Pregnancy - 1st TrimesterPregnancy - 1st TrimesterWeeks 30 to 31 - Rapid brain growth; head size increasesWeeks 31 to 32 - Fetus begins to develop immune systemWeeks 33 to 34 - Gastrointestinal system still very immatureWeeks 35 to 36 - Body is round and plump with new fatWeeks 37 to 38 - Fetal liver is producing blood cellsWeeks 39 to 40 - Baby full termWeeks 39 to 40 - Baby full termWeeks 28 to 29 - Brain Surface Convolutions BeginWeeks 26 to 27 - Lungs begin to produce sufacantWeeks 24 to 25 - Sensory brain waves begin to activateWeeks 22 to 23 - Inner ear bones harden, hearing possibleWeeks 20 to 21 - Bone marrow starts making blood cellsWeeks 18 to 19 - Sexual organs now clearly visibleWeeks 16 to 17 - Fingerprints and toe prints beginWeeks 14 to 15 - Sexual organs now clearly visibleWeeks 12 to 13 - Fetus begins to move aroundWeeks 10 to 11 - Basic Brain Structure CompleteCarnegie Stage 23 - End of embryonic developmentCarnegie Stage 22 - Brain can move musclesCarnegie Stage 21 - Intestines MigrateCarnegie Stage 20 - Spontaneous MovementCarnegie Stage 19 - Semicircular Canals Forming in Inner EarCarnegie Stage 17 - Primitive germ cellsCarnegie Stage 16 - Hindbrain DevelopingCarnegie Stage 15 - Cerebral Hemispheres FormingCarnegie Stage 14 - Esophagus FormingCarnegie Stage 13 - First Layer Skin Carnegie Stage 12 - Upper Limb BudsCarnegie Stage 11 - Optic VesicleCarnegie Stage 10 - Neural Folds, Heart TubeCarnegie Stage 9 - First SomitesCarnegie Stage 8 - Primitive PitCarnegie Stage 7 - NeurulationCarnegie Stage 6 - GastrulationCarnegie Stage 5 - Implantation CompletedCarnegie Stage 4 - ImplantationCarnegie Stage 3 - Early Blastocyst Carnegie Stage 2 - CleavageCarnegie Stage 1 - Fertilization3rd Trimester Pregnancy2nd Trimester PregnancyCarnegie Stages - 1st Trimester Pregnancy

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What is The Visible Embryo?What Are The Carnegie Stages?Who Are The Content Experts?What is The Visible Embryo?Who Are The Content Experts?
Scientists measure. They measure circumference, length, weight, and anything else to do with the subject being studied. This is the only way to "see" what is not first seen by the naked eye. This is how to capture information that might be missed by simply looking or, possibly, by having a pre-existing idea of what that thing should look like or how it should work. Writing down every descriptive detail imaginable helps avoid the pitfall of pre-existing ideas determining how the subject being observed exactly looks and acts in a given moment.

The Carnegie Institutions' Department of Embryology reflects the search for such facts in human embryology.

Over the decades leading up to the foundation of Andrew Carnegie's Institution for scientific discovery in 1902, hundreds of embryologic specimens had been collected by doctors and sent to the Johns Hopkins Medical Institute in Baltimore, Maryland. By 1913, the Carnegie Institutes affiliated with the Johns Hopkins University and began a long process of classifying these specimens into a picture of embryonic development in very early pregnancy. The Carnegie Stages system of classifying embros began.

It is used by embryologists to describe approximately the first nine weeks of pregnancy. Carnegie Stages are numbered from 1 to 23 based on internal and external physical characteristics of the embryo. By stage 23, all essential internal organ systems are present but are incapable of sustaining independent life. The hallmarks of change described in each Carnegie Stage give molecular biologists aid in their search for patterns of chromosomal differentiation.
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.
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