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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 in 1993 as a first generation internet teaching tool consolidating human embryology teaching for first year medical students.

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 SemestersFemale Reproductive SystemFertilizationThe Appearance of SomitesFirst TrimesterSecond TrimesterThird TrimesterFetal 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 HemispheresEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterDevelopmental Timeline
Click weeks 0 - 40 and follow fetal growth
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November 30, 2012--------News Archive Return to: News Alerts


Findings Could Advance Treatments for Spinal Cord Injuries, ALS








WHO Child Growth Charts

       

Scientists Describe Genetic Signature Of A Vital Set Of Neurons

Scientists have identified two genes involved in establishing the neuronal circuits required for breathing

The scientists at the NYU Langone Medical Center reported their findings in a study published in the December, 2012 issue of Nature Neuroscience.

The discovery, featured on the journal’s cover, could help advance treatments for spinal cord injuries and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), which gradually kill neurons that control the movement of muscles needed to breathe, move, and eat.


The study identifies a molecular code
that distinguishes a group of muscle-controlling
nerve cells collectively known as the
phrenic motor column (PMC).


These cells lie about halfway up the back of the neck, just above the fourth cervical vertebra, and are “probably the most important motor neurons in your body,” says Jeremy Dasen, PhD, assistant professor of physiology and neuroscience and a member of the Howard Hughes Medical Institute, who led the three-year study with Polyxeni Philippidou, PhD, a postdoctoral fellow.


Harming the part of the spinal cord where the
PMC resides can instantly shut down breathing.

But relatively little is known about what
distinguishes PMC neurons from neighboring
neurons, and how PMC neurons develop
and wire themselves to the diaphragm in the fetus.


The PMC cells relay a constant flow of electrochemical signals down their bundled axons and onto the diaphragm muscles, allowing the lungs to expand and relax in the natural rhythm of breathing.

Dr. Dasen:“We now have a set of molecular markers that distinguish those cells from other populations of motor neurons, so that we can study them in detail and look for ways to selectively enhance their survival.”

Degeneration of PMC neurons is the primary cause of death in patients with ALS and spinal cord injuries.

To find out what distinguishes PMC neurons from their spinal neighbors in mice, Dr. Philippidou injected a retrograde fluorescent tracer into the phrenic nerve, which wires the PMC to the diaphragm, and then looked for the spinal neurons that lit up as the tracer worked its way back to the PMC. He used transgenic mice that express green fluorescent protein (GFP) in motor neurons and their axons in order to see the phrenic nerve.

After noting the characteristic gene expression pattern of these PMC neurons, Dr. Philippidou began to determine their specific roles. A complicated strain of transgenic mice, based partly on mice supplied by collaborator Lucie Jeannotte, PhD, at the University of Laval in Quebec, ultimately revealed two genes, Hoxa5 and Hoxc5, as the prime controllers of proper PMC development. Hox genes (39 are expressed in humans) are well known as master gene regulators of animal development.


When Hoxa5 and Hoxc5 are silenced in mice
embryonic motor neurons, PMC fails to form
its usual, tightly columnar organization and doesn’t
connect correctly to the diaphragm, leaving a
newborn animal unable to breathe.

“Even if you delete these genes late in fetal
development, the PMC neuron population
drops and the phrenic nerve doesn’t form
enough branches on diaphragm muscles.”

Jeremy Dasen, PhD
assistant professor of physiology and neuroscience,
member of the Howard Hughes Medical Institute


Dr. Dasen plans to use the findings to help understand the wider circuitry of breathing—including rhythm-generating neurons in the brain stem, which are in turn responsive to carbon dioxide levels, stress, and other environmental factors. “Now that we know something about PMC cells, we can work our way through the broader circuit, to try to figure out how all those connections are established,” he says.

“Once we understand how the respiratory network is wired we can begin to develop novel treatment options for breathing disorders such as sleep apneas,” adds Dr. Philippidou.

In late October Dr. Dasen lost many of his transgenic mice when Hurricane Sandy flooded the basement of the Smilow building at NYU Langone Medical Center. But just before the hurricane hit, he sent an important group of these mice back to Dr. Jeannotte in Quebec, “so we didn’t lose everything,” he says.

A commentary about the study appears in the issue at http://www.nature.com/neuro/journal/v15/n12/full/nn.3272.html

Original article: http://communications.med.nyu.edu/media-relations/news/scientists-describe-genetic-signature-vital-set-neurons