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Development

A. Development during pregnancy 1. Fertilization 2. Formation of the morula 3. Development of the blastocyst 4. Implantation B. Embryonic development 1. Beginnings of organ systems 2. Embryonic membranes

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Development

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  1. A. Development during pregnancy 1. Fertilization 2. Formation of the morula 3. Development of the blastocyst 4. Implantation B. Embryonic development 1. Beginnings of organ systems 2. Embryonic membranes 3. Placenta and umbilical cord C. Fetal growth D. Hormones of pregnancy E. Partuition and labor F. Adjustments of the infant at birth 1. Respiratory system 2. Cardiovascular system G. Physiology of lactation Development

  2. What is pregnancy (gestation)? • 266 days (lasts from conception to childbirth) • (gestation calendar 280 days (40 weeks) from 1st day of LMP) • What is fertilization? • Union of sperm and egg • How many sperm reach the ovum? • (2,000 – 3,000) out of 300 million in ejaculate reach the ovum vicinity • Where and when does fertilization occur? • Arrive within 5 – 10 minutes of ejaculation? • fertilization occurs in ampulla of oviduct

  3. Factors that affect sperm movement towards the ovum • 1. lashing of tails (flagellum) • 2. guided by strands of cervical mucus • 3. prostaglandins in semen • 4. uterine tenting and contractions • 5. chemical attractant from the ovum?

  4. What is capacitation? • requires ~10 hours • female fluids remove cholesterol from sperm membranes • sperm membrane becomes more fragile • Viability of sperm -6 days in female reproductive tract “window of opportunity” = a few days before ovulation to 14 hr after (causes it takes another 10 hours for capacitation) (Margin of error does exist)

  5. Fertilization • 1. acrosome reaction hyaluronidase and acrosin • 2. barriers a. corona radiata b. zona pellucida c. egg cell membrane • 3. genetic events • 4. zygote • 5. blocks to polyspermy (fast vs. slow)

  6. Cleavage • 1. blastomeres - Zygote to 16 cells • 2. morula -free in uterus 4-5 days - 100 cells • 3. blastocyst a. trophoblast b. inner cell mass c. blastocoel Lots of mitosis

  7. Implantation • 1. occurs 6 days after ovulation in fundus of posterior wall of uterus • 2. trophoblast -invasion of stratum functionalis • 3. accomplishments - formation of the chorion (fetal placenta) - human chorionic gonadotropin (hCG) secretion

  8. Summary of Fertilization and Implantation

  9. Stages of Development • Prembryonic Stage (0- 16 days) • Embryonic Stage (16 days to 8 weeks) • Fetal Stage ( 8- 40 weeks)

  10. Embryonic Period • 1. weeks 3 – 8 ( 16 days to 8 weeks) • 2. gastrulation • 3. primary germ layers a. ectoderm b. endoderm c. mesoderm

  11. The Developing Human

  12. Extraembryonic membranes 4 weeks • 1. yolk sac • 2. amnion • 3. chorion • 4. allantois 12 weeks

  13. Extraembryonic Membranes

  14. Placenta and Umbilical Cord • Placenta 1. fetal vs maternal 2. functions • Umbilical cord 1. 2 umbilical arteries 2. 1 umbilical vein 3. Wharton's jelly 4. umbilicus

  15. Fetal period (weeks 9 - 38)

  16. Fetal Development and Risk

  17. Hormones of Pregnancy • 1. human chorionic gonadotropin • 2. estrogen • 3. progesterone • 4. human chorionic somatomammotropin • 5. relaxin

  18. Parturition and labor • Uterine Contractility false labor (Braxton Hicks contractions) true labor = parturition Positive Feedback of Labor begin ~30 minutes apart  progress to every 1 – 3 minutes cervical stretch  neuroendocrine reflex  oxytocin secretion uterine contraction  more stretch  repeat • 1. stage of dilation • 2. stage of expulsion • 3. placental stage

  19. Respiratory system adjustments at birth • CO2 accumulates in baby’s blood and strongly stimulates the respiratory chemoreceptors • First two weeks 45 bpm, then 12 bpm

  20. Cardiovascular System Changes at Birth • 1. foramen ovale -->fossa ovalis • 2. ductus arteriosus -->ligamentum arteriosum • 3. ductus venosum -->ligamentum venosum • 4. umbilical vein -->ligamentum teres • 5. umbilical arteries -->median umbilical ligaments

  21. Physiology of Lactation • 1. What is lactation? • 2. How are the breasts prepared? estrogens and other hormones causes duct growth and branching progesterone causes development of secretory acini steroids prevent milk synthesis • 3. Why do the breasts NOT need to produce milk until a couple of days after birth? Infants are born with excess body water and fat Colostrum(1/3 less fat, and lots of immunoglobulins) secreted for the first 3 days placental delivery = no estrogens and progesterone secretion milk synthesis now begins

  22. Physiology of Lactation • 4. What is the neuroendocrine reflex that lactation? a. Tactile stimulation of areola and nipple causes b. Sensory input to hypothalamus, leading to c. Secretion of oxytocin and prolactin from pituitary gland (1) Oxytocin stimulates contraction of myoepithelial cells of mammary glands, leading to milk letdown (2) Prolactin stimulates renewed milk synthesis by mammary gland cells

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