[28]  R. D. Alley,et al.  PATHOGENESIS OF TRANSPOSITION COMPLEXES. I. EMBRYOLOGY OF THE VENTRICLES AND GREAT ARTERIES. , 1963, The American journal of cardiology.

[29]  O. Hertwig.  Handbuch der vergleichenden und experimentellen entwicklungslehre der wirbeltiere, bearb. von prof. dr. Barfurth [u.a.] hrsg. von Oskar Hertwig. , 1906 .

[30]  Morris Tonge.  Observations on the development of the semilunar valves of the aorta and pulmonary artery of the heart of the chick , 1868, Proceedings of the Royal Society of London.