Chapter_3_Embryology - Chapter 3 Embryology I. Development...

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Chapter 3 Embryology I. Development a. Differentiation – formation and organization of all diverse cell types in body b. Reproduction – new individuals of the species are produced from generation to generation c. Prenatal period – first 38 weeks of human development, which occurs b/t fertilization of secondary oocyte and birth i. Pre-embryonic period – first 2 weeks (after fertilization) when zygote becomes spherical, blastocyst; period ends when blastocyst implants in the lining of uterus ii. Embryonic period – weeks 3 to 8; remarkably active time during which all major organ system appear in early form of an embryo iii. Fetal period – remaining 30 weeks of development prior to birth; fetus continues to grow and its organs increase in complexity d. Embryology – study of developmental events that occur during the prenatal period II. Figure 3.1 Developmental History of a Human a. Fertilization: Time zero b. Cleavage: Zygote 2-cell stage 4-cell stage Morula Blastocyst c. Gastrulation: Early 3 week Late 3 week Week 4 d. Organogenesis: Week 5 – 8 Birth e. Maturation continues after birth f. Gametogenesis occurs in adult III. Embryogenesis a. Embryogenesis – first development stage i. Cleavage – zygote divides by mitosis to form a blastocyst ii. Gastrulation – blastocyst cells form 3 primary germ layers, which are the basic cellular structures from which all body tissues develop iii. Organgenesis – 3 primary germ layers arrange themselves in ways that give rise to all organs w/in body b. Gametogenesis – second development stage i. Gametes – sex cells ii. meiosis and cytokinesis iii. Oogenesis – process of oocyte development REFER TO CH 28 NOTES iv. Spermagenesis – process of sperm development
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Chapter_3_Embryology - Chapter 3 Embryology I. Development...

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