tailieunhanh - Ebook Medical genetics at a glance (3rd edition): Part 2

(BQ) Part 2 book "Medical genetics at a glance" presents the following contents: Embryology and congenital abnormalities, multifactorial inheritance and twin studies, cancer, biochemical genetics, immunogenetics, molecular diagnosis, genetic counselling, disease management, ethical and social issues. | 41 Human embryology in outline Figure Formation of the embryonic disc Day 9 Amniotic cavity Endometrium Blastocyst cavity Syncytiotrophoblast Day 18 Day 18 Hypoblast primitive endoderm Epiblast primitive ectoderm Cranial end Day 19 Cytotrophoblast Figure Embryonic disc Dorsal view A Primitive node Primitive groove Caudal end i Movement of node A Transverse section along line A-A process A Neural folds Figure Pattern of neural tube closure 21-28 days A Day 20 Neural crests Amniotic cavit Primitive node A A Somites Day 22 A Somite Hypoblast Notochordal process Embryonic disc sagittal section along cranio-caudal axis Neural tube Neural crest cells Epiblast Medical Genetics at a Glance Third Edition. Dorian J. Pritchard and Bruce R. Korf. 106 2013 John Wiley Sons Ltd. Published 2013 by John Wiley Sons Ltd. Figure Time scale of embryogenesis CT Time -2 weeks -14 days 0___T 0 6 2 14 Cleavage Gastrulation 4 28 Organogenesis 6 42 8 56 38 weeks 266 days Somitogenesis Cytodiff erentiation and growth Neurulation Gametes Pre-embryo Embryo Fetus Infant Overview Fertilization by a sperm initiates embryogenesis. Mitosis ensues and the pre-embryo implants in the uterus. The embryo proper develops from a few internal cells through creation of three embryonic germ layers. Organogenesis involves interactions between these and is completed by 6-8 weeks. During the subsequent period of growth and cytodifferentiation the individual is called a fetus. The pre-embryo weeks 0-2 The secondary oocyte is shed into the peritoneal cavity and directed into the adjacent uterine Fallopian tube where fertilization must take place within 24 hours. The sperm performs four functions i stimulation of metaphase II in the secondary oocyte ii restoration of the diploid number of chromosomes iii initiation of cleavage and iv determination of sex. The sperm passes through the corona cells on the oocyte surface and adheres to the zona pellucida. The acrosome in the sperm head then .