Book Notes 2

Book Notes 2 - Book Notes-Exam 2 Prenatal Development and...

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Unformatted text preview: Book Notes-Exam 2 Prenatal Development and the Newborn Period: Chapter 2 Prenatal Development o Aristotle- does prenatal life start with the new individual already preformed with a full set of tiny parts, or do the parts develop in succession? Preformationism-rejected by him Epigenesis- the emergence of new structures and function in the course of development o Conception Gametes (germ cells)- reproductive cells (egg and sperm) that only contain half the genetic material of all the other cells in the body Process starts with the launching of an egg from one of the womans ovaries into the fallopian tube It emits a chemical come hither signal to attract sperm If sexual intercourse takes place near the time the egg is released conception-the union of an egg from the mother and sperm from the father becomes possible As soon as the sperms head penetrates the outer membrane of the egg, the membrane is sealed, the sperms tail falls off, and the contents spill into the head Zygote- a fertilized egg Half genetic material from father and half from mother o Developmental Processes Embryo- the name given to the developing organism from the 3 rd- 8 th week of prenatal development Fetus- the name given to the developing organism from the 9 th week-birth Cell Division Within 12 hours, the zygote divides into 2 parts 2 parts 4 parts 8 16etc Cell Migration Movement of newly formed cells to somewhere else Cell Differentiation Stem cells- embryonic cells, which can develop into any type of body cell After several cell divisions, cells start to specialize in terms of structure and function Death Apoptosis- genetically programmed cell death o Ex: the death of cells between ridges in the hands so that fingers can grow Hormones play a crucial role in sexual differentiation What causes development to proceed one way or the other is the presence or absence of testosterone o Present- male o Absent- female o Early Development The 4 th day after conception: cells arrange themselves into a hollow sphere with a bulge of cells inner cell mass Identical twins- twins that result from the splitting in half of the zygote, resulting in each of the 2 resulting zygotes having exactly the same set of genes Fraternal twins- twins that result when 2 eggs happen to be released into the fallopian tube at the same time and are fertilized by 2 different sperm; they only have half their genes in common No more alike genetically than pairs of non-twin siblings By the end of the 1 st week: implantation- the zygote implants itself in the uterine lining and becomes dependent on the mother for sustenance Becomes completely embedded by 2 nd week Cells start to differentiate Inner mass- embryo o 3 parts Top- nervous system, nails, teeth, inner ear, lens of the eyes, outer surface of the skin Middle- muscles, bones, circulatory system,...
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Book Notes 2 - Book Notes-Exam 2 Prenatal Development and...

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