890
UNIT SIX
FIGURE 23.15
The disc-shaped area where the chorion still contacts the uterine wall develops into the placenta.
FIGURE 23.16
The placental membrane consists of the
endothelium of an embryonic capillary and the epithelial wall of a
chorionic villus, as illustrated in the section of the villus (lower part
of the F
gure).
Chorion
Endometrium
Umbilical
cord
Amniotic cavity
Yolk
sac
Developing
placenta
Extraembryonic
cavity
Amnion
Allantois
Maternal
blood
vessels
Lacuna
filled with
maternal
blood
Artery
Vein
Chorion
Embryonic
capillaries
Chorionic villi
Maternal
blood
Wall of villus
Connective tissue
Placental
membrane
Section of villus
Umbilical cord
Umbilical arteries
Umbilical vein
Placenta
Endometrium
Lacuna
Villi
(embryonic portion
of placenta)
Decidua basalis
(maternal portion
of placenta)
Embryonic
blood vessels
Maternal
blood vessels
Chorion
Myometrium
FIGURE 23.17
The placenta consists of an embryonic portion and a
maternal portion.
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