UNSW Embryology

Beginnings, Growth and Development

© Dr Mark Hill (2008)

Acknowledgements

Practical 6 - Embryonic Development

Introduction

The first Embryology practical covered gametogenesis, fertilization, implantation and early events of embryonic development. The third week is the begining of the embryonic period which continues through to week eight. Stages are based on the external and/or internal morphological development of the vertebrate embryo, and are not directly dependent on either age or size. The human embryonic period proper is divided into 23 Carnegie stages. Criteria beyond morphological features include age in days, number of somites present, and embryonic length. These stages are also shown in the movie "Carnegie stage human growth through embryonic period" below.

Staging can be applied to all vertebrates, and most vertebrate embryos develop during the embryonic period in much the same way, we can directly compare the timing of development for different species. From the Carnegie stage comparison table you can see that to reach the end of embryonic development Carnegie stage 23 can take from as little as 10 days in chickens to nearly 60 days in humans. During this Embryonic period within the embryo: axes are established, the embryo folds and early organogenesis occurs. Outside the embryo: the placentata develops from chorionic villi and the fetal mebranes grow (Practical 8). The third Practical (week 11) continue through the late Embryonic to Fetal period (week 9 onward).

Exercises

This period of development is complex, and an entire class could be spent on folding or development of any one organ system. Therefore the Lab must be reasonably general when covering organogenesis, organ/system development.

We will also be using the Carnegie stage 7-23 images to examine external changes on the embryo. Identify the key structures in Figures on the following pages and discuss as a small group the dynamic events of development that are occurring at this early stage. If required ask your tutor for assistance. For new terms use the glossary link found at the bottom of each page.

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Quick Links

Glossary

Comments

Practical notes and content are under development for this current year 2008, please let me know of links/images etc that do not function. This second embryology practical will continue on from implantation to cover the Embryonic period of development. This period of development is complex, and an entire class could be spent on folding or development of any one organ system. Therefore the Lab must be reasonably general in covering the details of folding and organogenesis. If you are interested in a more detailed coverage, look at the Carnegie and Systems sections of Notes (from the lefthand menu). The lefthand side menu has links to all pages required for this Lab. Also at the bottom of the same menu is a window to Search UNSW Embryology using any term/concept you do not understand. (note the search window uses Google, so will only work with an active internet connection. The Kyoto Collection images are reproduced with the permission of Prof. Kohei Shiota for tutorial/revision purposes and cannot be reproduced electronically or in writing without permission. Thanks also to the late Prof William Larsen, for allowing use of movies based on his excellent Textbook.

These notes and linked materials have been prepared for Educational purposes only.

Please email Dr Mark Hill if you wish to make a comment about this current project.

UNSW Embryology ISBN: 978 0 7334 2609 4

UNSW CRICOS Provider Code No. 00098G