File:Stage8 SEM1.jpg

From Embryology

Stage8_SEM1.jpg(257 × 450 pixels, file size: 25 KB, MIME type: image/jpeg)

Human Embryo (Carnegie stage 8)

Scanning electron micrograph.

Features: neural plate, brain fold, neural groove, amniotic sac, presomitic mesoderm, embryonic disc, primitive node, primative streak, primative groove, connecting stalk

Facts: Week 3, 17 - 19 days, 1.0 - 1.5 mm

View: embryonic disc, showing the epiblast viewed from the amniotic (dorsal) side. Amniotic membrane removed, brain fold top and connecting stalk bottom.

Events: Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.

Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.

From the primitive node a tube extends under the ectoderm in the opposite direction to the primitive streak. This tube forms first the axial process then notochordal process, then finally the notochord.

The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract.


Links: Carnegie stage 8


Image Source: Scanning electron micrographs of the Carnegie stages of the early human embryos are reproduced with the permission of Prof Kathy Sulik, from embryos collected by Dr. Vekemans and Tania Attié-Bitach. Images are for educational purposes only and cannot be reproduced electronically or in writing without permission.

Embryonic Development

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

Cite this page: Hill, M.A. (2024, May 19) Embryology Stage8 SEM1.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Stage8_SEM1.jpg

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

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current22:30, 3 August 2009Thumbnail for version as of 22:30, 3 August 2009257 × 450 (25 KB)S8600021 (talk | contribs)Human embryo (Carnegie stage 8) scanning electron micrograph Features: brain fold, neural groove, amniotic sac, presomitic mesoderm, embryonic disc, primitive node, primative streak, primative groove, connecting stalk Facts: Week 3, 17 - 19 days, 1.0 -