Section V. INTRAUTERINE DEVELOPMENT
The site of fertilization (when it occurs) is usually in the uterine tube. Initial
development of the embryo also takes place in the uterine tube. However, most
development is intrauterine (within the uterus).
a. Embryo. During the first 8 weeks of development, the developing individual
is called an embryo. The processes by which the embryo develops are studied in
b. Fetus. During the remainder of the intrauterine period, the developing
individual is known as the fetus. During this latter period, the details of structure and
9-20. SUPPORT OF THE EMBRYO AND FETUS
In paragraph 9-15b(2), we discussed the amniotic sac, umbilical cord, and
placenta. During intrauterine development, the embryo/ fetus is within the amniotic sac.
Floating free in the amniotic fluid, it is connected to the placenta by the umbilical cord.
The placenta is the specific area of exchange between the maternal blood and the fetal
blood. By this exchange, the fetus gets rid of waste materials and acquires food,
oxygen, and other needed substances from the mother.
Section VI. PARTURITION
Parturition is the process of childbirth.
9-22. INITIAL PHASE
The initial phase includes dilation (stretching) of the uterine cervix. At the
appropriate moment, the amniotic membranes rupture and release the amniotic fluid.
9-23. PASSAGE OF THE FETUS
The release of amniotic fluid is followed by the passage of the fetus through the
a. During this passage, the newborn makes two partial rotations to
accommodate the diameters of the relaxed bony pelvis.