Development Through the Lifespan, Berk Chapter 3

Conception - ANS Every 28 days an ovum is released from one of a woman's ovaries and remains viable for about 24 hours -Conception takes place in the Fallopian tube where sperm and ovum unite to form the zygote ovulation - ANS Most conceptions result from intercourse on the day of or in the two days preceding ovulation Once released in the vaginal canal, sperm remain viable for up to 6 days zygote - ANS The period of the zygote lasts about two weeks, from fertilization until the cell mass drifts out of the fallopian tubes and attaches itself to the uterine wall. By the 4th day Blastocyst blastocyst - ANS By the fourth day, 60 to 70 cells exist that form a hollow, fluid - filled ball embryonic disk - ANS The embryonic disk -cells inside the blastocyst) eventually develop into the embryo - The cells on the outside of the blastocyst protect the embryonic disk implantation - ANS the blastocyst burrows deep into the uterine lining occurs sometime between the seventh and ninth day when the blastocyst burrows deep into the lining of the uterus amnion - ANS encloses the developing organism in amniotic fluid, which helps keep the temperature of the prenatal world constant and provides a cushion against any jolts cause by the woman's movement amnion is a membrane that encloses the developing organism in amniotic fluid , which serves as a cushion and temperature regulator amniotic fluid - ANS The amnion is a membrane that encloses the developing organism in amniotic fluid, which serves as a cushion and temperature regulator The yolk sac - ANS produces blood cells until the liver, spleen, and bone marrow are mature enough to take over this function The yolk sac produces blood cells until the liver, spleen, and bone marrow are mature enough to take over this function • As many as 30% of zygotes do not make it through this phase As many as 30% - ANS of zygotes do not make it through this phase chorion - ANS a protective membrane, develops around the amnion by the end of the second week surrounds the aminion. from which villi or blood vessels emerge placenta - ANS is a special organ that permits food and oxygen to reach the zygote and waste products to be carried away umbilical cord - ANS connects the placenta to the developing organism which first appears as a tiny stalk and during the course of pregnancy grows to a length of 1 to 3 feet. contains one large vein that delivers blood loaded with nutrients and two arteries that remove waste products embryo - ANS lasts from implantation 2nd to the eighth week during this time the most rapid prenatal changes take place • The most rapid prenatal changes take place during these six weeks as the groundwork for all body structures and internal organs is begun • embryo can move and respond to touch Nervous system 1st During the third week, the embryonic disk folds over to form three cell layers: - ANS Ectoderm - - Mesoderm - - Endoderm - Neuromuscular system can be damaged - ANS Through most of the pregnancy Embryonic period - ANS Is most risky for teratogens is stress, smoking ect 2-8 weeks Ectoderm - ANS becomes the nervous system and skin Mesoderm - ANS develops into muscles, skeleton, circulatory system, and other internal organs Endoderm - ANS becomes the digestive system, lungs, urinary tract, and glands neural tube - ANS the ectoderm folds over to form this primitive spinal cord