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Chapter 29: DevelopmentIntroductionFertilizationFirst Week of DevelopmentImplantationSecond Week of DevelopmentThird Week of DevelopmentFourth week of DevelopmentFifth Through Eight Weeks of DevelopmentFetal PeriodDuring the fetal period, tissue and organs that developed during the embryonic period grow and differentiate. The rate of body growth is remarkable.A summary of the major developmental events of the fetal period is presented in Table 29.2 and Figure 29.02.Hormones of PregnancyLabor and ParturitionAdjustments of the Infant at BirthChapter 29: Development Chapter Objectives INTRODUCTION 1. Differentiate between embryological development and fetal development. EMBRYONIC PERIOD First Week of Development 2. Describe the process of fertilization, including capacitation and how the sperm penetrates the three layers surrounding the secondary oocyte. 3. Describe the two processes that stop penetration of the egg by more than one sperm. 4. Explain the process of cleavage and state how this process leads to the formation of a morula. 5. Specify the features of the blastocyst that distinguish it from the morula and describe which parts of the blastocyst will develop into what structures. 6. Describe the process of implantation. 7. List the three regions of the decidua. Second Week of Development 8. Discuss the layers which develop from the trophoblast and state their function. 9. Discuss the formation and significance of the chorion. 10. Trace the development of the chorionic villi and placenta. 11. Explain the maternal and fetal parts of the placenta. 12. State the functions of the placenta. 13. Discuss the fate of the placenta after the birth of the baby. 14. Examine the development of the amnion and the formation of the amniotic fluid and state their function. 15. Discuss the formation and functions of the yolk sac. 16. Discuss the two layers that develop from the inner cell mass. Third Week of Development 17. Describe gastrulation and the growth of the three primary germ layers. 18. Establish which organs arise from the different germ layers by the end of the embryonic development. 19. Describe the process of neurulation and the formation of the neural tube. 20. Examine the formation of the mesoderm, the three regions of mesoderm and which structures are formed from each region. 21. Describe the formation of the cardiovascular system.Fourth Week of Development 22. Examine how embryonic folding converts the embryo to a three dimensional cylinder. 23. Trace the organ development that occurs during the fourth week of development. Fifth Through the Eighth Weeks of Development 24. Match the events in the rapid development of the embryo with the week it occurs during this period. FETAL PERIOD 25. Discuss the development of the fetus, which occurs during this period. Reference the pages indicated in the text that discuss the development of the various body systems. HORMONES OF PREGNANCY 26. Compare the sources and functions of the hormones secreted during pregnancy. LABOR 27. Outline the hormonal and neural regulation of the duration of pregnancy. 28. Describe the characteristics of the three stages of labor. ADJUSTMENTS OF THE INFANT AT BIRTH 29. Discuss the respiratory system adjustments of the infant at birth. 30. Discuss the cardiovascular system adjustments of the infant at birth. Chapter Lecture Notes Introduction Prenatal development - the time from fertilization until birth divided into three trimesters Embryonic period - the first two months (8 weeks) following fertilization the developing human is referred to as an embryo Fetal period - from week nine until birth the developing human is referred to as a fetus Fertilization Fertilization – the merger of oocyte and sperm (Fig 29.1) Oocyte - ovulated from ovary and then transported through the uterine tubeSperm - swim up the uterus and into the uterine tube by the whip like movements of their tails (flagella) and muscular contractions of the uterus Capacitation - final maturation of the sperm in preparation of fertilization acrosomal membrane becomes fragile allows sperm to fertilize a secondary oocyte occurs 6 to 8 hours after deposited in female Fertilization normally occurs in the uterine tube within 12 to 24 hours after ovulation A sperm must penetrate the corona radiata and zona pellucida around the oocyte A glycoprotein in the zona pellucida (ZP3) acts as a sperm receptor triggers the acrosomal reaction - release of the contents of the acrosome onto the zona pellucida Acrosomal enzymes digest a path through the zona pellucida allowing only one sperm to reach the oocyte’s plasma membrane Sperm enters a secondary oocyte The oocyte completes meiosis The male DNA and female DNA combine forming the fertilized ovum or zygote Syngamy - fusion of a sperm with a secondary oocyte First sperm to fuse with oocyte membrane triggers the slow & the fast block to polyspermy Fast block to polyspermy - 1-3 seconds after contact, oocyte membrane depolarizes & other cells can not fuse with it Slow block to polyspermy - depolarization triggers the intracellular release of Ca+2 causing the exocytosis of molecules hardening the entire zona pellucida First Week of Development Cleavage – early cell division of a zygote (Fig 29.2 & 29.5) cells become progressively smallerblastomeres - cells produced by cleavage 1st cleavage (30 hours) produces 2 blastomeres (2 cell embryo) 2nd cleavage (Day 2) produces 4 cell embryo 16 cell embryo (Day 3) morula (Day 4) - solid mass of more than 16 cells blastocyst (Day 5) – a hollow ball of cells developed from a morula that has the following structures trophoblast cells - will form the future embryonic membranes & fetal portion of placenta trophoblast secretes human chorionic gonadotropin (hCG) that helps the corpus luteum maintain the uterine lining inner cell mass or embryoblast cells - the future embryo blastocele - an internal fluid-filled cavity enters the uterine cavity by day 5 Implantation Implantation – attachment of a blastocyst to the endometrium (Fig 29.3, 29.5 & 29.6) the blastocyst remains free with the cavity of the uterus for two to four days hatching – breakdown and shedding of the zona pellucida by the blastocyst implantation occurs seven to eight days after fertilization Following implantation the endometrium is known as the decidua and consists of three regions: Decidua basalis - between the chorion and the stratum basalis of the uterus (Fig 29.4)


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MCC BIO 202 - Development

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