Carnegie stage 6

Introduction

Bilaminar embryonic disc

The bilaminar (two layer) embryo is now about 0.2 mm diameter in size. The three extra embryonic spaces (amniotic, yolk sac and chorionic) are present. The large chorionic cavity is surrounded by the cell layers extending to form chorionic villi. These villi are the beginning of the functional units of the placenta. Outside of these villi, and extending from their tips, trophoblasts invade the maternal decidua forming maternal blood-filled lacunae (lakes). Draining into these maternal lacuna empty both uterine glands and spiral arteries that are held open by trophoblast cells. The maternal uterine wall continues to undergo expanding decidualization in response to the implantation process. Facts: Human embryonic stage 6 occurs towards the end of week 2 at approximately 13-14 days. Links: Week 2 | Implantation | Lecture | Practical | Stage 7

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Embryonic Disc	Primitive streak region (gastrulation)
Fully implanted conceptus showing embryonic disc extra-embryonic cavities (amnion, yolk sac and chorion) then chorionic villi and maternal decidua	Detail of embryonic disc (gastrulation) showing extra-embryonic cavities (amnion and yolk sac)

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Glossary Links

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Cite this page: Hill, M.A. (2024, April 20) Embryology Carnegie stage 6. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_stage_6

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G