. Cunningham's Text-book of anatomy. Anatomy. THE MEMBKANES AND APPENDAGES. oo Afferent vessel of villus. lasmodial trophoblast Cellular trophoblast Afferent vessel villus Mesoderm of villus f Efferent vessel >f villus embryo, arid as it contains the rudimentary allantoic diverticulum and represents the much more highly developed allantois of other forms, it might, with advantage, be named the allantoic stalk. For the present purpose it is important to note that the blood-vessels which pass through the body-stalk enter or leave the body through the umbilical orifice, which is, at first, a r
. Cunningham's Text-book of anatomy. Anatomy. THE MEMBKANES AND APPENDAGES. oo Afferent vessel of villus. lasmodial trophoblast Cellular trophoblast Afferent vessel villus Mesoderm of villus f Efferent vessel >f villus embryo, arid as it contains the rudimentary allantoic diverticulum and represents the much more highly developed allantois of other forms, it might, with advantage, be named the allantoic stalk. For the present purpose it is important to note that the blood-vessels which pass through the body-stalk enter or leave the body through the umbilical orifice, which is, at first, a relatively large aperture (Eig. 50). As the embryonic area is folded into the form of the embryo the amnion increases in extent, filling more and more of the extra-embryonic ccelom, and the embryo rises into the interior of its cavity. In other words, the walls of the amnion bulge ventrally round the cranial and caudal extremities and the lateral borders of the embryo (Figs. 75, 76, 77). As the distension of the amnion still continues, the ventral bulging round the margin of the umbilical orifice becomes more pro- nounced, the yolk-sac is forced farther and farther away from the embryo, the vitello-intestinal duct is elongated, and it is surrounded by a hollow tube. The cavity of the tube is an elongated part of the extra-embryonic ccelom, and its walls are formed by the amnion (Figs. 57,62,63). The caudal wall of the tube neces- sarily consists of the elongated body-stalk (allantoic stalk). As the distension of the amnion still continues, the walls of the tube are forced against the vitello -intestinal duct, and Fig of a Ti^ s^x of a p . , „ •. Secondary Chorionic villus. A loop ot tne the amniotic mesoderm tuses With the afferent vessel has been cut at two points. mesoderm of the vitello-intestinal duct. When the fusion is completed, a solid cord, the umbilical cord, is formed (Figs. 77, 78, 80). It consists of an external covering of amniotic ectoderm,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
