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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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Pregnancy Timeline by SemestersDevelopmental TimelineFertilizationFirst TrimesterSecond TrimesterThird TrimesterFirst Thin Layer of Skin AppearsEnd of Embryonic PeriodEnd of Embryonic PeriodFemale Reproductive SystemBeginning Cerebral HemispheresA Four Chambered HeartFirst Detectable Brain WavesThe Appearance of SomitesBasic Brain Structure in PlaceHeartbeat can be detectedHeartbeat can be detectedFinger and toe prints appearFinger and toe prints appearFetal sexual organs visibleBrown fat surrounds lymphatic systemBone marrow starts making blood cellsBone marrow starts making blood cellsInner Ear Bones HardenSensory brain waves begin to activateSensory brain waves begin to activateFetal liver is producing blood cellsBrain convolutions beginBrain convolutions beginImmune system beginningWhite fat begins to be madeHead may position into pelvisWhite fat begins to be madePeriod of rapid brain growthFull TermHead may position into pelvisImmune system beginningLungs begin to produce surfactant
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development


Fetal Timeline      Maternal Timeline      News     News Archive    Aug 14, 2015 

Active labor will dilate the cervix up to 10 centimeters (cm) and last 8 hours and longer.
And labor gets stronger with time - not weaker. Lovingly, the third stage of labor is birth.





How can labor contractions keep growing stronger?

Scientists, for the first time, have identified a mechanism in muscle cells of the uterus that explain how contractions in childbirth grow stronger.

The hormone oxytocin plays a significant role in stimulating uterine contractions. Strong contractions help move a baby down the birth canal. But, what is not known is how contractions keep increasing in strength over the long hours of labor.

A research team at the University of Liverpool Women's Hospital has now investigated how it is possible for uterine contractions to grow stronger when 'biological rules' dictate they should grow weaker. As labor progresses, the tightening uterine muscle squeezes blood vessels, reducing oxygen in the blood, as well as blood flow overall.

"Laboratory tests have shown us that even when the hormone oxytocin is interrupted, surprisingly, uterine muscle carries on contracting — and can grow stronger. This tells us that oxytocin, although significant, is not the only thing contributing to muscle contraction during labor. Prompting us to ask the question - how does this powerful muscle carry on, working against the odds?"

Susan Wray PhD, Professor, Cellular and Molecular Physiology, University of Liverpool; editor-in-chief, Physiological Reports; Director, Centre of Better Births, Liverpool Women's Hospital, University's Institute of Translational Medicine.

Researchers looked for clues in the phenomenon called hypoxic preconditioning found in heart muscle. Hypoxic preconditioning can elicit cellular changes to protect the heart from serious drops in oxygen that are life-threatening. The team found that the uterus reacts to a repetitive lack of oxygen and blood supply, by triggering a previously unidentified process in muscle cells they call Hypoxia-Induced Force Increase (HIFI).

Laboratory experimentation on uterine tissues, revealed that routine contractions subjected to transient dips in oxygen levels (or hypoxia), respond by gradually increasing contraction strength. Once the HIFI mechanism has been triggered — it was sustainable for many hours, just as seen during labor. These results are published in the journal Proceedings of the National Academy of Sciences (PNAS).

"This is an exciting discovery, not only for increasing our general understanding of how biological systems respond to the stress of low oxygen, but also for opening up new research pathways in difficult labors.

"We believe this uterine trigger could be key in resolving issues of prolonged labor, and the increasing number of births ending in emergency caesarean."

Susan Wray PhD

Parturition requires strong uterine contractions. A longstanding enigma has been how contractions strengthen despite also causing transient ischemia as they occlude uterine blood vessels. Here we demonstrate a hitherto undescribed mechanism whereby in an adaptation at labor, brief hypoxia in uterine muscle, stimulates the contractile activity. We have named this hypoxia-induced force increase, or HIFI. We identify the underlying mechanism, which involves adenosine and prostaglandin and a rise in intracellular calcium, and show it is present in animal and human uterus, but only close to delivery. We speculate that aberrations in this powerful mechanism could underlie contractions being triggered too early (preterm labor) or if HIFI is deficient, weak contractions, and thus poor and unsuccessful term labors.

For successful birth, contractions need to become progressively stronger. The underlying mechanisms are unknown, however. We have found that a novel mechanism, hypoxia-induced force increase (HIFI), is switched on selectively, at term, and is essential to strengthening contractions. HIFI is initiated as contractions cyclically reduce blood flow and produce repeated hypoxic stresses, with associated metabolic and transcriptomic changes. The increases in contractility are a long-lasting, oxytocin-independent, intrinsic mechanism present only in the full-term pregnant uterus. HIFI is inhibited by adenosine receptor antagonism and blockade of cyclooxygenase-2 signaling, and partially reproduced by brief episodes of acidic (but not alkalotic) pH. HIFI explains how labor can progress despite paradoxical metabolic challenge, and provides a new mechanistic target for the 1 in 10 women suffering dysfunctional labor because of poor contractions.

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