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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 June 25, 2014

The autonomic nervous system (ANS) regulates internal organs and glands
unconsciously - as in the "fight-or-flight" response - and has three main divisions:
(1) the parasympathetic system (PSNS) stimulates "rest-and-digest" or "feed and breed" activities.
(2) the enteric (gastrointestinal) system, and (3) the parasympathetic nervous system (PSNS).
Sympathetic and parasympathetic nervous responses typically complement each other.
Image source: Wikipedia.org

 






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Unexpected origin for parts of nervous system

A new study shows that the parasympathetic nervous system, is formed differently from what we believed.

Almost all of our body's functions are controlled by an involuntary, autonomous nervous system (ANS) such as the heart, blood vessels, liver and enteric (gastrointestinal) system. At rest, our body is run by energy saving functions regulated by the parasympathetic nervous system (PSNS).

Our current understanding is that cells, including our parasympathetic nerve cells, originate in early progenitor cells which must travel short distances while the embryo is forming. But this old model cannot explain how many organs – which develop relatively late in the growing embryo – are seeded with cells forming the parasympathetic nerves.


This investigation alters a fundamental principal in our understanding of how our peripheral nervous system expands.


Igor Adameyko, department of Physiology and Pharmacology, and Patrik Ernfors, department of Medical Biochemistry and Biophysics, Karolinska Institute, Sweden, began their study by making three-dimensional reconstructions of mouse embryos.

These 3D images recreated how parasympathetic neurons — formed from immature glial cells known as Schwann precursor cells — travel along peripheral nerves to reach their final destinations in body tissues and organs. Immature precursor cells have some of the properties of stem cells and can give rise to several different types of cells — one example being the majority of our pigment cells (melanocytes) originate from Schwann precursor cells, an observation made previously by the same scientists.

Their work is published in the journal Science.


"Our study suggests a new principal in developmental biology, the targeted reassignment of cells in the construction of tissue. Despite the elegance, simplicity and beauty of this principal, it is as yet unclear how Schwann precursor cells are controlled so that only some will be transported and transformed into what becomes the parasympathetic nervous system."

Igor Adameyko, Department of Physiology and Pharmacology, Karolinska Institute, Sweden


Their next hope is that this discovery will open up new ways to treat congenital disorders of the autonomous nervous system through regenerative medicine.

Abstract
The peripheral autonomic nervous system reaches far throughout the body and includes neurons of diverse functions, such as sympathetic and parasympathetic. We show that the parasympathetic system in mice, including trunk ganglia and the cranial ciliary, pterygopalatine, lingual, submandibular and otic ganglia, arise from glial cells in nerves, not neural crest cells. The parasympathetic fate is induced in nerve-associated Schwann cell precursors at distal peripheral sites. We used multicolor Cre-reporter lineage tracing to show that most of these neurons arise from bi-potent progenitors that generate both glia and neurons. This nerve origin places cellular elements for generating parasympathetic neurons in diverse tissues and organs which may enable wiring of the developing parasympathetic nervous system.

Publication: "Parasympathetic neurons originate from nerve-associated peripheral glial progenitors", Vyacheslav Dyachuk, Alessandro Furlan, Maryam Khatibi Shahidi, Marcela, Giovenco, Nina Kaukua, Chrysoula Konstantinidou, Vassilis Pachnis, Fatima Memic, Ulrika Marklund, Thomas Müller, Carmen Birchmeier, Kaj Fried, Patrik Ernfors, and Igor Adameyko, Science online 12 June 2014.

The study has been financed with funds from, among others, the Swedish Research Council, the Swedish Cancer Society, the European Research Council and Hjärnfonden.

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