Reraed :how embryo becomes a fetus" medical 'lesson

From Embryo to Fetus in the womb : medical facts

by Gloria Poole,R.N.



There are several distinguishing features of the



transistion of an embryo to a fetus. Both of these words



are medical terms for a certain stage of development in



the womb. There is no abrupt change from the embryo to



the fetus. Instead there are cumulative changes that are



evolving day to day. The embryo changes from an



amorphous shape to more of a tiny human with all parts.



Also all of the major body organs have either appeared



or the precursor of them has developed. As the embryo



survives the second month in the womb, and is alive at



the beginning of the third month, the tiny human is less



vulnerable to the effects of disease in the mother, or



radiation of the mother, or medicines the mother may



have taken. Of course women who are pregnant should



never drink alcohol or use drugs! At any stage of the



pregnancy the baby in the womb is harmed by alcohol, and



many drugs have teratogenic effects. The term fetus is



appropriate after the major organs are either formed



entirely or the precursor of them is present e.g. for



the kidney. The fetus is still vulnerable but not as



much so, since the tiny human has a larger body and



therefore it would take larger doses of medicines



through the placenta to harm the tiny being, and the



tiny baby also has more developed organs to filter the



medicines that might pass to the baby through the



placenta. At the end of the first month after



fertilization the human embryo is about a quarter of an



inch in length from the top of the flat bulbous like



head to the end of the emerging legs that look at first



like a tail. Most of the organs are beginning to take



shape as the cells continuously divide and



differentiate. The tiny human develops by a 'blue print'



that is built into the chromosones and genes that the



tiny human received from the mother and from the father.



Twenty-three chromosones come from each parent in most



instances. In Down's syndrome the chromosones are



different. The baby's brain develops first since it is



needed first. The wisdom of GOD in creating humans is



obvious if you really study human anatomy and physiology



much. The outlines of eyes appear and a primitive mouth



and by 30 days after fertilization the three primary



parts of the brain are present , and the eyes, ears, and



nasal passages have begun to develop. The beginnings of



the backbone is present but that first month the tiny



embryo is sort of hunched together in a C shape. There



is no discernible arms or legs yet but the "tail" will



become legs. The heart will have started beating even



though it is not completely formed. The tiny human has



a closed circulatory system that includes the baby's own



blood vessels and also the umbilical cord and placenta



to the mother. The digestive tract opens from the mouth



downward for the first time on about the 28 th day



after fertilization by the male sperm. The liver appears



by about the 21 st day after fertilization. The thyroid



gland begins to form. The stomach, intestines,liver and



pancreas are there but there is no anus yet. The lungs



are not developed yet. Lung buds begin about day 27 and



the trachea [windpipe ] appears a few days after that.



By the time the tiny being would be called a fetus he or



she would have gained weight to one gram or about one-



thirtieth of an ounce, which is not as much as an



aspirin tablet but for the tiny human it is significant



progress since it means a 50-fold gain in body mass



gained during the second month over again what the tiny



human weighed at the end of four weeks after



fertilization. By day 31 muscles appear in the pelvis



and arms and legs begin to form and look sort of like a



bud on a tree in bloom.The valve separating the chambers



of the heart appear on day 31 or soon after. The germ



cells [sex determining] move along the mesoderm toward



the genital ridges and will form either ovaries or



testicles. By day 32 the caudal muscles appear [in what



becomes the baby's behind] and the last pair of gill-



like arches that will develop into lungs appears. By day



33 the cerebral cortex in the brain develops. By day 34



more of the muscles that will become the thighs and legs



develop and the stalk that separates the baby from the



yolk sac lengthens. By day 35 the primitive germ cells



have arrived in large numbers near the ridge that



develops into the kidney. And the olfactory part of the



brain that regulates small is present in the brain. By



the fifth week the tiny human is 8 millimeters or one-



third of an inch long from crown to rump and weighs



about 1/1000 of an ounce. The jaws are forming and the



face is beginning to look like a human face. The



umbilical cord is present and is the only part connected



to the placenta. The pituitary gland is forming in the



middle of the brain. The pharynx branches into the two



parts that will go to each lung. The membranes



[peritoneum] that separate the intestines form the chest



have formed and separate the lungs,heart and trachea



from the stomach and intestine. By day 36 the arm and



legs buds appear, and the 'tail' starts to shrink and



the baby may start moving about.

By day 37 the intestines have grown enough that they are



beginning to curve into their adult shape. The brain



stem that controls respiration is recognizable. By day



38 the jaws of upper and lower begin to look symmetrical



and with an mouth between them and the eye muscles have



begun to form in the orbits. Hands that look more like



paddles form and then when the fingers elongate they



look more like hands. The insides of the baby have grown



so fast that they sort of bulge and could be seen easily



through the almost transparent skin of the baby. By day



39 the nerve fibers are present to connect the sense of



smell of the olfactory nerves. By day 40 the pigment



[color] of the eyes could be seen through the



transparent skin also. The jaws are well formed and the



teeth, and facial muscles are forming also. The gill



arches disappear and the diaphragm appears that moves up



and down in respirations though the baby does not



breathe in the womb but later sort of practices that



effort. The liver starts producing red blood cells and



takes over from the yolk sac. By day 42 the reflexes



being and fingers and toes are more visible and the



beginnings of gonads are visible. By the sixth week the



fetus is 13 millimeters or half an inch long from crown



to rump. Cartilage that will become bone appears. The



head seems huge in relation to the rest of the body and



bends forward onto the chest since baby is still sort of



a C shape. Fingers appear. And the mammary glands begin.



The stomach and intestines rotate into position, muscles



lengthen and both cartilage and bone are visible in the



forming skeleton. The kidney has begun with the



pronephros the first but non-functioning kidneys. By day



44 the retinas of the eyes form, and also the palate of



the mouth and and the canals of the ear. By day 46 the



gonads are formed either ovaries or testicles so the sex



of the baby. Viola by day 48 after fertilization the



tiny human looks like a human! And is definitely a



fetus.

/s/ Gloria Poole, R.N. with reference from medical



textbook "From Conception to Birth' by Roberts Rugh and



Landrum B Shettles MDs.

The medical facts of how humans develop is written by me on another website of mine at:

http://onlineeducator.bravehost.com .

And the sketches I drew of some of the stages of human development and wanted to add to this website but they vanished from uploader AGAIN; so I added them to this website of mine:

http://onlineeducator.biz/

and look at the entry of yesterday 6-June-2009. They are a series of about 7 or 8 sketches in pencil and watercolor showing stages of development of human beings in the womb.

This document is owned by, and written by Gloria Poole,RN .@home in Missouri; 9:39am;9/Jan/2011