. Anatomy, descriptive and applied. Anatomy. 764 THE VASCULAR SYSTEMS portal vein; while the vessels draining the plexus into the sinus venosus are termed the venae, revehentes, and form the future hepatic veins (Figs. 545 and 546). Ultimately the left vena revehens no longer communicates directly with the sinus venosus, but opens into the right vena revehens. The lower part of the yortal vein is formed from the fused vitelline veins which receive the veins from the alimentary canal; its upper part is derived from the venous rings by the persistence of the left half of the lower and the right
. Anatomy, descriptive and applied. Anatomy. 764 THE VASCULAR SYSTEMS portal vein; while the vessels draining the plexus into the sinus venosus are termed the venae, revehentes, and form the future hepatic veins (Figs. 545 and 546). Ultimately the left vena revehens no longer communicates directly with the sinus venosus, but opens into the right vena revehens. The lower part of the yortal vein is formed from the fused vitelline veins which receive the veins from the alimentary canal; its upper part is derived from the venous rings by the persistence of the left half of the lower and the right half of the upper ring, so that the vessel forms a spiral turn round the duodenum (Fig. 546). The two umbilical veins fuse early to form a single trunk in the body stalk, but remain separate within the embryo and pass forward to the sinus venosus in the side walls of the body. Like the vitelline veins, their direct connection with the sinus venosus becomes interrupted by the inva- sion of the liver, and thus at this stage the whole of the blood from the yolk sac and placenta passes through the substance of the liver before it reaches the heart. The right umbilical vein becomes disconnected from the sinus venosus, shrivels, and forms a small vein of belly wall; the left, on the other hand, becomes enlarged and opens into the upper venous ring of the vitelline veins. Finally, a direct channel is established between this ring and the heart; this channel is called the ductus venosus, and, enlarging rapidly, forms a wide channel tlirough which most of the blood, returned from the placenta, is carried directly to the heart without being obliged to pass through the liver. The left umbilical vein and ductus venosus become impervious after birth, and form, respectively, the Ugamentum teres and Ugamentinn venosimi of the liver (Fig. 1071). Ventral detached portions of umbilical veins. y-, Stomach. Venae advehentes. - ~ Pancreas. -' Bile duct. -- Obliterated portions of venous rings. Righ
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
