Prenatal Development Fertilization: Union of a sperm cell w/ an ovum. ~Fertilization takes place in the upper 1/3 of the fallopian tube. Zygote: Fertilized union, egg and sperm unite. ~Once zygote is formed, a protective membrane around it prevents more sperm from entering ovum. ~Zygote begins its journey to uterus and begins cell division. ~Once cell division has begun, zygote is now a blastocyst. DEVELOPMENT STAGES: Ova> Zygote> Blastocyst> Embryo> Fetus>Baby
Blastocyst: a cluster of cells that has a hollow space in the center. ~7-8 days later the blastocyst has traveled to the uterus and implanted into the wall of uterus. ~This is called implantation. ~ After implantation, the blastocyst becomes an embryo.
Embryonic Development Embryo: Cluster of developing cells following implantation. Amniotic Sac: Bag of water, fluid filled sac around the embryo. ~Function- Is a shock absorber that protects the embryo.
Placenta: Blood rich tissue developed from outer layer of cells from the embryo and tissue of mother. ~Function- Transfer oxygen and nutrients from mother’s blood to embryo also serves as lungs, liver, kidneys, and digestive system for fetus. Umbilical cord: A tube through which nutrients and oxygen pass from the mother’s blood to embryo’s blood. This tube connects the embryo to the placenta. Grows to 20 inches
After 56 days of development all major organs are formed and is now called a fetus.
Fetus is not called a baby until it is born and breathing on its own.
Blood of Mom & Fetus never mix All other nutrients and chemicals are shared! Miscarriage: Spontaneous abortion, in which a female expels the embryo or fetus. Stillbirth: The birth of a dead baby. ~Fetal Alcohol Syndrome(FAS): 3 main features- mental retardation, slow growth before and after birth, and a wide range of physical defects ranging from cleft palate to hip dislocation
Twins! Identical Twins – The zygote splits into 2 identical eggs These eggs now share a placenta Are always the same sex
Fraternal Twins These twins result from 2 separate eggs that fertilize at the same time, but with separate placentas. They can be same or different sex.