Lect 1 Student notes 09

Lect 1 Student notes 09 - BASIC EMBRYOLOGY Chapter 3 Dr...

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1 BASIC EMBRYOLOGY Dr. Phelps Chapter 3 Lecture 1 Most of this computer-based multimedia presentation is available on the Internet at: http://www.lsic.ucla.edu/classes/. Computers are available in the Boelter 2808 lab, the Science Learning Center (Young Hall South), and the Life Sciences Instructional Computing Laboratory. Key points that correlate with today's presentation are listed below and also on the web presentation. Human embryonic development takes an average of 38 weeks. First 8 weeks called Embryonic Period and remaining 30 weeks called Fetal Period. First week of development 1- Cross-section of female reproductive system Oocyte develops in ovary. After ovulation, it is transported to uterus by muscular contractions of the fallopian tube and the cilia lining the tube. • Uterus is site of implantation 2- Oocyte in fallopian tube • Oocyte is a haploid cell, containing only 1 copy of each chromosome. • Oocyte remains viable within the fallopian tube for approximately 12 hours. 3- Oocyte and sperm • The oocyte is surrounded by a plasma membrane, a thick extracellular matrix or zona pellucida and additional layers of cells, the corona radiata . Sperm are haploid cells and are attracted to the oocyte. • Sperm enzymatically digest a pathway through these membranes to fertilize the oocyte. • Important that only one sperm fertilizes the oocyte, and all others are inhibited by chemical changes induced in the zona pellucida after the first sperm has entered. 4- Fertilization • Unequal contribution of cytoplasm - small amount of cytoplasm derived from the sperm compared to the enormous amount derived from the oocyte. • Sperm and oocyte contribute equal amounts of genetic material. 5- Zygote is a totipotent cell • After nuclear fusion, the 2 haploid cells fuse into a single diploid cell or zygote . • Many changes occur in order for fertilization to lead to development: Meiosis II is completed. Protein synthesis is stimulated, cytoplasm within the zygote segregates to produce a polarity and DNA replication begins.
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2 6- Two cell stage • 24 hr after fertilization the mammalian zygote begins cleavage , the series of mitotic divisions by which the enormous volume of egg cytoplasm is divided into smaller cells. • Cells formed by this cleavage are called blastomeres. 7- Four to Sixteen cell stage • As cleavage continues, more cells are formed. The zona pellucida continues to surround cells, maintaining a constant diameter of the embryo. • At the 16-32 cell stage, the embryo is called a
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This note was uploaded on 02/03/2010 for the course NEUROSCI 101A taught by Professor Scheibell during the Winter '10 term at UCLA.

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Lect 1 Student notes 09 - BASIC EMBRYOLOGY Chapter 3 Dr...

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