. Anatomy, descriptive and applied. Anatomy. Fig. 536.—Heart showing expansion of auricles. (Drawn from Edier-Ziegler model.) coronary sinus (Fig. 494). The vitelline and umbilical veins are soon replaced by a single vessel, the inferior vena cava, and the three veins (inferior vena cava and right and left Cuvierian ducts) open into the dorsal aspect of the auricle by a common slit-like aperture (Fig. 542). The upper part of this aperture represents the opening of the adult superior vena cava, the lower that of the inferior vena cava, and the intermediate part the orifice of the coronary sinus
. Anatomy, descriptive and applied. Anatomy. Fig. 536.—Heart showing expansion of auricles. (Drawn from Edier-Ziegler model.) coronary sinus (Fig. 494). The vitelline and umbilical veins are soon replaced by a single vessel, the inferior vena cava, and the three veins (inferior vena cava and right and left Cuvierian ducts) open into the dorsal aspect of the auricle by a common slit-like aperture (Fig. 542). The upper part of this aperture represents the opening of the adult superior vena cava, the lower that of the inferior vena cava, and the intermediate part the orifice of the coronary sinus. The slit-like aperture lies obliquely, and is guarded by two valves, the right and left venous valves, which unite with each other above the opening and are continuous with a fold named the septum spurium. The left venous valve practically disappears, while the right is subsequently divided to form the Eustachian and Thebesian valves. At the lower extremity Aortic bitlb Left auricle Left rentricle.^ Might .Superior vena cava. •Septum transversitm. ?Umbilical vein. Vitelline or Omphalomesenteric vein. Fig. 537.—Heart of human embryo, mm. long, seen from behind. fHis.) of the slit is a triangular thickening, the spina vestibuli of His, which partly closes the aperture between the two auricles, and, according to His, takes a part in the formation of both the inter- auricular and interventricular septa. The auricular canal is at first a short straight tube connecting the auricular with the ven- tricular portion of the heart, but its growth is relatively slow, and it becomes overlapped by the auricles and ventricles so that its position on the surface of the heart is indicated only by an annular constriction. (Fig. 536). Its lumen is reduced to a transverse slit, and two thickenings appear, one on its dorsal and another on its ventral wall. These thickenings, or evdocardial cushions (Fig. 542), as they are termed, project into the canal, and, meeting in the mid
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
