. The science and art of midwifery. , p. 141. 60 PHYSIOLOGY OF THE OVUM. vesicle. The larger size of the latter directs the allantois over theposterior extremity of the foetus. By its growth and extension, theallantois reaches the chorion, and forms a sort of pedicle, by means ofwhich a vascular communication is established between the embryoand the periphery of the ovum. This pedicle is the first indication ofthe umbilical cord. Its vessels become reduced to two arteries, theumbilical arteries, and a single vein, the umbilical vein. Meantime,the umbilical vesicle diminishes in size, and final
. The science and art of midwifery. , p. 141. 60 PHYSIOLOGY OF THE OVUM. vesicle. The larger size of the latter directs the allantois over theposterior extremity of the foetus. By its growth and extension, theallantois reaches the chorion, and forms a sort of pedicle, by means ofwhich a vascular communication is established between the embryoand the periphery of the ovum. This pedicle is the first indication ofthe umbilical cord. Its vessels become reduced to two arteries, theumbilical arteries, and a single vein, the umbilical vein. Meantime,the umbilical vesicle diminishes in size, and finally shrinks to a merethread. The amnion fills with fluid, exuded probably from the bodyof the foetus, and continues to expand, so that often by the end of thesecond month it comes in contact with the chorion.* In this way, itforms a reflection over the pedicle of the allantois, which it investslike the finger of a glove. Finally, the structure of the cord is com-pleted by the formation of an elastic substance, termed the gelatine of. Fig. 53.—A, umbilical arteries forming spirals CI, V) around the vein; constrictions indi-cating the presence of folds (3, 3) ; circular folds (5, 5) ; lateral openings showing thearterial walls. B, vein opened upon the side, showing a constriction (2) correspondingto an interior valve (3); semi-lunar valves (3, 3, 3 ). C, section of vein and arteriesshowing valve of vein (1), a semi-lunar arterial valve (2), and a circular arterial valve (3).(Tarnier et Chantreuil.) Wharton, which consists of connective-tissue elements inclosing largespaces containing amorphous matter. The gelatine of Wharton func-tionally serves to protect the vessels of the cord from compression. * Vide Huntersplate xxxiii, Fig. 7. Gravid Uterus, plate xxxiii, Fig. 2 ; Ecker, Icon. Physiolog, DEVELOPMENT OF THE OVUM. (ft It is formed by hypergenesis from the outer layers of the amnionand the allantois, both of which are derived from the intermediatelayer, described in the devel
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
