The embryo is most sensitive to outside influences that can cause malformations during the
A)first two weeks after fertilization.
B)third to the ninth weeks of development.
C)ninth to the sixteenth weeks of development.
D)twelfth to the twentieth weeks of development.
E)twenty-first to twenty-sixth week of development.

Question

Quizplus · Accepted Answer

During the third to the ninth weeks of development, the major organs and structures are being formed, and any outside influences such as drugs, radiation, or infections can cause malformations or developmental abnormalities. This is known as the embryonic period of development. The first two weeks after fertilization are the period of cleavage and implantation, where the zygote divides and implants in the uterine wall, while the later stages of development (ninth to sixteenth week and beyond) are known as the fetal period of development, where the organs continue to grow and mature but are less susceptible to major malformations caused by environmental factors. The twelfth to twentieth weeks are when the fetus undergoes significant physical growth and development, but the major organs and structures have already formed by this point. The twenty-first to twenty-sixth weeks are considered the middle of the fetal period, where the fetus continues to develop and mature but is still not as vulnerable to outside influences as during the embryonic period.

The Embryo Is Most Sensitive to Outside Influences That Can