Fertilization creates a zygote, which undergoes cell divisions and implants in the uterus. After implantation, it becomes an embryo and forms 3 cell layers, which differentiate and develop into different organs. At nine weeks, the embryo becomes a fetus, and the fetus continues to grow and takes nutrients from the placenta. During childbirth, uterus contractions push the baby out of the mother’s body. The baby grows rapidly throughout infancy and grows more slowly during childhood. During adolescence, children develop into adults. Starting in middle adulthood, health declines as cells lose their ability to divide.
Fertilization: Process in which two gamete cells unite.
Gamete: Reproductive cells.
Zygote: A fertilized cell (the result of fertilization).
Blastocyst: Ball of cells with a fluid-filled cavity inside.
Implantation: Process in which a blastocyst embeds in the endometrium lining the uterus.
Embryo: Stage of growth and development that occurs from implantation through the eighth week after fertilization in humans
Differentiation: Process where an unspecialized cell becomes specialized.
Fetus: The developing human organism between week eight and birth (typically 38 weeks).
Placenta: Temporary organ connecting mother to fetus that provides fetus with necessary nutrients.
Amniotic Sac: Membrane surrounding and protecting the fetus.
Pregnancy: Carrying offspring from fertilization until birth.
Infancy: First year of life after birth.
Adolescence: Period of life between puberty and adulthood
Fertilization takes place when the male gamete cell (sperm) and the female gamete cell (egg) unite
Pregnancy typically takes 38 weeks for humans.
Infancy is the fastest period of growth after birth
Adolescence is a period of significant changes
Adulthood does not have a definite starting point
Aging occurs as cells stop dividing and die. Two reasons that cells stop dividing are: