The development of the sino-atrial region of the chick heart


  • D. P. Quiring

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    • It is a pleasure to acknowledge my indebtedness to Dr. Bradley M. Patten, of the Department of Histology and Embryology of the Medical School of Western Reserve University, for suggesting this problem and for help in interpreting various findings, as well as for the use of series and dissections from his collection of chick embryos; to Dr. Frederick C. Waite, of the same department, for the loan of material from the teaching collection; to Dr. J. Paul Visscher, of the Biological Laboratory of Western Reserve University, for the use of laboratory materials and facilities; and to Dr. John L. Bremer, of Harvard Medical School, for the use of series from the Harvard Embryological collection.


The development of the interatrial septum and the relation of the sinus venosus and sino-atrial valves to the interatrial septum was followed in chick hearts ranging from 50 hours of incubation to the adult. The following singificant facts were established. The interatrial septum first appears at about 50 to 55 hours of incubation. It fuses with the endocardial cushions of the atrio-ventricular canal, typically in the last quarter of the fifth day. Secondary perforations appear in the septum at the time of closure of the interatrial foramen primum. These are retained until hatching, although they may persist in the adult heart. The sinus venosus, a sinus septum, and the sino-atrial valves are retained as definite structures in the adult fowl heart. The pulmonary vein and the left precava as they enter the heart form a prominent addition to the inter-atrial septum proper which I have designated as the pars cavo-pulmonalis. The pulmonary orifice in the left atrium is provided with an extensive flap-like valve. A prominent limbus of Vieussens is present in the right atrium. A well-developed median muscular arch overlies the interatrial septum and a pair of lateral muoscular arches extend over the atria. Their position would seem to be significant in the closing septal perforations during atrial systole.