The relation of the sino-auricular node to the venous valves in the human heart.код для вставкиСкачать
THE RELATION OF THE SINO-AURICULAR NODE TO THE VENOUS VALVES I N THE HUMAN HEART ADELII: OPPENHEIMER AND B. S. OPPEXHEIMER From the Prcthological Laboratory of Columbia Universitg O N E FIGURE The reason for publishing this finding in the human heart is to present evidence that the sino-auricular node lies within the region which corresponds to the sinus venosus of the cold-blooded vertebrates. The sino-auricular node is now believed by many to be the site of origin of the heart beat in mammals,’ just as the sinus venoms is known to be the primum movens in the coldblooded vertebrates. I n the lower vertebrate heart, the sinus venosus is a distinct chamber separated from the auricular canal by the venous valves, so that the free margin of the valves forms the boundary line between the cavity of the sinus and that of the auricular canal. But as in the adult human heart the venous valves in this region have been greatly modified and shifted in position, it has not been definitely shown on which side of the valve the sino-auricular node is located. I n the hearts of the two foetuses and the one child’s heart about to be described we found the venous valve present and the sinoauricular node (that is the pacemaker of the heart) to the sinus side of the valve. The hearts, which were secured through the courtesy of Dr. E. A. Park and Dr. B. Rosenbluth, were from an infant three weeks old which had died of pneumonia and from two foetuses 16 em. and 21 cm. long, respectively. Upon gross examination the infant’s heart was found to be normal. The heart was fixed in allialinized formalin. For microscopic exami1 See the work of Wybauw, Lewis and Oppenheimer, Cohn and Kessel, Brandenburg and Hoffmann, Ganter and Znhn, and the opinions of W. Koch and of Hering. 487 488 ADELE O P P E N H E I M E R AND B. S . O P P E N H E I M E R nation the region of the sino-auricular node was excised. This block consisted of the wall of the right auricle on either side of the sulcus terminalis of His; extending dorsad as far as, and including a portion of the endocardium of the left auricle and a part of the superior and inferior venae cavae, extending ventrad beyond the crista terminalis of His so as to include a strip of pectinate muscles all along the length of the crista. Moreover this bIock extended along both sides of the crest of the right auricle, thus including not only the part already described on t h e lateral aspect of the auricle on either side of the sulcus, but also the auricular wall on the median aspect facing the aorta. On the lateral aspect the area reached almost to the auriculo-ventricular groove; on the median face it extended from the crest down t o the level of the origin of the aorta. This piece was embedded in celloidin-paraffin,cut into sections 15 micra thick, and stained with Weigert’s iron-haematoxylin and van Gieson’s picric-acid fuchsin solution. The sections were horizontal, that is perpendicular to the length of the crista terminalis of His and to the epi- and endocardium. On microscopic examination the typical nodal tissue was found in the usual position, namely, at the junction of the superior vena cava with the right auricle and along the crista terminalis under the sulcus of His. The node could be identified even under low magnification by its wealth of connective tissue, crowded nuclei, and the dense syncytial character of its musculature; moreover by its relationship to its nutrient artery. At the junction of the node and crista a valvular cusp was found, as well as its companion cusp on the opposite side of the endocardium. These cusps consist of a central core of connective tissue with a few muscular elements, covered with a single layer of flattened endocardia1 cells. The crista and the pectinate muscles were situated anterior to the valves; the musculature of the superior vena cava, atrium and sino-auricular node posterior to the valves; the endocardium covering the auricular wall in front of the valves is thinner than that covering the auricular wall posterior t o them. I n Keith and Flack’s classic papers,2the position of the venous valve in the human heart was suggested in the exact situation in which we have actually found it in the heart here described. Keith and Flack identified the remnant of the sino-auricular junction in the human heart by comparing it with the turtle’s 2 Keith znd Flack, Jour. of Anat. and Physiol., 1907, vol. 41, p. 172. NODE A N D VALVES I N T H E HUMAN H E B R T 489 Fig. 1 Showing horizontal section of the right auricle in the region of the sinoauricular node of an infant’s heart. Photomicrograph X 16. 1-1, venous valve; 2, ordinary cardiac musculature; 3, musculature of the sino-auricular node; 4, taenia or crista terminalis of His, which, lined with thin endocardium, lies on the auricular side of the valve. The elongated cavity, lined with thick endocardium, is situated on the sinus side of the valve. 490 A D E L E O P P E N H E I M E R A N D B. S. O P P E N H E I M E R heart in which there is a venous valve. They showed (fig. 6 of their paper) that in the turtle’s heart the endocardia1 covering of the auricular musculature is thinner than that of the sinus, arid that the venous valve is situated at the junction of the two varieties of endocardium. I n the human heart here described and in the heart of the two foetuses examined, the sino-auricular junction as such is almost as clearly shown as in the more primitive hearts, for the venous valve is actually present lying between the musculature (auricular) covered by a thin endocardium and that (sinus) lined with a thick endocardium. The nodal tissue was found a t the base of the venous valve in the region covered by thick endocardium. The relations in the foetuses’ hearts were found to be the same as those in the infant’s. I n brief, in the infant and foetus’ hearts here presented the sino-auricular node lay in close proximity to the base of the venous valve, in what! corresponds t o the sinus venosus of cold-blooded vertebrates.