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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.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




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Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.
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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 Dec 20, 2013


This image illustrates the brain connections for one of the subjects, a 4-year-old male
where the colours represent the local directions of a fibre tract
(blue: top-bottom axis; green: front-back axis; red: left-right axis). 

Image Credit: Marcus Kaiser and Sol Lim laboratory, Newcastle University


WHO Child Growth Charts




Brain connections may explain why girls mature faster

Our brain re-organises connections throughout our life. The process begins earlier in girls — which may explain why girls mature faster than boys during the teenage years.

As we grow older, our brains undergo a major reorganisation reducing many connections in the brain. Studying people up to the age of 40, scientists led by Dr. Marcus Kaiser and Ms. Sol Lim at Newcastle University found that while overall connections in the brain get streamlined, long-distance connections — crucial for integrating information — are preserved.

The researchers suspect this newly-discovered selective process might explain why brain function does not deteriorate – and indeed improves – during pruning of the network.

Interestingly, they also found that these changes occurred earlier in females than in males.

The work is published in Cerebral Cortex.

“Long-distance connections are difficult to establish and maintain — but are crucial to fast and efficient processing. If you think about a social network, nearby friends might give you very similar information – you might hear the same news from different people. People from different cities or countries are more likely to give you novel information.

"In the same way, some information flow within a brain module might be redundant whereas information from other modules, say integrating the optical information about a face with the acoustic information of a voice, is vital to making sense of the outside world.”

Dr Marcus Kaiser, reader in neuroinformatics, Newcastle University, United Kingdom

The researchers at Newcastle, Glasgow and Seoul Universities evaluated the scans of 121 healthy participants between the ages of 4 and 40 years — a period of major connectivity changes reflecting maturation of the brain. The work is part of the EPSRC-funded Human Green Brain project which examines human brain development.

To capture nerve fibre change, the researchers used a non-invasive technique called diffusion tensor imaging, a special measurement protocol for Magnetic Resonance Imaging (MRI) scanners.

They found not all long-range connections between brain regions are affected equally. Projections that are preserved are short-cuts quickly linking different processing modules, such as vision and sound.

Disruptions in such connections can be found in many developmental brain disorders such as autism, epilepsy and schizophrenia.

Researchers demonstrated for the first time that the loss of white matter fibres between brain regions is a highly selective process – a phenomenon they call "preferential detachment." They also found fewer connections were lost between distant brain regions, brain hemispheres, and processing modules than expected. This helps explain how we retain a stable brain network during our long period of brain maturation.

Commenting on the loss of brain connections, Ms. Sol Lim adds: “The loss of connectivity during brain development can actually help improve brain function by increasing efficiency. Instead of talking to many people at random, asking a couple of people who have lived in the area for a long time is more efficient to finding your way. In a similar way, reducing projections in the brain brings focus to essential information.”

Academic paper: Preferential Detachment During Human Brain Development: Age- and Sex-Specific Structural Connectivity in Diffusion Tensor Imaging (DTI) Data. Sol Lim; Cheol E. Han; Peter J. Uhlhaas; Marcus Kaiser.Cerebral Cortex 2013; doi: 10.1093/cercor/bht333

Human brain maturation is characterized by the prolonged development of structural and functional properties of large-scale networks that extends into adulthood. However, it is not clearly understood which features change and which remain stable over time. Here, we examined structural connectivity based on diffusion tensor imaging (DTI) in 121 participants between 4 and 40 years of age. DTI data were analyzed for small-world parameters, modularity, and the number of fiber tracts at the level of streamlines. First, our findings showed that the number of fiber tracts, small-world topology, and modular organization remained largely stable despite a substantial overall decrease in the number of streamlines with age. Second, this decrease mainly affected fiber tracts that had a large number of streamlines, were short, within modules and within hemispheres; such connections were affected significantly more often than would be expected given their number of occurrences in the network. Third, streamline loss occurred earlier in females than in males. In summary, our findings suggest that core properties of structural brain connectivity, such as the small-world and modular organization, remain stable during brain maturation by focusing streamline loss to specific types of fiber tracts.