fetal development…

Medical experts recommend this detailed explanation.

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fetus, 10 weeks old, fetus, 12 weeks old, 16-week fetus, 24-week fetus, 26 to 28-week fetus, 30 to 32 week fetus, 3.5 week fetus, fetus, 7.5 weeks old, 8.5 week fetus, zygote, blastocyst, embryo, fetus, sperm is deposited, in the vagina, travels, the cervix, fallopian tubes, conception, takes place, in the fallopian tube, a single sperm penetrates the mother's egg cell, resulting cell, a zygote, zygote contains, the genetic information, dna, necessary to, become a child, half, the genetic information comes, mother's egg, half, father's sperm, zygote spends the next few days traveling down the fallopian tube, divides to form a ball of cells, further cell division creates an inner group of cells, an outer shell, stage, a "blastocyst", inner group of cells, become the embryo, outer group of cells, become the membranes that nourish, protect it, blastocyst reaches the uterus at roughly the fifth day, implants, uterine wall on, day six, in the mother's menstrual cycle, endometrium, lining, the uterus, has grown, ready to support a fetus, blastocyst adheres tightly, endometrium, where it receives nourishment via the mother's bloodstream, cells, the embryo now multiply, to take on specific functions, process, differentiation, produces the varied cell types that make up a human, blood cells, kidney cells, nerve cells, rapid growth, baby's main external features begin to take form, critical period of differentiation, the first trimester, growing baby, susceptible to damage, alcohol, certain prescription, recreational drugs, substances that cause birth defects, infection, rubella, cytomegalovirus, radiation from x-rays, radiation therapy, nutritional deficiencies, following list describes specific changes by week, week 3, beginning development, the brain, spinal cord, heart, beginning development, the gastrointestinal tract, weeks 4 to 5, formation of tissue that develops, vertebra, other bones, further development, the heart which now beats at a regular rhythm, movement of rudimentary blood, the main vessels, beginning, the structures, the eye, ears, brain develops into five areas, cranial nerves, visible, arm, leg buds, visible, week 6, beginning of formation, the lungs, further development, the brain, arms, legs have lengthened, foot, hand areas distinguishable, hands, feet have digits, still be webbed, week 7, nipples, hair follicles form, elbows, toes visible, all essential organs have at least begun to form, week 8, rotation of intestines, facial features continue to develop, eyelids, more developed, external features, the ear begin to take final shape, end, the eighth week marks the end, the "embryonic period", beginning, the "fetal period", weeks 9 to 12, fetus reaches a length of 3.2 inches, head comprises nearly half, the fetus' size, face is well formed, eyelids close, not reopen, the 28th week, tooth buds appear, the baby teeth, limbs, thin, fetus, make a fist, its fingers, genitals appear well differentiated, red blood cells, produced, in the liver, weeks 13 to 16, fetus reaches a length of, 6 inches, a fine hair develops on the head, lanugo, fetal skin is transparent, muscle tissue, bones have developed, bones, become harder, fetus makes active movements, sucking motions, the mouth, meconium is made, in the intestinal tract, liver, pancreas produce appropriate fluid secretions, week 20, fetus reaches a length of 8 inches, lanugo hair covers entire body, eyebrows, lashes appear, nails appear on fingers, toes, fetus is more active, increased muscle development, "quickening", occurs, mother, feel the fetus moving, fetal heartbeat, heard, a stethoscope, week 24, fetus reaches a length of 11.2 inches, fetus weighs, 1 lb, 10 oz, eyebrows, eyelashes, well formed, all the eye components, developed, fetus has a hand, startle reflex, footprints, fingerprints forming, alveoli, air sacs, forming in lungs, weeks 25 to 28, fetus reaches a length of 15 inches, fetus weighs, 2 lbs, 11 oz, rapid brain development, nervous system developed enough to control some body functions, eyelids open, respiratory system, immature, has developed, point where gas exchange is possible, a baby born at this time, survive, the possibilities, complications, death remain high, weeks 29 to 32, fetus reaches a length of, 15-17 inches, fetus weighs, 4 lbs, 6 oz, rapid increase, in the amount, body fat, rhythmic breathing movements occur, lungs, not fully mature, bones, fully developed, still soft, pliable, fetus begins storing iron, calcium, phosphorus, week 36, fetus reaches a length of, 16-19 inches, fetus weighs, 5 lbs, 12 oz, to 6 lbs, 12 oz, lanugo begins to disappear, increase in body fat, fingernails reach the end, the fingertips, a baby born at 36 weeks has a high chance of survival, require some medical interventions, weeks 37 to 40, considered full-term at 37 weeks, 19 to 21 inches in length, lanugo is gone except, on the upper arms, shoulders, fingernails extend beyond fingertips, small breast buds, present on both sexes, head hair is now coarse, thicker.