Embryonic Development: Difference between revisions
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Note that there is variability in the actual timing of specific events and at the end of this period [[Fetal_Development|fetal development]] begins. | Note that there is variability in the actual timing of specific events and at the end of this period [[Fetal_Development|fetal development]] begins. | ||
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! Human Embryo - Australia (NHMRC 2006) | |||
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| Biological definition (NHMRC 2006): | |||
: | :"human embryo means a discrete entity that has arisen from either: | ||
::(a) the first mitotic division when fertilisation of a human oocyte by a human sperm is complete; or | |||
::(b) any other process that initiates organised development of a biological entity with a human nuclear genome or altered human nuclear genome that has the potential to develop up to, or beyond, the stage at which the primitive streak appears; and has not yet reached 8 weeks of development since the first mitotic division." | |||
(More? [https://www.nhmrc.gov.au/_files_nhmrc/file/research/embryos/reports/humanembryo.pdf 2005 NHMRC Discussion paper - biological definition] | PMID 17178746) | |||
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{{Embryo stage movie 1}} | {{Embryo stage movie 1}} |
Revision as of 11:14, 13 November 2015
Embryology - 28 Mar 2024 Expand to Translate |
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Introduction
Author Comments |
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Start here by looking at the external appearance of embryos in sequence from 1 to 23.
It is not so important to memorise the dates, as they are only approximate, but more important to understand growth (size changes) and the development (overall sequence of events) during this period.
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This page shows some key events of human development during the embryonic period of the first eight weeks (weeks 1 - 8) following fertilization. This period is also considered the organogenic period, when most organs within the embryo have begun to form.
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<html5media height="530" width="375">File:Embryo stages 003.mp4</html5media> | Use the above stage number links to images and information about each specific stage of human development over the first 8 weeks. The links below give a broad overview of developmental events during each week.
Alternatively, look through development week by week. |
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
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 |
Week 1
- Week 1 Carnegie stage - 1 | 2 | 3 | 4
- Oocyte | Spermatozoa | Fertilization
- Zygote
- Morula
- Blastocyst
Carnegie stages | |||
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stage 1 | stage 2 | stage 3 | stage 4 |
Week 2
- Week 2 Carnegie stage - 5 | 6
- Trophoblast - outer cell layer
- Embryoblast - inner cell mass
- Implantation
- Bilaminar embryo
Carnegie stages | |
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stage 5 | stage 6 |
Week 3
Carnegie stages | ||
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stage 7 | stage 8 | stage 9 |
Week 4
Carnegie stages | |||
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stage 10 | stage 11 | stage 12 | stage 13 |
Week 5
Carnegie stages | |
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stage 14 | stage 15 |
Week 6
Carnegie stages | |
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stage 16 | stage 17 |
Week 7
Carnegie stages | |
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stage 18 | stage 19 |
Week 8
Carnegie stages | |||
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stage 20 | stage 21 | stage 22 | stage 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
Carnegie Stage Table
Weeks shown in the table below are embryonic post ovulation age, for clinical Gestational Age (GA) measured from last menstrual period, add 2 weeks.
(not to scale) |
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fertilized oocyte, zygote, pronuclei | ||||
morula cell division with reduction in cytoplasmic volume, blastocyst formation of inner and outer cell mass | ||||
loss of zona pellucida, free blastocyst | ||||
attaching blastocyst | ||||
(week 2) |
implantation | |||
extraembryonic mesoderm, primitive streak, gastrulation | ||||
gastrulation, notochordal process | ||||
primitive pit, notochordal canal | ||||
Somitogenesis Somite Number 1 - 3 neural folds, cardiac primordium, head fold | ||||
Somite Number 4 - 12 neural fold fuses | ||||
Somite Number 13 - 20 rostral neuropore closes | ||||
Somite Number 21 - 29 caudal neuropore closes | ||||
Somite Number 30 leg buds, lens placode, pharyngeal arches | ||||
lens pit, optic cup | ||||
lens vesicle, nasal pit, hand plate | ||||
nasal pits moved ventrally, auricular hillocks, foot plate | ||||
finger rays | ||||
ossification commences | ||||
straightening of trunk | ||||
upper limbs longer and bent at elbow | ||||
hands and feet turned inward | ||||
eyelids, external ears | ||||
rounded head, body and limbs | ||||
The embryos shown in the table are from the Kyoto and Carnegie collection and other sources.
Glossary Links
- Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link
Cite this page: Hill, M.A. (2024, March 28) Embryology Embryonic Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Embryonic_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G