Maternity and child care . and formswhat is known as the bag of waters at thetime of birth. This fluid serves four purposes: it forms acushion of water around the fetus which pro-tects it from injury through any jar or blow tothe abdomen; through pressure from tight cor-sets or clothing; or through sudden changes oftemperature, and it forms the bag of waterswhich is so important in dilating the mouth ofthe womb at the time of labor. Now let us again turn attention to the outerenvelope or the chorion. The cells which make upthis layer begin to grow outward, projectinglike fingers or the branche
Maternity and child care . and formswhat is known as the bag of waters at thetime of birth. This fluid serves four purposes: it forms acushion of water around the fetus which pro-tects it from injury through any jar or blow tothe abdomen; through pressure from tight cor-sets or clothing; or through sudden changes oftemperature, and it forms the bag of waterswhich is so important in dilating the mouth ofthe womb at the time of labor. Now let us again turn attention to the outerenvelope or the chorion. The cells which make upthis layer begin to grow outward, projectinglike fingers or the branches of a tree. There arethousands of these processes, called villi, andjust where the little embryo has sunk into thelining of the uterus, they develop in great num-bers and grow to greater length and size thanthe villi covering the rest of the sac. Theyextend right through the blood vessel walls of themembrane lining the uterus and are thus bathedin the mothers blood. This is the way in which THE EMBRYOS GROWTH AND FOOD 23. Cross Section of Pregnant Uterus{After Allen Thompson)This Diagram Shows the Relations of the Uterus, the Embryo,and the Embryonic Structures at the Second Month ofGestation. 1—Wall of uterus. 2—Beginning of fal-lopian tube. 3—Placenta showing branches of —Umbilical cord. 5—Fetus. 6—Amnionicfluid or bag of waters. 7—Amnionicmembrane. 8—Chorionic —Cervix or mouth of uterus. 24 MATERNITY AND CHILD CARE the mother cake, the placenta or after-birthas it is also called, is formed. At this point within the sac the embryo isgrowing and becomes attached to the placentaby a tiny tubular membrane which becomes thenavel cord. This navel or umbilical cord entersthe body of the fetus at the center of the abdo-men. Blood vessels are later formed within thiscord, one of which carries the blood from theplacenta to the fetus and two of which carrythe blood from the fetus to the placenta. Beforethe blood vessels form, the embryo absorbs nour
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