day 8, the blastocyst arrives in the uterus and implants in the endometrium becoming an embryo. This ends the germinal period and begins the embryonic period of prenatal development.
pregnancy does not occur until the Conceptus undergoes rapid cell division and implants into the uterine lining
When sperm and egg unite, a Zygote is formed
the zygote divides into two cells, then four, then eight . . . and so forth.
By the third day, a small, hollow ball of 32+ cells has grown.
cluster of cells within the blastocyst will develop into the body and the outer layers will become supporting structures, such as the amniotic sac and placenta, during gestation .
same time that pregnancy can be detected.
key processes in prenatal development beyond cell division and replication: folding, instruction, death, and migration
When cells at specific locations cause tissue to bend, the folding results in complex shapes
Cell instruction refers to chemical signals that tell cells where they are and what they are to do relative to other cells
When certain cells are killed, body structures are refined (e.g., cells between fingers and toes;
Cells also reorganize by migrating or traveling to different areas (e.g., brain; Polleux & Anto
Highlights of prenatal development
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