The placenta is a fleshy disk like organ. The fully developed placenta (afterbirth)
is reddish in color. It is formed from the outer layers of the blastocyst. It is completely
formed by the third month of pregnancy. The umbilical cord (lifeline) connects the fetus
to the placenta and is normally 20 inches in length and 3/4 inch in diameter. It contains
one umbilical vein and two umbilical arteries.
FUNCTIONS OF THE PLACENTA
Being knowledgeable of the placenta functions gives insight into prenatal life and
is helpful in providing nursing care to the unborn and the newborn. The placenta
functions as a transport mechanism between the embryo and the mother (see
figure 2-6). The placenta has many tasks: it transports oxygen, nutrients, and
antibodies to the fetus by means of the umbilical vein; removes carbon dioxide and
metabolic wastes from the fetus by the two umbilical arteries; serves as a protective
barrier against harmful effects of certain drugs and microorganisms; acts as a partial
barrier between the mother and fetus to prevent fetal and maternal blood from mixing;
and produces hormones essential for maintaining the pregnancy. (The hormones are
estrogen, progesterone, and human chorionic gonadotropin (HCG)).
Figure 2-6. The placental circulation.