. A laboratory manual and text-book of embryology. Embryology. 282 THE DEVELOPMENT OF THE VASCULAR SYSTEM mesonephroi, posterior extremities and dorsal body wall is in early stages drained by the posterior cardinal veins alone. The development of the unpaired vena cava inferior begins when communica- tion is established between the right hepatic vein of the liver and the right sub- cardinal vein of the mesonephros, primarily a tributary of the posterior cardinal vein (Lewis, 1902). The liver on the right side becomes attached to the dorsal body wall and from its point of union a ridge, the pli
. A laboratory manual and text-book of embryology. Embryology. 282 THE DEVELOPMENT OF THE VASCULAR SYSTEM mesonephroi, posterior extremities and dorsal body wall is in early stages drained by the posterior cardinal veins alone. The development of the unpaired vena cava inferior begins when communica- tion is established between the right hepatic vein of the liver and the right sub- cardinal vein of the mesonephros, primarily a tributary of the posterior cardinal vein (Lewis, 1902). The liver on the right side becomes attached to the dorsal body wall and from its point of union a ridge, the plica vena? cavae (Fig. 192), extends caudalward. According to Davis (1910), capillaries from the subcardinal vein invade the plica Confluence off he sinuses icJdle cerebral Tosterior cerebral i/etn. Superior petrosal sinus Transverse, Sinus Ophthalmic vem Ophthalmic vein jolirory vesicle Inf. petrosal sinus Trigeminal nerve Fig. 276.—Four diagrams showing the development of the veins of the head (after Mall). A, at four weeks; B, at five weeks; C, at the beginning of the third month; D, from an older fetus. venae cavae and, growing cranially, meet and fuse with capillaries extending caudad from the liver sinusoids. Thus is formed the vein of the plica vence cavce, which is already present in human embryos of mm. (Kollmann). This vein rapidly enlarges as also do the sinusoidal connections between the subcardinals and posterior cardinals at one point. Thus the blood from the lower posterior cardinals is soon carried to the heart, chiefly by way of the right subcardinal and right hepatic veins (Fig. B, 274 ). Soon the posterior cardinals just cranial to their enlarged anastomoses with the subcardinals become small and are interrupted. Cranial to their inter-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original wo
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