Carnegie stage 9
From Embryology
Contents |
Introduction
Facts
Human embryonic stage 9 occurs during week 3 between 19 to 21 days.
The embryo is now 1.5 to 2.5 mm in size and somites have begun to form and number between 1 to 3 somite pairs during this stage.
The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images.
See also Carnegie stage 9 image gallery.
Events
Ectoderm - Neural plate brain region continues to expand, neural plate begins folding over the notochord. Gastrulation continues through the primitive streak region.
Mesoderm - Paraxial mesoderm segmentation into somites begins (1 - 3 somite pairs). Lateral plate mesoderm begins to vacuolate, dividing it into somatic and splanchnic mesoderm and to later form the intra-embryonic coelom. Prechordal splanchnic mesoderm begins to form the cardiogenic region, from which the primordial heart will develop.
Endoderm - Notochordal plate still visible which will form the notochord. Endoderm is still widely open to the yolk sac and germ cells form part of this layer. Extra-embryonic mesoderm on the yolk sac surface begins to form "blood islands".
Identify
- Neural groove and neural folds, the mesoderm, which segments beside the neural groove to form somites but extends laterally to margin of embryonic disc lateral plate mesoderm, where it merges with the covering extraembryonic mesoderm.
- The intra-embryonic coelom develops in the middle of the lateral plate mesoderm. Note amniotic ectoderm covered by extra-emebryonic mesoderm (empty spaces above and below the mesoderm are artefacts, as are the lateral folds in the ectoderm).
The first two images using bright field microscopy approximate the orientation of the scanning electron micrographs below. There are additional scanning electron micrographs showing selected features in detail. Carnegie_stage_9 image gallery
Carnegie Stages
1 | 3 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Carnegie Stages
Bright Field Lateral
| Lateral View | Ventrolateral View |
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| Lateral View 1 - Small | Medium | Large | Ventrolateral View 2 - Small | Medium | Large |
Scanning EM Lateral
| Lateral View | Ventrolateral View |
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| Lateral View 1 - Small | Medium | Large | Ventrolateral View 2 - Small | Medium | Large |
Notochordal plate
Notochordal plate - Small | Medium | Large
Bright Field Dorsal
| Dorsal View 1 | Dorsal View 2 |
|---|---|
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| Lateral View 1 - Small | Medium | Large | Ventrolateral View 2 - Small | Medium | Large |
Scanning EM Dorsal
Kyoto Collection
| Dorsal View | Ventral View |
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| Embryonic disc, showing the epiblast viewed from the amniotic (dorsal) side. | Embryonic disc, showing the epiblast, connecting stalk and brain fold. |
Image source: UNSW Embryology page Created: 19.03.1999
Carnegie Stages
1 | 3 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Carnegie Stages
Image Source: Scanning electron micrographs of the Carnegie stages of the early human embryos are reproduced with the permission of Prof Kathy Sulik, Department of Cell & Developmental Biology, The University of North Carolina. Images are for educational purposes only and cannot be reproduced electronically or in writing without permission. Embryonic Development
Image source: The Kyoto Collection images are reproduced with the permission of Prof. Kohei Shiota, Anatomy and Developmental Biology, Kyoto University Graduate School of Medicine, Kyoto, Japan for educational purposes only and cannot be reproduced electronically or in writing without permission.
- Dr Mark Hill 2009, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
