Week 1
Introduction
Key Events of Human Development during the first week (week 1) following fertilization or Clinical week 3 (LMP).
Links: 2009 Lecture - Fertilization | 2009 Lecture - Week 1 and 2 | Oocyte | Spermatozoa | Fertilization
Human-oocyte to blastocyst
Event | ||
Secretory PhaseStage 1 | Fertilization, Secretory Phase | |
Stage 2 | Morula, Blastula | |
Stage 3 | Blastocyst Hatching (zona pellucida lost) | |
Blastocyst (free floating) | ||
Stage 4 | Adplantation | |
Stage 5 | File:2ndwk.jpg |
Week 1 Movies
Ovulation | Fertilization | Pronuclear Fusion | Week 1 | Ovulation in the rabbit | Fertilization in the mouse |
Week 1 Abnormalities
Dizygotic Twinning
Dizygotic twins (fraternal, non-identical) arise from separate fertilization events involving two separate oocyte (egg, ova) and spermatozoa (sperm).
Monoygotic Twinning
Monoygotic twins (identical) produced from a single fertilization event (one fertilised egg and a single spermatazoa, form a single zygote), these twins therefore share the same genetic makeup. Occurs in approximately 3-5 per 1000 pregnancies, more commonly with aged mothers. The later the twinning event, the less common are initially separate placental membranes and finally resulting in conjoined twins.
Table based upon: Twinning. Hall JG. Lancet. 2003 Aug 30;362(9385):735-43. Review. PMID: 12957099
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Glossary Links
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Cite this page: Hill, M.A. (2024, June 15) Embryology Week 1. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_1
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G