12 8 Conception and Prenatal Development MATCHING KEY TERMS Match the term with the correct definition. 1. autosome 2. conceptus 3. corpus luteum 4. embryo 5. gamete 6. mitosis 7. oogenesis 8. ovulation 9. placenta 10. somatic cell Results of a fertilized ovum Developing baby from weeks 3 through 8 c. Non sex chromosome d. Reproductive cell e. Ordinary body cell f. Structure that provides nourishment for developing baby g. Cells that remain after ovum formation and secrete estrogen and progesterone h. Formation of female gametes i. Cell division in body cells j. Release of the mature ovum from the ovary KEY CONCEPTS 1. Compare mitosis with meiosis in the following ways: Factor Mitosis Meiosis Type of cell involved Number and type of chromosomes in each resulting cell Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved. Chapter 12 Conception and Prenatal Development 59
2. Compare oogenesis with spermatogenesis in the following ways: Factor Oogenesis Spermatogenesis Number and type of chromosomes in each mature gamete Number of gametes resulting from each primary cell When gametogenesis begins and ends during life 3. What are the two major occurrences immediately after fertilization? 4. List three reasons why the fundus is the best area for implantation. c. 5. List the three germ layers and the structures that develop from each. c. 6. When during prenatal development does each event occur? Closure of the neural tube Heart contains four chambers c. All abdominal organs are within the abdominal cavity 60 Chapter 12 Conception and Prenatal Development Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
d. Eyes close e. Eyes reopen f. External ear development begins g. Fetal sex apparent by external genitalia h. Fetal movements felt by mother i. Surfactant production begins 7. Describe each of these fetal structures or substances and state their purpose. Vernix caseosa Lanugo c. Brown fat d. Surfactant 8. What is the difference between the fertilization age and the gestational age? 9. Explain how each of the following mechanisms allows the fetus to thrive in the relatively low-oxygen environment of the uterus. Fetal hemoglobin and hematocrit Relative fetal and maternal blood carbon dioxide levels Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved. Chapter 12 Conception and Prenatal Development 61
10. Describe how passage of maternal IgG antibodies can be either beneficial or harmful to the fetus. Beneficial Harmful 11. Explain the function of each placental hormone. Human chorionic gonadotropin (hcg) Human placental lactogen (hpl) c. Estrogen d. Progesterone 12. State the three functions of amniotic fluid. c. 13. Explain the umbilical cord structures and functions. Umbilical vein Umbilical arteries (two) c. Wharton s jelly 14. Explain factors that cause each of these fetal circulatory shunts to close after birth and the eventual outcome for each. Foramen ovale Ductus arteriosus 62 Chapter 12 Conception and Prenatal Development Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
c. Ductus venosus 15. Describe monozygotic and dizygotic twinning in the following terms. Factor Monozygotic Dizygotic Number of ova and sperm involved Genetic component Sex Hereditary tendency Number of amnions and chorions CRITICAL THINKING EXERCISES 1. A woman thinks she is pregnant but begins spotting (light vaginal bleeding). Her hcg levels are very low. What is the likely consequence of the low hcg level? Why? 2. What is a likely occurrence if a fetus is born with a lecithin-to-sphingomyelin (L/S) ratio of 1:1? Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved. Chapter 12 Conception and Prenatal Development 63
REVIEW QUESTIONS Choose the correct answer. 1. An important purpose of seminal fluid is to digest microorganisms in the female digestive tract. prevent premature movement of sperm tails. c. protect sperm from the acidic vaginal environment. d. transport the sperm into the uterine cavity. 2. Fertilization is complete when fusion of the sperm and ovum nuclei occurs. a sperm enters the ovum in the fallopian tube. c. the fertilized ovum has its first cell division. d. the morula fully implants into the uterine lining. 3. The embryo is fully implanted in the uterus on which day after conception? 3 6 c. 10 d. 15 4. Which fetal circulatory structure carries blood with the highest oxygen concentration? Umbilical artery Umbilical vein c. Ductus arteriosus d. Pulmonary vein 5. What is the significance of a fetal hemoglobin of 13 g/dl and a hematocrit of 39%? Fetal blood is more likely to clot as it circulates through the placent Greater transfer of carbohydrates will result in rapid fetal growth. c. Transfer of harmful substances from the mother to the fetus is lessened. d. Anemia reduces the oxygen-carrying capacity of the fetal blood. 64 Chapter 12 Conception and Prenatal Development Copyright 2009, 2005, 2000 by Saunders, an imprint of Elsevier, Inc. All rights reserved.