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Survey of Pregnancy and embryonic development

Page 563. Survey of Pregnancy and embryonic development. Accomplishing Fertilization.

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Survey of Pregnancy and embryonic development

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  1. Page 563 Survey of Pregnancy and embryonic development

  2. Accomplishing Fertilization • For fertilization to occur, sexual intercourse must occur no more than 2 days before ovulation and no later than 24 hours after, at which point the oocyte is approximately one-third of the way down the length of the uterine tube. • Sperm are attracted to the oocyte by chemicals that act as “homing devices” • It takes 1-2 hours for sperm to complete the journey up the female duct system into the uterine tubes • Only a few hundred to a few thousand sperm make it to the egg’s vicinity; the rest are destroyed by the acidic environment

  3. What is a zygote? • Fertilized egg that forms the moment the genetic material of a sperm combines with the ovum • First cell • Zygote undergoes rapid mitotic divisions; this is known as cleavage. • Daughter cells become smaller and smaller, providing a large number of cells for constructing the embryo.

  4. Embryo (developing stage until the 9th week) • By the time the developing embryo reaches the uterus is has formed into a morula • Morula- 3 days after ovulation; tiny ball of 16 cells • Free floating in uterine cavity.

  5. Embryo continues to develop until it has about 100 cells and then hollows out into a blastocyst • attaches to the endometrium by day 7 • The blastocyst secretes human chorionic gonadotropin (hCG) hormone • Maintains hormone production of the corpus luteum and prevents menses • Confirms pregnancy in urine for home pregnancy kits

  6. Three primary germ layers: • Ectoderm- nervous system, skin • Endoderm- mucosae (organ linings), lungs, liver • Mesoderm- muscle, bone, blood, heart

  7. Placenta • Temporary organ formed from a fertilized egg and mother’s uterine tissues to provide nutrients and oxygen to a developing fetus • Carries away wastes • Produces hormones of pregnancy • Attached by umbilical cord • Fully functioning by end of second month

  8. Amnion • Fluid-filled sac that surrounds the embryo • Attached to the placenta by a blood vessel-containing stalk of tissue called the umbilical cord • Ruptured when “water-breaks” prior to delivery • By the 9th week of pregnancy the embryo is known as the fetus

  9. Pregnancy • By approximately 270 days after fertilization, the fetus is said to be “full-term” and is ready to be born • Pregnancy is the period from conception to the birth of her baby

  10. Anatomical changes • Uterus enlarges pushing organs against the diaphragm, widening the ribs • Uterus reaches the xiphoid process • Relaxin hormone causes pelvic ligaments and the pubic symphysis to relax, widen, and become more flexible

  11. Physiological Changes • Nausea or “morning sickness” • Heartburn due to stomach displacement • Constipation due to limited motility of the digestive tract • Kidneys produce more urine and uterus compresses bladder • Nasal stiffness and occasional nosebleeds • Additional blood volume, increased blood pressure and pulse

  12. Development • Embryo- 1st 8 weeks of pregnancy. Fetus- 9th week to birth. • Month 1: nervous system begins; limb buds. • Month 2: 1g; large head; heart beats; bone form; digits. • Month 3: 30g; facial features; blood; sex detected. • Month 4: 100g; body elongates; human face • Month 5: .5-1lb; fetal position; quickening (muscular activity); lanugo • Month 6: 1.5lb; substantial weight gain, wrinkled skin • Month 7: 3lb; testes descend; eyes open; viable • Month 8: 5lb; subcutaneous fat; skin less wrinkled • Month 9: 7.5 lb; lanugo shed; full nails

  13. Childbirth • Childbirth aka parturition • Usually occurs within 15 days of the calculated due date (280 from last menstrual period) • Laboris the series of events that expel the infant from the uterus

  14. http://www.ewtn.com/library/prolife/pregnancy.htm • http://www.baby2see.com/gender/external_genitals.html • http://www.babycenter.com/fetal-development-week-by-week • http://www.squidoo.com/eat-human-placenta

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