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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 April 4, 2014

 

"Postmortem autistic brain tissue revealed patch-like areas of disorganized neurons.
Arrows show a patch of decreased or absent expression of genetic markers across
multiple layers of the dorsolateral prefrontal cortex."

Image Credit: Rich Stoner, Ph.D., University of California, San Diego

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Disorganized neocortex origin of autism?

The architecture of the autistic brain is speckled with regions of incomplete cortical brain, according to new research.

Published in the New England Journal of Medicine, this study suggests that brain irregularities in children with autism can be traced back to prenatal development.


"While autism is generally considered a developmental brain disorder, research has not identified a consistent or causative lesion.

"If this new report of disorganized architecture in the brains of some children with autism is replicated, we can presume this reflects a process occurring long before birth. This reinforces the importance of early identification and intervention."

Thomas R. Insel, M.D., director of NIMH.


Eric Courchesne, Ph.D. along with Rich Stoner, Ph.D., of the Autism Center of Excellence at the University of California, San Diego and colleagues in the Allen Institute for Brain Science, investigated the brain's cellular architecture in children with autism. They focused on the brain's outermost layer called the cerebral cortex. Courchesne found an overabundance of neurons in the prefrontal cortex of children with autism.

For the current study, the researchers analyzed gene expression in postmortem brain tissue from children with and without autism, all between the ages of  2 and 15 years.

As the prenatal brain develops, neurons in the cortex differentiate into six layers. Each layer is composed of brain cells with specific patterns of connections. In their research, the team looked for genes that serve as cell markers for each of these cortical layers, as well as for genes associated with autism.


Scientists found that markers defining layers of the cortex were absent in 91 percent of autistic brains, but missing in only 9 percent of control brains.

The disorganized cortical patches stretched 5-7 millimeters (0.20-0.28 inches), enclosing multiple brain layers. The regions affected are known for mediating social skills including language, emotion and communication, which with deficits are all hallmarks of autism.

Researchers therefore conclude that disorganization in these specific cortical regions may reflect the severity of symptoms an autistic child experiences.


According to the research, as the faulty cell layering does not occur over the entire cortex, the developing brain may have a chance to rewire its connections by sidestepping the pathological patches and recruiting cells from neighboring brain regions to assume critical roles in social and communication function.

BACKGROUND
Autism involves early brain overgrowth and dysfunction, which is most strongly evident in the prefrontal cortex. As assessed on pathological analysis, an excess of neurons in the prefrontal cortex among children with autism signals a disturbance in prenatal development and may be concomitant with abnormal cell type and laminar development.

METHODS
To systematically examine neocortical architecture during the early years after the onset of autism, we used RNA in situ hybridization with a panel of layer- and cell-type–specific molecular markers to phenotype cortical microstructure. We assayed markers for neurons and glia, along with genes that have been implicated in the risk of autism, in prefrontal, temporal, and occipital neocortical tissue from postmortem samples obtained from children with autism and unaffected children between the ages of 2 and 15 years.

RESULTS
We observed focal patches of abnormal laminar cytoarchitecture and cortical disorganization of neurons, but not glia, in prefrontal and temporal cortical tissue from 10 of 11 children with autism and from 1 of 11 unaffected children. We observed heterogeneity between cases with respect to cell types that were most abnormal in the patches and the layers that were most affected by the pathological features. No cortical layer was uniformly spared, with the clearest signs of abnormal expression in layers 4 and 5. Three-dimensional reconstruction of layer markers confirmed the focal geometry and size of patches.

CONCLUSIONS
In this small, explorative study, we found focal disruption of cortical laminar architecture in the cortexes of a majority of young children with autism. Our data support a probable dysregulation of layer formation and layer-specific neuronal differentiation at prenatal developmental stages. (Funded by the Simons Foundation and others.)

Reference: Patches of disorganization in the neocortex of children with autism. Stoner R, Chow ML, Boyle MP, Sunkin SM, Mouton PR, Roy S, Wynshaw-Boris A, Colamarino SA, Lein ES, Courchesne E. NEJM, March 27, 2014.

About the National Institute of Mental Health (NIMH): The mission of the NIMH is to transform the understanding and treatment of mental illnesses through basic and clinical research, paving the way for prevention, recovery and care.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases.