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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.

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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
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September 17, 2012--------News Archive Return to: News Alerts

The theory of cell death - or apoptosis.
Scientists at CNIO believe that phagocytosis,
the process by which apoptotic
cell particles are ingested (lysis) by macrophage cells and repurposed,
is a result of apoptosis - not a cause for apoptosis.

Cell competition is a mechanism that eliminates slow dividing cells from a growing
cell population. It is believed that the genes wasp, psr, and draper are active in "winner
cells" and are essential for inducing apoptosis and eliminating slower,“loser cells.”

Finally, most of the clearance of the apoptotic debris
is not performed by winner cells but by recruited hemocytes.
Therefore, engulfment is a consequence—not a cause—of loser cells' death.

WHO Child Growth Charts


New Insights On Cell Competition

A research project clarifies how tissues and organs select the 'best' cells for themselves, at the expense of 'loser cells,' (slower cells) who might cause disease

Scientists from the Spanish National Cancer Research Centre (CNIO) describe how natural selection also occurs at the cellular level, and how our body's tissues and organs strive to retain the best cells in their ranks in order to fend off disease processes.

These results appear this week in the new issue of Cell Reports. The research, carried out in the CNIO, is led by Eduardo Moreno, who is currently working at the University of Bern in Switzerland.

Recent studies suggest that natural selection described by
Charles Darwin also occurs at the cellular level,
as our body's tissues and organs strive to retain the best
cells in their ranks in order to fend off disease processes.

Pancreatic cells perform very different functions from skin cells – insulin secretion and barrier protection respectively – even though their genetic material is exactly identical; and this is true of the 200 different cell types that form a human being.

Despite burgeoning interest in the mechanisms of cell competition, which keeps all such functions running smoothly in each body compartment, the exact cellular and molecular mechanisms responsible for maintaining this homeostasis have yet to be established.

Through their studies on fruit flies (Drosophila melanogaster), among the most widely used animal models in research, the authors of the paper have been able to show that cell competition proceeds in various stages.

First, the cells picked as winners for their
superior ability to perform cell functions,
and eliminate the loser cells via
programmed cell death or apoptosis.
Then the dead cells' remains are ingested by
haemocytes, the fly equivalent of our macrophages.

"The paper's main contribution is that we provide first-time evidence of the role of the haemocytes, cells circulating in the fly haemolymph, in eliminating cell residues during competition," explains first author Fidel Lolo.

Co-author Sergio Casas-Tintó adds that the study's results indicate that the genes necessary for the haemocytes to eliminate these residues – in a process known as phagocytosis – are not required for the apoptosis of loser cells.

"We suggest that phagocytosis is not a cause
but a consequence of cell death,
and more work will need to be done
to determine the forces governing the selection
and subsequent destruction of losers."

Eduardo Moreno, University of Bern in Switzerland

Impications For Cancer
Cell competition is closely linked to pathogenic processes such as cancer.

Lolo: "There is growing evidence for the importance of these processes at tumor borders, where biological markers target an accumulation of dead cells, as if they were contemplating a line of battle."

Understanding the mechanisms of cell competition may provide crucial insights into the earliest stages of a tumor formation, favoring early detection, even without macroscopic evidence, and the design of new drugs able to block tumour growth from the very first development stages.

Referente article:
Cell competition timeline: winners kill losers, which are extruded and engulfed by hemocytes. Fidel-Nicolás Lolo, Sergio Casas Tinto and Eduardo Moreno. Cell Reports(2012). doi: 10.1016/j.celrep.2012.08.012

Original article: http://www.eurekalert.org/pub_releases/2012-09/cndi-nio091412.php