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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive Aug 22, 2013


Radix balthica, the common pond snai.

Image credit: Wikimedia

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The timing and sequence of development is heritable

Scientists using a pioneering bio-imaging system to record simultaneously the development of hundreds of aquatic embryos have discovered significant parent-offspring similarities in the timing and sequence of that development.

Researchers at Plymouth University, United Kingdom, have found the timing of key developmental milestones – such as the first beating of the heart, formation of the eyes and movement – differs markedly between individuals in a species of aquatic snail, but also that these timings appear to be heritable, i.e. they are passed from mother to offspring.

The study, made possible by a home-built piece of technology combining a high depth of focus lens more commonly found in aviation safety, a shutterless digital camera, and a robotic microscope stage, sheds new light on the relationship between development and evolution. It is being published in the Royal Society journal Proceedings of the Royal Society B on Wednesday 21st August.

The research, carried out in the Marine Biological and Ecology Research Centre, has taken place over the past four years as scientists carefully constructed and refined their imaging set up.

"The link between development and evolution has remained one of the key questions in biology. Science has long suspected that heterochrony – the altered timing of developmental events between ancestors and descendants – could be the main driver of evolutionary change, but studies have primarily focused on the differences in developmental events between species with the assumption that within species variation is negligible.

What we have been able to do is bring to light the astounding variation within species and show that event timing during early development is heritable."

Dr Oliver Tills, project leader,

Snail embryos were placed in tiny little aquaria and their development recorded in high definition three-dimensional detail using time lapse photography. The bio-imaging setup enabled the team to pinpoint changes in the animal right through its body, so that they could record the precise timings of 12 key developmental milestones such as the formation of the eyes, of the shell, and hatching, spread throughout its two week embryonic development.

The team discovered marked similarities between a parent and its offspring in all 12 developmental events studied, and in two of these events – foot attachment (the transition from gliding around the egg using tiny hairs, to attaching to the inside of the egg using its muscular foot) and crawling (the same behaviour you see in an adult snail) – the strength of this similarity was sufficiently strong that it indicated heritability.

Dr Simon Rundle, Associate Professor in Freshwater Ecology, said: "There was clear evidence of similarities in the timing of all 12 physiological and morphological developmental events between parents and offspring, and of heritability in the timing of foot attachment and crawling."

Professor John Spicer, also of Plymouth University, added: "These results challenge how we understand the interaction between development and evolution. They shed light on the potential origins of a pervasive feature in evolution – the difference in the timing of developmental events which is so evident between species. And that's exciting."

The research team, part of the University's Faculty of Science and Environment, and its Marine Institute, took the decision to build the unique device after they approached some of the world's leading lens-makers and microscope manufacturers, only to be told that nothing existed that could do what they wanted. The device they've created has a range of between 20 to 10,000 times magnification, and can be used to study the development of species ranging from single-cell organisms to zebrafish, with up to 384 specimens in separate little aquaria at any one time.

Understanding the link between ontogeny (development) and phylogeny (evolution) remains a key aim of biology. Heterochrony, the altered timing of developmental events between ancestors and descendants, could be such a link although the processes responsible for producing heterochrony, widely viewed as an interspecific phenomenon, are still unclear. However, intraspecific variation in developmental event timing, if heritable, could provide the raw material from which heterochronies originate. To date, however, heritable developmental event timing has not been demonstrated, although recent work did suggest a genetic basis for intraspecific differences in event timing in the embryonic development of the pond snail, Radix balthica. Consequently, here we used high-resolution (temporal and spatial) imaging of the entire embryonic development of R. balthica to perform a parent–offspring comparison of the timing of twelve, physiological and morphological developmental events. Between-parent differences in the timing of all events were good predictors of such timing differences between their offspring, and heritability was demonstrated for two of these events (foot attachment and crawling). Such heritable intraspecific variation in developmental event timing could be the raw material for speciation events, providing a fundamental link between ontogeny and phylogeny, via heterochrony.

About Plymouth University
Consistently ranked as one of the leading universities in the UK, and awarded a Queen's Anniversary Prize for Higher and Further Education in 2012, Plymouth has a strong record of excellence, enterprise and innovation across its teaching and research activities. Distinguished by its long-term engagement with business and the community, the University enjoys outstanding links with employers and plays a key role in civic and regional leadership. It is the only university in the world to have been awarded the Social Enterprise Mark in recognition of its work in support of the sector.

With around 30,000 students, including those studying higher education at its partner colleges throughout the South West, the University is one of largest in the UK. It enjoys a high rate of graduate employment and has recently invested more than £150 million in its estate and facilities to enhance the student experience and support world-class research.

Plymouth has embedded sustainability across its operations, and is the overall best performing university in the People & Planet Green League. It is the first modern university to found a medical and dental school – the Plymouth University Peninsula Schools of Medicine and Dentistry – and is the leading provider of Higher Education in Cornwall. For more information, please visit http://www.plymouth.ac.uk

Original press release: http://www.wistar.org/news-and-media/press-releases/wistar-scientists-decipher-structure-nata-enzyme-complex-modifies-most