Ebook Medical genetics at a glance (3rd edition): Part 2
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Ebook Medical genetics at a glance (3rd edition): Part 2
Human embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2chard and Bruce R. Kort.106 o 2013 John Wiley & Sons. Ltd. Published 2013 by John Wtey a Sons. Ltd.Figure 415 Time ©cal© of embryogcneoi©OverviewFertilization by a sperm initiates embryogenesis. Mitosis ensues and the pre-emhryo implants in the uterus. Tile embryo proper develops from a few I rile n Ebook Medical genetics at a glance (3rd edition): Part 2ull cells, through creation of three embryonic germ layers. Organogenesis involves interactions between these and is completed by 6 8 weeks, During thEbook Medical genetics at a glance (3rd edition): Part 2
e subsequent period of growth and cylodifferentiittion the individual is called a fetus.The pre-embryo (weeks 0-2)T1k secondary oocyte is shed into thHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2four functions, (Ĩ) stimulation of metaphase II in the secondary oocyte; (ii) restoration of the diploid nuniherof chromosomes; (iii) initiation ọl cleavage', and (iv) determination of sex.Tlie sperm passes through the Coruna cells on die oocyte surface and adheres to the zona pelhicida The acrosoni Ebook Medical genetics at a glance (3rd edition): Part 2e in the spenn head then releases enzymes that digest a tunnel through the zona pclhicida. allowing the sperm Io pass into tile perivitelline space anEbook Medical genetics at a glance (3rd edition): Part 2
d fuse with the oocyte membrane. The sperm head is then engulfed by the oocyte and entry of more sperm prevented by a rapid cortical reaction. The ixxHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2yo is called cleavage and the resultant blastomeres arc smaller after each division. The 16-ccll morula passes down the uterine Illite aided by peristalsis and ciliary movement. A space called the blastoeoel forms oft-ccntic in the morula to create the blastocyst, which swells and bursts from the zo Ebook Medical genetics at a glance (3rd edition): Part 2na pcllucida. T wo different cell types are now recognizable, the flattened trophectodrrm cells of die outer trophoblast and an eccentrically placer!Ebook Medical genetics at a glance (3rd edition): Part 2
inner cell mass or entbry oblast.On day 6 th.' blastocyst implants in the endometrium lining the uterus. Some Iniphiihlasl cells fuse Io form the invaHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2 sinks further into the endometrium.The inner cell mass expired venlrally Io the hlaslocoel Hattens to form the primitive endoderm, or hypoblast, while the remainder forms the primitive ectoderm, or cpiblast. within which develops the amniotic cavity. The double-layered disc called the embryonic dis Ebook Medical genetics at a glance (3rd edition): Part 2c forms from the epiblast and hypoblast at 7-12 days, from which the embryo proper develops.The embryo (weeks 2-8)Gastrulation is the process that creEbook Medical genetics at a glance (3rd edition): Part 2
ates the embryonic mesoderm and initiates activity of lire embryo's own genes. Tile primitive streak first appears in the epiblast al live caudal (taiHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2(head) end of this develops the primitive (or Hensen's) nodeEpiblast cells migrate across the disc, through the primitive groove and into the space above the hypoblast. These become the embryonic mesoderm, creating the three germ fryers: ectodr nil fmm the epiblast, mesoderm, and endoderm from the h Ebook Medical genetics at a glance (3rd edition): Part 2ypoblast together with some epiblast cells that merge with it. Mesoderm cells tltat migrate anteriorly and accumulate in the midiinc form the notochorEbook Medical genetics at a glance (3rd edition): Part 2
dal process, which later extends caudally.The epiblast thickens to form the neural plate and a neural fold arises on either side of the central axis. Human embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2orsal edges of the neural folds are the neural crest cells that migrate out IO give rise to several cell types: nerve, bone, supporting structures of the heart, adrcnalin-sccrcting and pigment cells, etc.As die primitive node moves caudally down die midline, blocks of mesoderm on either side rotate Ebook Medical genetics at a glance (3rd edition): Part 2Io create 42 44 pairs of segmental somites, the most caudal five to seven of which subsequently disappear (sec Chapter 42).The fetus (weeks 8-38)The eEbook Medical genetics at a glance (3rd edition): Part 2
ctoderm is the origin of the miler epithelium arid CNS and. with mesoderm. Ịxrripheral structures such as tile limbs: mestxlenn forms muscles, circulaHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2s of all live major organs are formed through ’inductive’ tissue interactions by about 6 weeks, when the heart Stans beating. Thereafter development mainly involves increase in live number and types of cells.Expected date of delivery (EDD)Birth is generally considered Io occur al 38 weeks from conce Ebook Medical genetics at a glance (3rd edition): Part 2ption, or 40 weeks (280 days) from the first day of the woman’s last nonnal menstrual period (LMP). There are variations among women in cycle length aEbook Medical genetics at a glance (3rd edition): Part 2
nd limes of ovulation, the modal FDD being armind 283 days from the LMP. This has important implications with respect to birth induction: modem practiHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. Pritc Ebook Medical genetics at a glance (3rd edition): Part 2e four paraìơqouữ HOX cluster©Order of expreccton la from the right (3') to left (S') il5XA1------u—y---------u—u---------------------tlry.--r.AA~-----■ ------- -------- -----~-----n-----~-----------------1y AIS All AW A9 KJ Mr An M A3 A2 Al-I-1______________________I-----L,----_-----• ---J-----LJ- Ebook Medical genetics at a glance (3rd edition): Part 2---, ----------------Izj.-r/.-'M------n-----n-----r^Ini ljy [y/ l%. [Jt> li4 ti2 w fWXi- MMMMMD EZZ] — — Oir.i?gis cv C11 a0 CữM r5ÍIÍ7XD —m~ Qir./OfiEbook Medical genetics at a glance (3rd edition): Part 2
dp^ py, 011 p^ pg pftw p3PIFigure 423 Anterior expression limits of the HOX genes in the early CNSFigure 422 Pattern of migration of neural crest cellHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. PritcHuman embryology in outlineFlffire411 Fertilization and implantation (uterus not to «4ile)Medical Geneiics a! a Glance. Third Edition. Dorian J. PritcGọi ngay
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