Carnegie stage 9

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Introduction

Stage9 sem1.jpg

Facts

Human embryonic stage 9 occurs during week 3 between 19 to 21 days.

Gestational Age GA - week 5

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.


Stage 9 Links: Week 3 | Gastrulation | Lecture | Somitogenesis | Lecture - Mesoderm | Lecture - Ectoderm | Lecture - Early Vascular | Science Practical | Carnegie Embryos | Category:Carnegie Stage 9 | Next Stage 10
  Historic Papers: 1920 | 1926 | 1945
Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
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

Summary

  • 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".

See also Events

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


Links: Week 3 | Gastrulation | Lecture | Practical | 1920 Carnegie No.1878 | Stage 10

Bright Field Lateral

Lateral View Ventrolateral View
Stage 9 View 1 Stage 9 View 2
Lateral View 1 - Large | 800px | Medium | Small Ventrolateral View 2 - Large | 800px | Medium | Small

Scanning EM Lateral

Lateral View Ventrolateral View
Stage 9 View 1 Stage 9 View 2
Lateral View 1 - Small | Medium | Large Ventrolateral View 2 - Small | Medium | Large

Notochordal plate

Stage9 sem3c.jpg

Notochordal plate - Small | Medium | Large

Bright Field Dorsal

Dorsal Ventral
Stage 9 View 3 Stage 9 View 4
Lateral View 1 - Small | Medium | Large Ventrolateral View 2 - Small | Medium | Large

Scanning EM Dorsal

Stage9 sem4c.jpg Stage9 sem5c.jpg Stage9 sem6c.jpg Stage9 sem7c.jpg

Kyoto Collection

Dorsal View Ventral View
Stage 9 View 1 Stage 9 View 2
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


Image source: The Kyoto Collection images are reproduced with the permission of Prof. Kohei Shiota and Prof. Shigehito Yamada, 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.

Events

  • hearing - otic placode (disc or otic zone) appears opposite the rhombencefhalic fold.[1][2]


References

Shaner RF. A human embryo of two to three pairs of somites. (1945) Canad. J. Res. 23: 235-243.

Additional Images

Primordial germ cell region

Light Images

Scanning EM Images

SEM Dorsal

SEM Cranial Neural fold

SEM Caudal Region

SEM Caudal Region cross section

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

Historic Images

Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

1920 Carnegie No.1878 A Human Embryo at the Beginning of Segmentation, with Special Reference to the Vascular System. By N. William Ingalls

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, March 28) Embryology Carnegie stage 9. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_stage_9

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