K12 Comparative Embryology
Introduction
All human and animal embryos go through very similar stages of early development. The major difference appears to be how long it takes to reach each of these same stages. We now also know that many of the underlying signals that regulate development are the same between these different species.
This page will introduce how we can compare the development of different animal embryos.
Human Carnegie Stages
Carnegie stages are named after the famous USA institute which began collecting and classifying embryos in the early 1900's. Human stages are based on the external and/or internal features of the embryo, and are not directly dependent on either age or size. The human embryonic period proper is divided into 23 Carnegie stages covering the first 8 weeks after fertilisation (post-ovulation). Other features used in this classification include: ranges of age in days, number of segments (somites) present, and embryonic size.
Embryonic size is measured by the crown rump lengths (CRL).
- Links: Carnegie Stages
Species Comparison of Carnegie Stages
- Links: Animal Development
Cite this page: Hill, M.A. (2024, March 28) Embryology K12 Comparative Embryology. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_Comparative_Embryology
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G