AntepartumNotes - Antepartum Chapter 6 Conception and...

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Antepartum Chapter 6: Conception and Prenatal Development I. Gametogenesis: development of ova/sperm (Table 6-1, p. 88) A. Oogenesis: formation of ova within ovary (Figure 6-1, A, p. 89) 1. Begins in prenatal life 2. Primitive ova (oogonia) multiply by mitosis (46 chromosomes) 3. Oogonia enlarge, forming primary oocytes surrounded by follicular cells (called primary follicle) 4. 1 st meiotic division begins in fetal life, but is incomplete until puberty 5. All ova the female will ever have are present by 30 th week of gestation 6. 1 st meiotic division is completed just before ovulation (now 23 chromosomes) 7. Begins to form mature ovum (2 nd meiotic division) a. 2 nd meiotic division does not complete unless the fertilization occurs 8. Hormones involved in oogenesis a. Gonadotropin releasing hormone (GnRH) b. Follicle stimulating hormone (FSH) c. Lutenizing hormone (LH) d. Estrogen 9. Each primary cell produces one ovum 10. Ova are large – visible to the naked eye 11. Non-motile B. Spermatogenesis: development of sperm cells (Figures 6-1, B, p. 89 and 6-2, p. 90) 1. Begins in puberty 2. Completes in 70 days 3. Primitive cells (spermatogonia) develop in prenatal period, and begin to divide my mitosis at puberty 4. 2 meiotic divisions: Primary spermatocyte meiotic division Secondary spermatocyte meiotic division spermatid maturation mature sperm C. Meiosis II. Conception A. Preparation for conception in the female 1. Release of the ovum (ovulation) a. Ova released about 14 days before the next menstrual period would begin b. Collapsed follicle forms the corpus luteum, which maintains secretion of estrogen and progesterone 2. Ovum transportation a. Mature ova are released from the surface of the ovary into the fimbrigated (fringed) end of the fallopian tube b. Transported by muscular action of the fallopian tube and cilliary action c. Fertilization occurs in the distal 1/3 of the fallopian tube d. Travel time of the ova from the ovary to the uterus is about 3 days B. Preparation for conception in the male 1. Ejaculation a. 40-250 million sperm (50-90% are morphologically normal) b. Seminal fluid nourishes and protects sperm 2. Transport of sperm in the female reproductive tract a. Propelled by tails from cervix uterus fallopian tubes b. <200 reach the correct fallopian tube 3. Preparation of sperm for fertilization a. Capacitation – glycoprotein coat and seminal protein are removed from the acrosome b. Sperm release hyaluronidase and acrosin to digest a pathway into the carona radiata and zona pellucida c. Tails beat harder C. Fertilization (Figure 6-3, p. 91) 1. Sperm entrance into ovum a. Changes of the zona pellucida prevent entry of other sperm b. Cell membranes of sperm and ovum break down c. Ovum completes 2 nd meiotic division 2. Fusion of the nuclei of sperm and ovum a. Nuclei move to the center of the ovum (now 46 total chromosomes) b. Cell division begins III. Pre-embryonic Period (Figure 6-4, p. 92) A. Initiation of cell division
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1. Solid ball of 12-16 cells called morula
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AntepartumNotes - Antepartum Chapter 6 Conception and...

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