A manual of obstetrics . ng the latter months of preg-nancy the decidua undergoes a fatty degeneration that tendsto loosen its attachment to the uterus. The bulk of thisdegenerated membrane is thrown off at parturition; the bal-ance is discharged in the lochia, with the exception of asmall portion that assists in the formation of a new uterinemucosa. The Amiuon.—The amnion (Fig. 27) is a smooth, verytough, fibrous structure, the innermost of the fetal mem- 4 5 Fig. 26.—Diagrams representing the rela-tionship of the decidua to the ovum at dif-ferent periods. The deciduae are colored black,and t
A manual of obstetrics . ng the latter months of preg-nancy the decidua undergoes a fatty degeneration that tendsto loosen its attachment to the uterus. The bulk of thisdegenerated membrane is thrown off at parturition; the bal-ance is discharged in the lochia, with the exception of asmall portion that assists in the formation of a new uterinemucosa. The Amiuon.—The amnion (Fig. 27) is a smooth, verytough, fibrous structure, the innermost of the fetal mem- 4 5 Fig. 26.—Diagrams representing the rela-tionship of the decidua to the ovum at dif-ferent periods. The deciduae are colored black,and the ovum is shaded transversely. In4 and 5 the vascular processes of the chorionare figured, i, ovum entering the congestedmucous membrane of the fundus—decidua sero-tina ; 2, decidua reflexa growing around theovum ; 3, completion of the decidua around theovum ; 4, general growth of villi of the chorion ;5, special growth of villi at placental attach-ment, and atrophy of the rest (Dalton). 52 A MANUAL OF Fig. 27.—Diagram showing completion of theamnion and formation of the chorion : A, am-nion ; I, zona pellucida; 2, outer lamina of theepiblast after closure of the amniotic folds; P,allantois ; U, umbilical vesicle. branes, surrounding the fetus and continuous with it at theumbihcus; it secretes and encloses the Hquor amnii. Italso contributes the sheath or outer covering of the umbil-ical cord. Origin.—Thisstructure is a double mem-brane derived from theepiblast and mesoblast atan early period in fetal de-velopment. The enclosedspace is the true anmioticsac or cavity, and in this iscontained the liquor space between thefolds of the outer layer ofthe amnion—which is me-soblastic in origin, theinner being epiblastic—and the chorion is termedthe false amniotic contains the allantois,the umbilical vesicle, and, at times, a mucous fluid closelyresembling the liquor amnii, the hydroperione, previouslymentioned. At birth the amnion in con
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectobstetrics, bookyear1
