Models of Human Development
|Embryology - 20 Jun 2021 Expand to Translate|
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There are many research animal species that have been used as models of development. The embryonic development of different species can also be classified by the same Carnegie stage system.
It should be noted that there are some specific differences in some of these model species when compared to human development.
|Animal Development: axolotl | bat | cat | chicken | cow | dog | dolphin | echidna | fly | frog | goat | grasshopper | guinea pig | hamster | horse | kangaroo | koala | lizard | medaka | mouse | opossum | pig | platypus | rabbit | rat | sea squirt | sea urchin | sheep | worm | zebrafish | life cycles | development timetable | development models | K12|
Species Comparison Timeline
|Note these Carnegie stages are only approximate day timings for average of embryos. Links: Carnegie Stage Comparison|
|Postnatal Animal Models||mouse||rat||pig|
|Pregnancy period (days)||18 – 21||21 – 23||110 – 118|
|Placenta type||Discoidal, decidual
|Litter size||6 – 12||6 – 15||11 – 16|
|Birth weight (g)||0.5 – 1.5||3 – 5||900 – 1600|
|Weaning weight male/female (g)||18 – 25/16 – 25||55 – 90/45 – 80||6000 – 8000|
|Suckling period (days)||21–28||21||28–49|
|Solid diet beginning (days)||10||12||12 – 15|
|Puberty male/female (week)||4 – 6/5||6/6 – 8||20 – 28|
|Life expectancy (years)||1 - 2||2 - 3||14 – 18|
|Table data - Otis and Brent (1954) Links: timeline|
Animal Development Times
|The table below lists the approximate development time for a large number of different animals, ranging from the opossum at 12 days to the elephant at 660 days.
Fly Development - The fruitfly (drosophila) was and is the traditional geneticist's tool. It has been transformed to an magnificent embryologist's tool, with developmental mechanisms being uncovered in this system combined with homolgy gene searches in other species. The fly genome was one of the first to be been completely sequenced. In early development nurse cells sacrifice their cytoplasmic contents to allow egg growth and early pattern formation is through the localization of maternal messenger RNAs (mRNAs).
Guinea Pig Development - The guinea pig has been used as a model animal in many animal model studies; developmental, dietary, tetragenic, including the effects of maternal temperature on development.
|The rabbit along with human, are the few species which show birth defects with thalidomide (teratogenic effects) which were not detected with prior testing on other species.|
|The rat is available as inbred, outbred and mutant strains. They have been generally beaten as a model by their mice brethren, as the molecular tools that became available (stem cells, knockout genes, etc). Rat embryos do have the advantage of being much larger than mouse embryos and easy to breed. Rat development is also generally 1 day behind from mouse.
Zebrafish Development - Zebrafish are seen as the latest and greatest "model' for embryological development studies. They can be easily genetically altered and develop as practically "see through" embryos, all internal development can be clearly observed from the outside in the living embryo.
There are some specific differences in these animal model species when compared to human development. They are listed below in a system by system analysis.
(This section in draft status - notice removed when complete)
Testis Common Location
- abdominal testes - cats, dogs, and horses.
- inguinal testes - rabbits and horses, occasionally in cats and dogs.
- Laboratory animals rarely.
- Cattle or sheep (≤1%).
- Carnegie Stage Comparison - 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. This 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.
- Embryo Staging Systems - 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.
External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.
- National Research Council (US) Committee for the Update of the Guide for the Care and Use of Laboratory Animals. Guide for the Care and Use of Laboratory Animals. 8th edition. Washington (DC): National Academies Press (US); 2011. Bookshelf link
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Cite this page: Hill, M.A. (2021, June 20) Embryology Models of Human Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Models_of_Human_Development
- © Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G