Welcome to The Visible Embryo

Home-- -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- -Contact
 

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!



Home

History

Bibliography

Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System

Contact The Visible Embryo

News Alerts Archive

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.
Content protected under a Creative Commons License.

No dirivative works may be made or used for commercial purposes.

Return To Top Of Page
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
Google Search artcles published since 2007
 
 

Home | Pregnancy Timeline | News Alerts | News Archive July 5, 2013

 
The Human Heart

Blood flows through the heart in one direction, from the atria to the ventricle ,
and out of the great arteries, or the aorta for example. Blood is prevented from
flowing backwards by the tricuspid, bicuspid, aortic, and pulmonary valves.

The heart acts as a double pump. The function of the right side of the heart
(see right heart) is to collect de-oxygenated blood, in the right atrium, from the
body (via superior and inferior vena cavae) and pump it, via the right
ventricle, into the lungs (pulmonary circulation) so that carbon dioxide
can be dropped off and oxygen picked up (gas exchange).
This happens through the passive process of diffusion.

The left side (see left heart) collects oxygenated blood from the lungs
into the left atrium. From the left atrium the blood moves to the left ventricle
which pumps it out to the body (via the aorta).atien






WHO Child Growth Charts

 

 

 

Scientists identify molecular switch that kick starts formation of arteries

The findings reveal underlying events that distinguish arteries from veins. Precisely what drives this commitment, which is essential for shaping cardiovascular development, has long eluded researchers. Now, scientists at the Gladstone Institutes have identified the molecular signals that direct this process. In so doing, they illustrate how even the most complex of biological systems can be directed by the most subtle shifts in molecular signaling.

The ability to form blood vessels is one of evolution’s crowning achievements, and something that separates vertebrates (animals with a backbone) from the rest of the animal kingdom. The two types of blood vessels, arteries and veins, are formed from the same precursor cell type—endothelial cells—that become committed to an arterial or venous cell fate during embryonic development.

In the latest issue of Developmental Cell, researchers in the laboratory of Gladstone Senior Investigator Benoit Bruneau, PhD, describe the precise order and timing of signals that spur the formation of arteries. Specifically, they piece together a molecular signaling pathway by which a protein called vascular endothelial growth factor (Vegf) directs the activation of Delta-like 4 (Dll4), which is critical to artery formation.

Arteries and veins each have different identities and distinct functions. Arteries carry oxygenated blood from the heart out to tissues, while veins carry unoxygenated blood back to the heart. Understanding how arteries are made at the molecular level—and specifically how they differ from veins—is important not only for understanding diseases in which arteries and veins connect abnormally, but also to inform strategies for making new arteries, which could prove invaluable for treating coronary artery disease.


The key to this understanding lies with Dll4, one of the earliest known genes involved in artery formation. In fact, scientists currently use Dll4 as a marker to identify which cells will grow and differentiate into arteries, and which will not. Dll4 works by binding to another protein—known as Notch—which in turn promotes artery formation.

But there is a third player in this process: Vegf. It is secreted from cells in the embryo, which among other things activates Dll4. But exactly how Dll4, Notch and Vegf all work in concert to transform early embryonic cells into cells that form arteries has stumped researchers.


“We knew that Dll4, when activated, directs artery formation, but couldn’t pinpoint how it is activated in the first place,” said Dr. Bruneau, who is also a professor of pediatrics at the University of California, San Francisco, with which Gladstone is affiliated. “Here, we’ve mapped the series of steps that precede Dll4 activation and that set the stage for the formation of arteries—shedding light into a so-called ‘black box’ of embryonic development.”

In this study, the team delved deep into the nucleus of cells belonging to mouse and zebrafish embryos—two important animal models of embryonic development—in order to determine how the Dll4 gene is turned on. They used sophisticated molecular biology approaches, together with experiments that deleted specific genes from the animal models, to fill in the steps that led from Vegf signaling to Dll4 activation. And what they found was surprising.

“Vegf sets off a signaling cascade that eventually activates a group of proteins, called Mitogen Activated Protein Kinases, or MAPKs,” said Gladstone Staff Scientist Joshua Wythe, PhD, the paper’s lead author. “This, in turn, activates another group of proteins, called ETS transcription factors, and it is this signaling relay—from Vegf to MAPKs to ETS factors—that turns on an maintains Dll4 activity, helping the arterial cells grow and gain their cellular identity over time.”

In biology, a signaling cascade is a series of chain reactions that help cells amplify a particular signal—like a domino effect. Here, the research team identified Vegf as being the first domino, followed by the activation of MAPKs, then ETS factors and so on.

“Interestingly, the ETS factors aren’t specific to soon-to-be arterial cells, but rather they are present throughout the embryo,” explained Jason Fish, PhD, a former Gladstone postdoctoral fellow, now at the University of Toronto, who collaborated with the Gladstone team. “Instead, the Vegf signaling cascade alerts only those MAPKs and ETS factors within the realm of Dll4—assuring only the correct cells grow and differentiate over time to form arteries.”

This research is important not only because it uncovers the molecular link between Vegf and Dll4, but also because it shows how signaling cascades like this one can direct genes—which are normally active throughout the embryo—to perform tasks only in specific cell types.

“In the future we will refine our approach to see whether this signaling cascade regulates other arterial genes in the developing embryo,” said Dr. Bruneau. “We hope this research will help inform clinicians into congenital defects related to the formation and maintenance of arteries and veins, and may also yield new strategies that can coax the development of arteries from stem cells—which may prove useful for treating coronary artery disease.”

Research Scientist W. Patrick Devine, MD, PhD, and Research Associate Daniel He also participated in this research at Gladstone, which was supported by the American Heart Association, the California Institute of Regenerative Medicine, the DeGeorge Charitable Trust, the William H. Younger, Jr., Foundation and the National Institutes of Health.

About the Gladstone Institutes
Gladstone is an independent and nonprofit biomedical-research organization dedicated to accelerating the pace of scientific discovery and innovation to prevent, treat and cure cardiovascular, viral and neurological diseases. Gladstone is affiliated with the University of California, San Francisco.

Original press release:http://www.gladstoneinstitutes.org/pressrelease/2013-07-03/gladstone-scientists-identify-molecular-switch-that-kick-starts-formation-of: