Show Script Cover & Table of Contents
The dynamic process by which the single-cell human zygote(zī΄gōt)[1] becomes a 100 trillion (1014) cell adult[2] is perhaps the most remarkable phenomenon in all of nature.
Researchers now know that many of the routine functions performed by the adult body become established during pregnancy – often long before birth.[3]
The developmental period before birth is increasingly understood as a time of preparation during which the developing human acquires the many structures, and practices the many skills, needed for survival after birth.
Eno yengeli bu 'cell' bwo musaaja bwe gaata ne'ggi lwao mukaazi okufuka 'zygote' mukisera kino butuka amaagi amakulu obusilivo kikumi kino kyekimu kubyafayo mubyo butonde kunsi.
Bakakensa abononyereza ku misomo gino kakati batege ne'ngeri omubori gwomuntu bwe kolamu nga omukazi ali lubuuto mu myezi omwenda - nga omwana tanazali-bwa.
Okukula kwo mwana nga tanazalibwa kimanyidwa nga kisera kyo kutekateka umunto akula mulubuto afuna oba ebutindo byo mubiri, era omwana atandikiza okwegeza mubukodyo byana kuzesa ukobera wo kunsi nga'maze okuzalibwa.
Pregnancy in humans normally lasts approximately 38 weeks[4] as measured from the time of fertilization,[5] or conception,[6] until birth.
During the first 8 weeks following fertilization, the developing human is called an embryo,[7] which means "growing within."[8] This time, called the embryonic period,[9] is characterized by the formation of most major body systems.[10]
From the completion of 8 weeks until the end of pregnancy, "the developing human is called a fetus," which means "unborn offspring." During this time, called the fetal period, the body grows larger and its systems begin to function.[11]
All embryonic and fetal ages in this program refer to the time since fertilization.[12]
Mubantu olubuuto lutwa nga wiiki asaatu mumukaga okuva nga okuwa kubadewo, paka nga omwana azalidwa.
Wiiki ezisoka omunana nga owaku kumaze okubawo, omuntu akula mulubuuto ayijibwa bwa 'embryo,' amakalu gakyo nti ekikulila munda. Era ekisera kino kiwiti bwa 'embryonic period', kyekibamu okukula okwebitundi byomubiri ne nzirukanya yo'mubiri.
Okuva ku wiki omunana okutukira dala omwana bwazalibwa, omwana akuwa mumubiri ayitibwa 'fetus' mululimi ohwa kina sayinsi, amakulu nti owenda atabakuzalibwa. Mukisera kino ekiwitibwa 'fetal period', omubiri gwo ngera okugaja ne nzirukanya yo'mubiri edamunkola.
Ebisera ebya 'embryonic' ne 'fetal' mumitendera gino babayo okuva omukazi bwa waka.
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[1]
Gasser, 1975, 1.
[2]
Guyton and Hall, 2000, 2;
Lodish et al., 2000, 12.
[3]
Vindla and James, 1995, 598.
[4]
Cunningham et al., 2001, 226;
O’Rahilly and Müller, 2001, 92.
[5]
O’Rahilly and Müller, 1987, 9.
[6]
Spraycar, 1995, 377 & 637.
[7]
O’Rahilly and Müller, 2001, 87.
[8]
Quote from Ayto, 1990, 199.
[9]
Human development during the 8-week embryonic period has been divided into a series of 23 stages called Carnegie Stages. These stages are well described in O’Rahilly and Müller, 1987. Because human growth is unique and dependent on multiple factors, different embryos may reach a certain developmental milestone or a certain size at slightly different ages. This internationally-accepted staging system provides a way to describe development independent of age and size. Each of the 23 Carnegie Stages has specific structural features. As we describe various milestones of development, the Carnegie Stage at which they occur will be noted by a designation such as: [Carnegie Stage 2]. See Appendix B for additional information relating embryonic staging and age assignments.
[10]
Moore and Persaud, 2003, 3.
[11]
Quotes from Moore and Persaud, 2003, 3: “After the embryonic period (eight weeks), the developing human is called a fetus.“ Also see O’Rahilly and Müller, 2001, 87.
[12]
This convention, termed “postfertilization age“ by O’Rahilly, has been long preferred by embryologists. [see Mall, 1918, 400;
O’Rahilly and Müller, 1999b, 39;
O’Rahilly and Müller, 2001, 88 & 91.] Obstetricians and radiologists typically assign age based on the time elapsed since the first day of the last menstrual period prior to fertilization. This is correctly termed “postmenstrual age“ and begins 2 weeks before fertilization occurs. To summarize: postmenstrual age = postfertilization age + 2 weeks. Therefore, postmenstrual age equals approximately 2 weeks at the time of fertilization. The commonly used term “gestational age“ has been used with both age conventions and is best either avoided or carefully defined with each use.
Page 3
Biologically speaking, "human development begins at fertilization,"[13] when a woman and a man each combine 23 of their own chromosomes through the union of their reproductive cells.
A woman's reproductive cell is commonly called an "egg" but the correct term is oocyte (ō´ō-sīt).[14]
Likewise, a man's reproductive cell is widely known as a "sperm," but the preferred term is spermatozoon (sper´mă-tō-zō´on).[15]
Following the release of an oocyte from a woman's ovary in a process called ovulation (ov´yū-lā´shŭn),[16] the oocyte and spermatozoon join within one of the uterine tubes,[17] which are often referred to as Fallopian tubes.
The uterine tubes link a woman's ovaries to her uterus or womb.
The resulting single-celled embryo is called a zygote,[18] meaning "yoked or joined together."[19]
Mululimi lwa biologia "omuntu atandika okukula mukuwaka, omukaazi no'musaaja buli omu aleta abimusatu ku 'chromosomes'zabwe nga bu 'cell' bwabwe obuzala.
Ka 'cell' ko'mukaazi kagitibwa eggi oba 'egg' era neb u elinnya etifu lili 'oocyte'.
Era neb u 'cell' bwomusaaja bu manyidwa nga 'sperm' naye mululimi olufutifuti buyibwa 'spermatozoon'.
Eggi lwo'mukaazi bwe litebwa okuva mu 'ovary' mumitenda egiyitibwa 'ovulation', eggi oba 'oocyte' ne 'spermatozoon' bwegata kino kibawo mukamu kubu seke bwa mukaazi obuyitibwa 'fallopian tubes'.
Obuseke oba 'uterine tubes' bugata 'ovary' zo'mukaazi ku lubbuto oba nabana wo'mukaazi.
Ekivamwekyo nga bu 'cell' bwegase kiwitibwa 'zygote,' makulu nti waliwo okwegata.
DNA
The zygote's 46 chromosomes[20] represent the unique first edition of a new individual's complete genetic blueprint. This master plan resides in tightly coiled molecules called DNA. They contain the instructions for the development of the entire body.
DNA molecules resemble a twisted ladder known as a double helix.[21] The rungs of the ladder are made up of paired molecules, or bases, called guanine, cytosine, adenine, and thymine.
Guanine pairs only with cytosine, and adenine with thymine.[22] Each human cell contains approximately 3 billion (3×109) base pairs.[23]
The DNA of a single cell contains so much information that if it were represented in printed words, simply listing the first letter of each base would require over 1.5 million (1.5×106) pages of text![24]
If laid end-to-end, the DNA in a single human cell measures 3⅓ feet or 1 meter.[25]
If we could uncoil all of the DNA within an adult's 100 trillion (1014) cells, it would extend over 63 billion (6.3×1010) miles. This distance reaches from the earth to the sun and back 340 times.[26]
Cell Division
Approximately 24 to 30 hours after fertilization, the zygote completes its first cell division.[27] Through the process of mitosis, one cell splits into two, two into four, and so on.[28]
Early Pregnancy Factor (EPF)
As early as 24 to 48 hours after fertilization begins, pregnancy can be confirmed by detecting a hormone called "early pregnancy factor" in the mother's blood.[29]
DNA
'Zygote' oba neb u 'chrososomes' ana mumukaaga duno bwebu kikilila obulamu obusoka obwejawulo era eno eringa nlani yo'muntu mubutondebwe. Eno pulani sinziggu mu bu 'molucules' obwekute ate nga bunyole owitibwa 'DNA'. Muno mwemuli amateka gwo'kula Kwo mubiri gwona'ogwo muntu.
Bu 'DNA' 'molecules' bufanana nga edaala elinyoledwa liwitibwa 'double helix' omululimi oluna sayansi. Olwandi bade nga ozuda lwe daala olimu bu 'molecules' bubiri nga bwe kute, oba 'bases' owitibya 'guanine', Cytosine(syitsini), adanenine (adenayini), ne themine(tayanmani).
'Guanine' yegata na 'cytosine' yoka, ate 'adenine' neyegata ne 'thymine'. Bu ka 'cell' ko'muntu kabamu obuwubi basaatu obwa bu 'base pairs'.
'DNA'wa ka 'cell' akamu mulimu amakulu maagi akwata kumunto era singa yolekebwa mubiga mbo, nga enyukuta yoka esoka eya bu 'base' ye wandiki dwa kiba kitwetagisa akakade kamu nekitundu akempadila!
Era singa bu 'base' bugalimizibwa wansi kamu kukamu, 'DNA' owa ka 'cell'akamu alina obuwanvu bwa futi satu ne kitundu kimu kyakusatu oba mita emu.
Singa tusobola okuzi ngulula 'DNA' yena mumubiri gwo'muntu omukululu obusirivu ekikumi, oluzingululo luvamu obuwumbi nkaaga mubusatu obwa mayiro. Kino kilinga okuva wano no kutuka ku mjuba ate nokuda emirundi bisatu muana.
Cell Division
Oluvanyuma lwa sawa abiri munya no kutuka kusawa asatu nga okuwaka kuwede ka 'zygote' kamaliliza omulimu gwo'kwegabizamu ekiyitibwa. Kino kibayo kiyibya emitenderu ja 'mitosis', okusoka ka'cell'akamu kega'zamu bibiri ebiri nebyegbizamu bina ne kyeyo ngera mumaso byekityo.
Early Pregnancy Factor (EPF)
Oluvanyuma lwe sawa 24 paka ku sawa 48 nga okuwaka kutandi se, olubuuto luyinza okukukaka sibwa nga 'hormone' esangi dwa mumusaayi gwo mukaazi kiyitibwa 'early pregnancy factor'.
[13]
Quote from Moore and Persaud, 2003, 16;
From O’Rahilly and Müller, 1987, 9: “Fertilization is the procession of events that begins when a spermatozoon makes contact with an oocyte or its investments and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote.“ See Carlson, 2004, 3;
O’Rahilly and Müller, 2001, 8. [Carnegie Stage 1]
[14]
O’Rahilly and Müller, 2001, 25: “The term ‘egg’ should be discarded from human embryology.“ From O’Rahilly and Müller, 1987, 9: “The term ‘egg’ is best reserved for a nutritive object frequently seen on the breakfast table.“
[15]
O’Rahilly and Müller, 2001, 23-24.
[16]
O’Rahilly and Müller, 2001, 30.
[17]
Dorland and Bartelmez, 1922, 372;
Gasser, 1975, 1;
Mall, 1918, 421;
O’Rahilly and Müller, 2001, 31.
[18]
Gasser, 1975, 1;
O’Rahilly and Müller, 2001, 33.
[19]
Quote from Saunders, 1970, 1;
Spraycar, 1995, 1976.
[20]
Guyton and Hall, 2000, 34.
[21]
Guyton and Hall, 2000, 24;
Watson and Crick, 1953, 737.
[22]
Guyton and Hall, 2000, 24;
Lodish et al., 2000, 103;
Watson and Crick, 1953, 737.
[23]
Lodish et al., 2000, 456.
[24]
See Appendix A.
[25]
See Appendix A;
Alberts et al., 1998, 189.
[26]
See Appendix A.
[27]
Hertig, 1968, 26;
Hertig and Rock, 1973, 130;
(cited by O’Rahilly and Müller, 1987, 12);
Shettles, 1958, 400.
[28]
Guyton and Hall, 2000, 34.
[29]
Moore and Persaud, 2003, 33 & 60;
Morton et al., 1992, 72;
Nahhas and Barnea, 1990, 105.
Page 4
By 3 to 4 days after fertilization, the dividing cells of the embryo assume a spherical shape and the embryo is called a morula (mōr´ū-lă).[30]
By 4 to 5 days, a cavity forms within this ball of cells and the embryo is then called a blastocyst.[31]
The cells inside the blastocyst are called the inner cell mass and give rise to the head, body, and other structures vital to the developing human.[32]
Cells within the inner cell mass are called embryonic stem cells because they have the ability to form each of the more than 200 cell types contained in the human body.[33]
Oluvanyu lwe naku satu okutuka kunaku nya nga okuwaka kuwede, bu 'cell' bwa 'embryo'obuba bwegabizamu bufuka bwetolovu era 'embryo' kakno eyitibya 'morula'.
Oluvanyuma lwenaku 4 okutuka kunaku 5 egeri yakasawo kuwambako bu 'cell' buno kakano 'embryo' eyitibya 'blastocyst'.
Bu 'cells' munda wako ka 'blastocyst' buyitibwa 'inner cell mass' era mwemuua ebitundu nga omutwe omubiri nebitundu ebira ebyo mubiri ebyo mugaso eli okukula kwomuntu.
Bu 'cell' obubamu 'inner cell mass' buyitibwa 'embryonic stem cell' kubanga bulina obusobozi obwo kufuka mu buli emu kwa bu 'cells' obwebika ebibiri obubera mumubiri gwo muntu.
After traveling down the uterine tube, the early embryo embeds itself into the inner wall of the mother's uterus. This process, called implantation, begins 6 days and ends 10 to 12 days after fertilization.[34]
Cells from the growing embryo begin to produce a hormone called human chorionic gonadotropin (human kō-rē-on'ik gō'nad-ō-trō'pin), or hCG, the substance detected by most pregnancy tests.[35]
HCG directs maternal hormones to interrupt the normal menstrual cycle, allowing pregnancy to continue.[36]
Bwebumala okuyita mu kaseke akiyitibwa akanaba na oba 'uterine tube', munaku ezisoka 'embryo' eyigira mukasenge kasuka 'inner wall' akanabana. Emitendera gino egiyitibwa okwesiba (implatantion) kutandika munuka mukaaga era nekugwa wakati wenaku kumi ne kumimanya nga okuwaka kuwede.
Bu 'cell' bwo mu 'embryo' butamdika okukula busubole okuleta 'hormone' eyuitibwa 'human chorionic gonadotropin'/ hcg, eno elabibwa nga omukaazi akebelwa oba'li lubuuto.
Eno 'HCG' yelagila 'maternal hormone' okuziwiza ogenda mumwezi okwabakaazi(menstrual cycle), kino ne kiyamba egwako oba olubuuto okugenda mumaso.
Following implantation, cells on the periphery of the blastocyst give rise to part of a structure called the placenta (plă-sen'tă), which serves as an interface between the maternal and embryonic circulatory systems.
The placenta delivers maternal oxygen, nutrients, hormones, and medications to the developing human; removes all waste products; and prevents maternal blood from mixing with the blood of the embryo and fetus.[37]
The placenta also produces hormones and maintains embryonic and fetal body temperature slightly above that of the mother's.[38]
The placenta communicates with the developing human through the vessels of the umbilical (ŭm-bil'i-kăl) cord.[39]
The life support capabilities of the placenta rival those of intensive care units found in modern hospitals.
Nga okwe-simba kuwede, bu 'cell' kukusakate kua-kasawo kano aka 'blastocyte' bufukamu ekitundu kua 'placenta', kino kibanga olutimbe olugata 'maternal' ne'ntabula yo musaayi mu 'emrbyo'.
Eno 'placenta' yeleta omuuka, ogwo kusa era ne'birisa neb u 'hormones' gatako ne'dagala omwana lweyetaga ebyo mugaso mukukula kwo'mwana era elongosa sako no twala kalonda yena atetagisa; era eziyiza no musaayi gwa maama okwegata no'gwo mwana.
Era ekola ne bu 'hormones' sako no kulaba nga ebu gume lwa 'embryo' ne lwa 'fetal' lyelyo elisade era okubuguma kwabyo kulina okusuka ko katuno okwa maama.
Omwana owo'kubiri oba(Placenta) ewuliziganya ne omwana mulubuuto nga eyifamu 'vessels' obwa kundi oba 'umblical cord'.
Obusobozi byo kuwagi omwana nga akula obwa omwana owo'kubiri bufanana ko no bwo obwa 'intensive care' oba okulabililwa enyo mu awauro elwo mulemmbe.
[30]
Gasser, 1975, 1;
O’Rahilly and Müller, 2001, 37;
Spraycar, 1995, 1130: “Morula“ is derived from the Latin word morus meaning “mulberry.“ [Carnegie Stage 2]
[31]
O’Rahilly and Müller, 2001, 39. [Carnegie Stage 3]
[32]
Gasser, 1975, 1;
O’Rahilly and Müller, 2001, 39;
Sadler, 2005, 6.
[33]
Alberts et al., 1998, 32. For a discussion and definition of embryonic stem cells see the website of the National Institutes of Health: http://stemcells.nih.gov/infoCenter/stemCellBasics.asp#3
[34]
O’Rahilly and Müller, 2001, 40;
Implantation begins with attachment of the blastocyst at about 6 days after fertilization. [Attachment of the blastocyst to the inner wall of the uterus is a transient event and is the hallmark of Carnegie Stage 4.] See also Adams, 1960, 13-14;
Cunningham et al., 2001, 20;
Hamilton, 1949, 285-286;
Hertig, 1968, 41;
Hertig and Rock, 1944, 182;
Hertig and Rock, 1945, 81 & 83;
Hertig and Rock, 1949, 183;
Hertig et al., 1956, 444. [Carnegie Stage 5]
[35]
Chartier et al., 1979, 134;
Cunningham et al., 2001, 27;
O’Rahilly and Müller, 2001, 43.
[36]
Cunningham et al., 2001, 20 & 26-27;
O’Rahilly and Müller, 2001, 31.
[37]
Hertig, 1968, 16;
Cunningham et al., 2001, 86 & 136;
For a detailed description of the placenta see Hamilton and Boyd, 1960. For a detailed description of the placenta vasculature see Harris and Ramsey, 1966. This separation of maternal and fetal blood is almost but not quite perfect as a
small number of fetal cells may be found in the maternal circulation and vice-versa. See Cunningham et al., 2001, 96 & 136.
[38]
Liley, 1972, 101;
O’Rahilly and Müller, 2001, 78-79.
[39]
For a detailed description of umbilical cord formation see Florian, 1930.
Page 5
By 1 week, cells of the inner cell mass form two layers called the hypoblast and epiblast.[40]
The hypoblast gives rise to the yolk sac,[41] which is one of the structures through which the mother supplies nutrients to the early embryo.[42]
Cells from the epiblast form a membrane called the amnion (am-nē-on),[43] within which the embryo and later the fetus develop until birth.
Oluvanyuma lwa wiiki bu 'cell' obwa 'inner cell mass' bwekolamu oba bufuka engeri yembudi birieyitibwa 'hypbolast' ne 'epiblast'.
'Hypoblast' yevamu oba yefuka mu akasawo kenjuba oba 'yolk sac', maama okuwa omwana ebirisa munaku ezi sokera dala eza 'embryo'.
Bu 'cell' okuva mu 'epiblast' bwebufukamu engeriya kabubi oba'kasawo akayiitibya 'amnion,' muno ka 'embryo' era ne dako ka 'fetus' mwebikulila paka okuzalibwa.
By approximately 2½ weeks, the epiblast has formed 3 specialized tissues, or germ layers, called ectoderm, endoderm, and mesoderm.[44]
Ectoderm gives rise to numerous structures including the brain, spinal cord, nerves, skin, nails, and hair.
Endoderm produces the lining of the respiratory system and digestive tract and generates portions of major organs such as the liver and pancreas.
Mesoderm forms the heart, kidneys, bones, cartilage, muscles, blood cells, and other structures.[45]
By 3 weeks the brain is dividing into 3 primary sections called the forebrain, midbrain, and hindbrain.[46]
Development of the respiratory and digestive systems is also underway.[47]
As the first blood cells appear in the yolk sac,[48] blood vessels form throughout the embryo, and the tubular heart emerges.[49]
Almost immediately, the rapidly growing heart folds in upon itself as separate chambers begin to develop.[50]
The heart begins beating 3 weeks and 1 day following fertilization.[51]
The circulatory system is the first body system, or group of related organs, to achieve a functional state.[52]
Mu wiiki biri ne kitundu ka 'epiblast' kabakakuze era obubiri obwo mugaso busatu, oba obubiri oyitabwa 'germ layers,' aka 'ectoderm,' 'endoderm,' naka 'mesoderm'.
'Ectoderm' evamu ebitundu bwomubiri bingi gamba nga obwongo, olugongogongo oba (spinal cord) obusimo bwo mubiri, olususu, enjala, ne'nuiri.
'Endoderm' yefuka mu akabili abika kumawugwe, era ne omubu ogutwa emere ne ne nebwenda, era evamu ne bitundu bwo'mubiri ebyomugaso gamba nga ekibumba ne kalululwe oba 'pancrease'.
'Mesoderm' yo evamu oba efukamu omutima, ensigo, amagumba, 'cartilage' oba magumba'magonuu, ebinywa, bu 'cells' byo musaayi, ne bitundu byo mubiri ebilala.
Oluvanyuma lwa wiiki satu obwongo bugabanyibwamu ebitundu bisatu ekiyitibwa obwo obusokelwa ko oba 'forebrain' obwongo'bwo mumakati oba 'midbrain,' era ne obwongo 'bwe mabega oba 'hindbrain.'
Okukula kwebi kwata kukusa ne bwokukozesa no'kumenya menya emere mumubiri kuba kugenda mumaso.
Nga bu 'cell' bwo musaayi bwebweyoleka mu kasawo kenjuba oba 'yolk sac,' ne obuseke bwo musaayi, nabwo bukula okubuna 'embryo' yona, era no'mutima omwagagauo nagwo guba gutuze.
Kumpi mukisera kyekimu, omutima ogubagukula amangu gwe yumba-ko era ebisenge ebyawufu bitandi okweyoleka oba okwe zimba.
Omutima gutandi okukuba mu wiiki satu no'lunaki nga okuwaka 'fertilization' kuwede.
Otambula kwo musayi kwekusooka okutandiika okukola, oba ebitundu byo mubiri ebi kwata gaa no'musaayi, kino eberewo'kudukana kwomubiri kusobole kuberawo.
Between 3 and 4 weeks, the body plan emerges as the brain, spinal cord, and heart of the embryo are easily identified alongside the yolk sac.
Rapid growth causes folding of the relatively flat embryo.[53] This process incorporates part of the yolk sac into the lining of the digestive system and forms the chest and abdominal cavities of the developing human.[54]
Mubanga nga ya wiiki saatu oba nnya, kakano 'plani' yomubiri etandikwa wo gwi obwongo, olugongogongo oba'spinal cord' ne omutima gwa 'embryo' byangu byakwawula era no'kulaba Mu kasawo kenjuba 'yolk sac.'
Okukula kwo mutiima amangu enyo kuleta okwewumba okwa 'embryo.' Omitendera gino gigata ebitundu bya 'yolk sac' mu 'lining' oba akakuta emitendera joku menya menya emere mumubiri muno mwemuva ekifuba kyo munju ne bitundu ebyawansi oba 'abdominal cavities' ebya munju akula.
[40]
O’Rahilly and Müller, 2001, 39.
[41]
Moore and Persaud, 2003, 50;
O’Rahilly and Müller, 2001, 82. [Carnegie Stages 5 & 6];
In humans, the term “yolk sac“ has fallen out of favor among some embryologists (including O’Rahilly and Müller) because it is not a nutrient reservoir and does not contain yolk. The technically preferred term is umbilical vesicle. This structure plays a vital role in the transfer of nutrients from mother to embryo before placental circulation becomes fully functional.
[42]
Campbell et al., 1993, 756;
Kurjak et al., 1994, 437;
O’Rahilly and Müller, 2001, 82.
[43]
O’Rahilly and Müller, 1987, 29;
O’Rahilly and Müller, 2001, 43. [Carnegie Stages 4-5]
[44]
O’Rahilly and Müller, 2001, 14 & 135. [Carnegie Stage 7];
It should be noted there are many examples of organs derived from multiple germ layers. For instance, the liver is largely derived from endoderm but contains blood vessels and blood cells derived from mesoderm and nerves of ectodermal origin.
[45] Moore
and Persaud, 2003, 80 & 83; Sadler, 2005, 9.
[46]
Bartelmez, 1923, 236;
Müller and O’Rahilly, 1983, 419-420 & 429;
O’Rahilly and Gardner, 1979, 123 & 129;
O’Rahilly and Müller, 1984, 422;
O’Rahilly and Müller, 1987, 90;
O’Rahilly and Müller, 1999a, 47 & 52. [Carnegie Stage 9]
[47]
DiFiore and Wilson, 1994, 221;
Fowler et al., 1988, 793;
Grand et al., 1976, 793-794 & 796 & 798;
O’Rahilly, 1978, 125;
O’Rahilly and Boyden, 1973, 238-239;
O’Rahilly and Müller, 1984, 421;
O’Rahilly and Tucker, 1973, 6 & 8 & 23;
Streeter, 1942, 232 & 235.
[48]
Carlson, 2004, 117.
[49]
Gilmour, 1941, 28;
O’Rahilly and Müller, 1987, 86. [Carnegie Stage 9]
[50]
Campbell, 2004, 14;
Carlson, 2004, 116 & 446;
Navaratnam, 1991, 147-148;
O’Rahilly and Müller, 1987, 99. [Carnegie Stage 10]
[51]
Campbell, 2004, 14;
Carlson, 2004, 430;
De Vries and Saunders, 1962, 96;
Gardner and O’Rahilly, 1976, 583;
Gilbert-Barness and Debich-Spicer, 1997, 650;
Gittenger-de Groot et al., 2000, 17;
van Heeswijk et al., 1990, 151;
Kurjak and Chervenak, 1994, 439;
Navaratnam, 1991, 147-148;
O’Rahilly and Müller, 1987, 99;
Wisser and Dirschedl, 1994, 108. [Carnegie Stage 10, possibly late Stage 9]
[52]
Moore and Persaud, 2003, 70: “The cardiovascular system is the first organ system to reach a functional state.“
[53]
Moore and Persaud, 2003, 78.
[54]
Gasser, 1975, 26;
Moore and Persaud, 2003, 78.
Page 6
By 4 weeks the clear amnion surrounds the embryo in a fluid-filled sac.[55] This sterile liquid, called amniotic (am-nē-ot'ik) fluid, provides the embryo with protection from injury.[56]
Mu wiiki nya 'embryo' yetololwa amari amatangauu agayitibwa 'aminion' mu kasaswo ka'maazi. Amaazi gano agaba mukasawo omwana mwakulira, gayitibwa 'aminiotic fluid' geega yamba 'embryo'okukuma no'kuyiiza ebisago omwana bye yandi tuseko mulubuuto.
The heart typically beats about 113 times per minute.[57]
Note how the heart changes color as blood enters and leaves its chambers with each beat.
The heart will beat approximately 54 million (5.4×107) times before birth and over 3.2 billion (3.2×109) times over the course of an 80-year lifespan.[58]
Omutima kakano gukuba emirundi kikumi mukumi nesatu buli dakika.
Laba mti'omutima gukyusa langi nga omusayi bweguyingira ne bwegufuluma 'chambers' nga omutima gukuba.
Omutima gukuba nga emirundi obukadde atano mu ena omwana nga tanazalibwa emirundi obuwumbi busatu mu okadde bibiri omuntu nga'wangadde emyaka kinaana.
Upper and lower limb development begins with the appearance of the limb buds by 4 weeks.[59]
The skin is transparent at this point because it is only one cell thick.
As the skin thickens, it will lose this transparency, which means that we will only be able to watch internal organs develop for about another month.[60]
Emiko na'magulu bitandiika okukula mu wiiki nya egeliyo bugulo no'bukono butandikiriza okulabi.
Omubiri mutangavu kukisera kino kubanga akabiri ka 'cell' kamu koka kekagubika.
Olususu bwelutandikiza oku okukula, olulekerawo okuba olutangavu, ekitegeza nti tuja kulaba ebye yomubiri nga bikula okula okumala omwezi gumu omulala.
Between 4 and 5 weeks, the brain continues its rapid growth and divides into five distinct sections.[61]
The head comprises about one-third of the embryo's total size.[62]
The cerebral (ser'ĕ-brăl) hemispheres appear,[63] gradually becoming the largest parts of the brain.[64]
Functions eventually controlled by the cerebral hemispheres include thought, learning, memory, speech, vision, hearing, voluntary movement, and problem-solving.[65]
Mubanga lya wiiki nya oba tano, obwongo bweyongera okukula amangu'dala era bwegabanyamu ebitundu bitano ebyeyawufu.
Omutwe gubamu ebitundu kimu kyaku satu ekyo byagagauu bwa 'embryo'.
Ekitundu kiyitibwa 'celebral hemisphere' kitandiika okweyo leka era mpola mpolia ne'bitundu byo'bwongo.
Emigaso gitambulizibwa oba egifugibwa 'celebral hemispheres' biri nga okuyiga ,okulowoza, okujikira' okwogera'okulaba' okuwulira' okutambula kwomubiri otariko kulowoza, no'kutereza ensobi.
[55]
Gasser, 1975, 30;
O’Rahilly and Müller, 2001, 80.
[56]
O’Rahilly and Müller, 2001, 81.
[57]
van Heeswijk et al., 1990, 153.
[58]
See Appendix A.
[59]
Gasser, 1975, 49 & 59;
O’Rahilly and Gardner, 1975, 11;
O’Rahilly and Müller, 1985, 148 & 151;
O’Rahilly and Müller, 1987, 143;
Streeter, 1945, 30;
Uhthoff, 1990, 7 & 141. [upper and lower limb buds: Carnegie Stages 12 & 13]
[60]
Moore and Persaud, 2003, 486;
O’Rahilly, 1957, 459;
O’Rahilly and Müller, 2001, 165. For information about the first-trimester, direct-imaging technique used in this program (called embryoscopy), see Cullen et al., 1990.
[61]
O’Rahilly and Müller, 1999a, 134;
Sadler, 2005, 106. [Carnegie Stage 15]
[62]
Laffont, 1982, 5.
[63]
Bartelmez and Dekaban, 1962, 25;
Campbell, 2004, 17;
O’Rahilly and Gardner, 1979, 130;
O’Rahilly et al., 1984, 249;
O’Rahilly and Müller, 1999a, 115;
van Dongen and Goudie, 1980, 193. [Carnegie Stage 14]
[64]
Moore, 1980, 938.
[65]
Guyton and Hall, 2000, 663-677.
Page 7
In the respiratory system, the right and left main stem bronchi (brong'kī) are present[66] and will eventually connect the trachea (trā´kē-ă), or windpipe, with the lungs.
Note the massive liver filling the abdomen adjacent to the beating heart.
The permanent kidneys appear by 5 weeks.[67]
The yolk sac contains early reproductive cells called germ cells. By 5 weeks these germ cells migrate to the reproductive organs adjacent to the kidneys.[68]
[66]
Moore and Persaud, 2003, 245;
O’Rahilly and Boyden, 1973, 239;
O’Rahilly and Müller, 2001, 291;
Sparrow et al., 1999, 550.
[67]
Angtuaco et al., 1999, 13;
Lipschutz, 1998, 384; Moore and Persaud, 2003, 288;
O’Rahilly and Müller, 1987, 167 & 182;
O’Rahilly and Müller, 2001, 301;
Sadler, 2005, 72. [Carnegie Stage 14]
[68]
O’Rahilly and Müller, 2001, 23;
Waters and Trainer, 1996, 16;
Witschi, 1948, 70, 77 & 79.
[69]
O’Rahilly and Müller, 1987, 175;
Streeter, 1948, 139. [Carnegie Stage 15 ]
[70]
O’Rahilly and Gardner, 1975, 4. [Carnegie Stages 16 and 17 ]
Page 8
By 6 weeks the cerebral hemispheres are growing disproportionately faster than other sections of the brain.
The embryo begins to make spontaneous and reflexive movements.[71] Such movement is necessary to promote normal neuromuscular development.
A touch to the mouth area causes the embryo to reflexively withdraw its head.[72]
Mu wiiki mukaaga 'celebral hemisphere' zi tandi okukula mangu kko okusoka ebitundu byo'bwongo ebilala.
'Embryo' etandika okutambula empola no'kutambula mugere etetagisa kulowoza. Entambula ewo yetagisa Okugenda mumaso ne'okuwagila 'neuro-muscular development'.
Okukona oba okukwata ku mutwe gwa 'embryo' kuvamu okukweka kwomutwe gwawo.
The external ear is beginning to take shape.[73]
By 6 weeks, blood cell formation is underway in the liver where lymphocytes are now present.[74] This type of white blood cell is a key part of the developing immune system.
Ebitundu bya'matu ebyawabweru bitandika okufuna 'shape' oba okwe bumba.
Mu wiiki mukaaga, bu 'blood cells' butandika okweyo leka oba okukula mukibuba kakono bu 'lymphocytes'webuli. Ekika kya 'white blood cell' kya mugaso nyo mukuzimba 'systems'. ewokulwanyi endwade mumubiri
The diaphragm (dī'ă-fram), the primary muscle used in breathing, is largely formed by 6 weeks.[75]
A portion of the intestine now protrudes temporarily into the umbilical cord. This normal process, called physiologic herniation (fiz-ē-ō-loj'ik her-nē-ā'shŭn), makes room for other developing organs in the abdomen.[76]
Ekinywa kya akabengo oba'diaphragm', ebezewo okusa mubiri, eba ekuze muwiiki nga mukaaga.
Okitundu kye bwende kakano kivayo okumala esera munda ye kundi. Kino kiwitibwa 'physiologic herniation' kino kibowo ebitundu byomubiri bisobole okukula mubitundu ebya wansi.
[71]
Birnholz et al., 1978, 539;
de Vries et al., 1982, 301 & 304: “The first movements were observed at 7.5 weeks postmenstrual age.“ [or 5½ weeks postfertilization age];
Humphrey, 1964, 99: earliest reflex 5½ weeks;
Humphrey, 1970, 12;
Humphrey and Hooker, 1959, 76;
Humphrey and Hooker, 1961, 147;
Kurjak and Chervenak, 1994, 48;
Visser et al., 1992, 175-176: “Endogenously generated fetal movements can first be observed after 7 weeks postmenstrual age (i.e. 5 weeks after conception);“
Natsuyama, 1991, 13;
O’Rahilly and Müller, 1999a, 336: 5½ weeks postfertilization;
Sorokin and Dierker, 1982, 723 & 726;
Visser et al., 1992, 175-176;
Natsuyama, 1991, 13: Spontaneous movement observed by “Carnegie stage 15“ (about 33 days postfertilization);
Hogg, 1941, 373: Reflex activity begins at 6½ weeks [adjusted to postfertilization age].
[72]
Goodlin, 1979, D-128.
[73]
Karmody and Annino, 1995, 251;
O’Rahilly and Müller, 2001, 480;
Streeter, 1948, 190.
[74]
Kurjak and Chervenak, 1994, 19.
[75]
de Vries et al., 1982, 320.
[76]
Gilbert-Barness and Debich-Spicer, 1997, 774;
Grand et al., 1976, 798;
O’Rahilly and Müller, 1987, 213;
Sadler, 2005, 66;
Spencer, 1960, 9;
Timor-Tritsch et al., 1990, 287.
[77]
O’Rahilly and Müller, 1987, 202-203.
[78]
Borkowski and Bernstine, 1955, 363 (cited by Bernstine, 1961, 63 & 66;
O’Rahilly and Müller, 1999a, 195;
van Dongen and Goudie, 1980, 193.);
Hamlin, 1964, 113. For a summary of in utero fetal encephalography (measuring brainwaves) in the near- term fetus using abdominal and vaginal electrodes see Bernstine et al., 1955.
Page 9
Nipples appear along the sides of the trunk shortly before reaching their final location on the front of the chest.[79]
By 6½ weeks, the elbows are distinct, the fingers are beginning to separate,[80] and hand movement can be seen.
Bone formation, called ossification (os'i-fi-kā'shŭn), begins within the clavicle, or collar bone, and the bones of the upper and lower jaw.[81]
Mu wiiki nga mukaaga nekintundu obukokola bulabika, ne ngalo zitando okweyoyawula, era ne'mikono kitandi okutambula.
Okukukwa magumba kutandi, kino witibwa 'ossification' kino kitandika okuba mu 'clavicle' oba egumba lwe'kibegabega, Era na'magumba ge'mba olwa'wasi newagulu.
[79]
O’Rahilly and Müller, 1985, 155: “The nipple appears at stages 17 and 18.“ [41-44 days postfertilization];
Wells, 1954, 126.
[80]
O’Rahilly and Müller, 2001, 221;
Streeter, 1948, 187.
[81]
Carlson, 2004, 189;
O’Rahilly and Gardner, 1972, 293;
O’Rahilly and Gardner, 1975, 19;
O’Rahilly and Müller, 2001, 385;
Sperber, 1989, 122 & 147. [Carnegie Stage 19]
[82]
de Vries et al., 1982, 305 & 311;
Visser et al., 1992, 176.
[83]
de Vries et al., 1988, 96;
Visser et al., 1992, 176.
[84]
Cooper and O’Rahilly, 1971, 292;
James, 1970, 214; Jordaan, 1979, 214;
Streeter, 1948, 192;
Vernall, 1962, 23: “The four chambers of the heart and the associated major vessels are externally apparent in a close approximation to their adult positions.“ [Carnegie Stage 18]
[85]
van Heeswijk et al., 1990, 153.
[86]
Straus et al., 1961, 446 (cited by Gardner and O’Rahilly, 1976, 571.): “…an electrocardiogram with the classical P, QRS, and T configuration has been obtained from a 23mm human embryo (Straus, Walker, and Cohen, 1961).“
[87]
O’Rahilly and Müller, 2001, 320. [Carnegie Stage 20]
[88]
Andersen et al., 1965, 646;
O’Rahilly, 1966, 35;
O’Rahilly and Müller, 1987, 259;
Pearson, 1980, 39;
Streeter, 1951, 193. [Carnegie Stage 22] Pigment within the retina is present from about 37 days postfertilization per O’Rahilly, 1966, 25. [Carnegie Stage 16]
[89]
Streeter, 1951, 191;
reiterated by O’Rahilly and Müller, 1987, 257.
[90] O’Rahilly and Gardner, 1975, 11;
O’Rahilly and Müller, 1987, 262.
Page 10
By 8 weeks, 75 percent of embryos exhibit right-hand dominance. The remainder is equally divided between left-handed dominance and no preference. This is the earliest evidence of right- or left-handed behavior.[93]
Pediatric textbooks describe the ability to "roll over" as appearing 10 to 20 weeks after birth.[94] However, this impressive coordination is displayed much earlier in the low-gravity environment of the fluid-filled amniotic sac.[95] Only the lack of strength required to overcome the higher gravitational force outside the uterus prevents newborns from rolling over.[96]
The embryo is becoming more physically active during this time.
Motions may be slow or rapid, single or repetitive, spontaneous or reflexive.
Head rotation, neck extension, and hand-to-face contact occur more often.[97]
Touching the embryo elicits squinting, jaw movement, grasping motions, and toe pointing.[98]
Ebitabo byabasawo ba'baana abato biyogera ku busobozi bwo kwekyusa olvunya lwa wiiki kumi oba abiri lovavunyuma lwo kuzalibwa. Engeri, eno eyo'kufuga no kutabuliza omubiri eoja mangu mubitundi ebiri na 'gravity' omutono amaali agali mu 'amniotic sac'. Obutabera mamanyi getagisa okusinga 'gravity' wabweru 'uterus' eliyiza abana abato okwevunula.
Wanu 'embryo'eba efuuka eyomugaso mukisera kino.
Okutabulia kwebitundu byomubiri kuyiza okuba-wo amangu oba empola omulundu gumu oba emirundi egidiringana, etagisa okulowoza oba etitagisa.
Omutwe okwetolola, ensingo okuwanvuwa ne'mikono okutandi okukwata bibera emirundi mingi.
Okukwata ku 'embryo' kivamu okutoniya amaaso, okutambuza emba, okukwata mumiko, no bugere okusunga no kuwamvu virile.
Between 7 and 8 weeks, the upper and lower eyelids rapidly grow over the eyes and partially fuse together.[99]
Although there is no air in the uterus, the embryo displays intermittent breathing motions by 8 weeks.[100]
By this time, kidneys produce urine which is released into the amniotic fluid.[101]
In male embryos, the developing testes begin to produce and release testosterone (tes-tos´tĕ-rōn).[102]
Ne wankusubade tei mpewo mu 'uterus', 'embryo' eragaoba eba ne okutambula okulaga okusa.
Kukisera kino ensingo zivamu omusulo gugenda mu maazi aga 'amniotic fluid'.
Mubasaaja bu 'testes' oba mubasaaja obu sawo obuteleka amaggi butandika okufulumya 'testosterone'.
Eight weeks marks the end of the embryonic period.
During this time, the human embryo has grown from a single cell into the nearly 1 billion (109) cells[106] which form over 4,000 (4×103) distinct anatomic structures.
The embryo now possesses more than 90 percent of the structures found in adults.[107]
Kuwiiki munana okukula kwa 'embryonic period' kukoma.
Mukisega kino 'embryo' yo'mune eba ekuze okuva mu 'cell' emu okutukaranga akuwumbi kamu aka 'cell' evamu 'anatomic structures' enkumi nya,
'Embryo' kakano erina ebitundu kyenda kukikumi ebisangi bwa mumubiri gwo'muntu wakulu.
[91]
O’Rahilly and Müller, 1999a, 288: “The brain at [Carnegie] Stage 23 is far more advanced morphologically than is generally appreciated, to such an extent that functional considerations are imperative.“
[92]
Jordaan, 1979, 149.
[93]
Hepper et al., 1998, 531;
McCartney and Hepper, 1999, 86.
[94]
Bates, 1987, 534.
[95]
de Vries et al., 1982, 320;
Goodlin and Lowe, 1974, 348;
Humphrey, 1970, 8.
[96]
Liley, 1972, 101.
[97]
de Vries et al., 1982, 311.
[98]
Humphrey, 1964, 102;
Humphrey, 1970, 19.
[99]
Process described by Andersen et al., 1965, 648-649;
O’Rahilly, 1966, 36-37;
O’Rahilly and Müller, 1987, 261. [Carnegie Stage 23]
[100]
Connors et al., 1989, 932;
de Vries et al., 1982, 311;
McCray, 1993, 579;
Visser et al.,1992, 177.
[101]
O’Rahilly and Müller, 2001, 304;
Windle, 1940, 118; (Windle reports urine formation begins at nine weeks.)
[102]
Moore and Persaud, 2003, 307;
Waters and Trainer, 1996, 16-17.
[103]
O’Rahilly and Gardner, 1975, 15: ”By the end of the embryonic proper (Stage 23, 8 postovulatory weeks), all of the major skeletal, articular, muscular, neural, and vascular elements of the limbs are present in a form and arrangement closely resembling those of the adult.“ See O’Rahilly,
1957, for a summary of joint types and a description of limb joint development during the embryonic period. See Gray et al., 1957, for a detailed examination of the bones and joints of the hand throughout the embryonic and fetal periods.
[104]
Hogg, 1941, 407;
Pringle, 1988, 178.
[105]
Hogg, 1941, 387;
O’Rahilly and Müller, 2001, 169.
[106]
Pringle, 1988, 176.
[107]
O’Rahilly and Müller, 2001, 87: “It has been estimated that more than 90% of the more than 4500 named structures of
the adult body become apparent during the embryonic period (O’Rahilly).“
Page 11
The fetal period continues until birth.
By 9 weeks, thumb sucking begins[108] and the fetus can swallow amniotic fluid.[109]
The fetus can also grasp an object,[110] move the head forward and back, open and close the jaw, move the tongue, sigh,[111] and stretch.[112]
Nerve receptors in the face, the palms of the hands, and the soles of the feet can sense light touch.[113]
"In response to a light touch on the sole of the foot," the fetus will bend the hip and knee and may curl the toes.[114]
The eyelids are now completely closed.[115]
In the larynx, the appearance of vocal ligaments signals the onset of vocal cord development.[116]
In female fetuses, the uterus is identifiable[117] and immature reproductive cells called oogonia (ō-ō-gō′nē-ă) are replicating within the ovary.[118]
External genitalia begin to distinguish themselves as either male or female.[119]
Eseera eyitibwa 'fetal period' kyeyongera mumaso baka nga omwana azalidwa
Mu wiki mwende okumunakwengalo gutandika 'fetus'eyiza okummya amaazi aga 'amniotic fluid'.
Eyinza no'kukwata ebintu oba ekimju, oba ne oku tambuza omutwe mumaso ne'mabega, okugulawo no'kugalawo oluba, okutambuza olulimui no kwe golola.
Okufuna obusimu kumaso me mubibatu bwe mikono, ne wansi webigere biwulira ekibi konako.
"Singa wabowo okukwattibwa ko wansi webigere", 'fetus'ewetamu evivi okwo sako me bugere obutono.
Ebiwawo bya'maso biba bigale kukisere kino.
Mu larynx oba mu dokooli , obuwuzi obuvamu amalobozi butandika okulabika eraga okutandika okwokula kwa bu vocal cord'.
Mubawala 'fetus'oyiza okulaba 'uterus' oba nabana no obuggi obuto oba'reproductive cell' emto obuyitibwa 'oogania', zibamu mu óvary'ngazi gegenya enku.
Ebitundu ebyekyama bitandika okwelaga oba bisaaja oba bikaazi.
A burst of growth between 9 and 10 weeks increases body weight by over 75 percent.[120]
By 10 weeks, stimulation of the upper eyelid causes a downward rolling of the eye.[121]
The fetus yawns and often opens and closes the mouth.[122]
Most fetuses suck the right thumb.[123]
Sections of intestine within the umbilical cord are returning to the abdominal cavity.[124]
Ossification is underway in most bones.[125]
Fingernails and toenails begin to develop.[126]
Unique fingerprints appear 10 weeks after fertilization. These patterns can be used for identification throughout life.[127]
Wakatiwa wiiki omwenda ne kumi okukula kweyo ngere dalannyo nyini okuzito bwo mubiri bwe yongera paka ebitundu 75%.
Mu wiiki kumi ebibib kaamaso wagulu bitandikiriza okutambula mpola kino kiiletala amaso kutandika okwevunula oba okwekyusa ngagada wansi.
Waberayo okekyusa kwa 'fetus' era ne akamwa ko'mwana kegula era ne kegala.
Okusingira dala engalo ensaaja eya dyo enunibwa.
Ebitundu bwe'kyenda mu kundu eto oba oluseke omwana omwafunila emere ne bitu ebilala biba bidayo mukitundu kya wansi ekyo'mubiri oba 'abdominal cavity'.
Emitendera egiyitibwa okukula amagumba giba gigenda mumaso kakano.
Enjala ze bigere ne'ze'galo zitandika okukula.
Mugalo mweyoleka 'fingerprints' okuvanyu lwa wiiki kumi nga 'fertilization' awede. Zimo 'fingerprints' oba ebye kumu biyiza okukozesebwa okwa omuntu ono mubulamu bwe bwo .
By 11 weeks the nose and lips are completely formed.[128] As with every other body part, their appearance will change at each stage of the human life cycle.
The intestine starts to absorb glucose and water swallowed by the fetus.[129]
Though sex is determined at fertilization, external genitalia can now be distinguished as male or female.[130]
Wiiki kumi ne'mu weziwerera enyindo na'maso gabagamale okukulira dala. Nga ne bitundu ebilala ebyo'mubiri, engere gebifanana ekyuka nga omwana akula era ne mubulamu bwe bwo.
Ekyenda kitandiika okunyunyunta sukali (glucose) na'maazi bino bimilwa 'fetus'.
Newakubade obuwla obaobulenzi bwo'mwana bukasibwa nga 'fertilization' ebaddewo, ebitundu byekyama ebyawabweru kakati bimanyi bya era bilabike oba mulenzi oba muwala.
[108]
Liley, 1972, 103.
[109]
Campbell, 2004, 24;
de Vries, 1982, 311;
Petrikovsky et al., 1995, 605.
[110]
Robinson and Tizard, 1966, 52;
Valman and Pearson, 1980, 234.
[111]
de Vries et al., 1982, 305-307.
[112]
de Vries et al., 1982, 311.
[113]
Humphrey, 1964, 96;
Humphrey, 1970, 16-17 (cited by Reinis and Goldman,
1980, 232);
Humphrey and Hooker, 1959, 77-78.
[114]
Robinson and Tizard, 1966, 52;
Quote from Valman and Pearson, 1980, 234.
[115]
Andersen et al., 1965, 648-649;
O’Rahilly and Müller, 2001,
465; Pearson, 1980, 39-41.
[116]
O’Rahilly and Müller, 1984, 425. See also Campbell, 2004, 29.
[117]
O’Rahilly, 1977a, 128;
O’Rahilly, 1977b, 53;
O’Rahilly and Müller, 2001, 327.
[118]
O’Rahilly and Müller, 2001, 25 & 322.
[119]
Campbell, 2004, 28 & 35;
O’Rahilly and Müller, 2001, 336.
[120]
Brenner et al., 1976, 561.
[121]
Goodlin, 1979, D-128;
Humphrey, 1964, 102.
[122]
de Vries et al., 1982, 309.
[123]
Hepper et al., 1991, 1109.
[124]
Grand et al., 1976, 798;
Pringle, 1988, 178;
Sadler, 2005, 66;
Spencer, 1960, 9. [Pringle reports the bowel returns into the abdomen during the ninth or tenth week.]
[125]
Cunningham et al., 2001, 133.
[126]
O’Rahilly and Müller, 2001, 170-171.
[127]
Babler, 1991, 95;
Penrose and Ohara, 1973, 201;
For an overview of ridge formation in the skin of the hands see Cummins, 1929.
[128]
Timor-Tritsch et al., 1990, 291.
[129]
Koldovský et al., 1965, 186.
[130]
O’Rahilly and Müller, 2001, 336;
Wilson, 1926, 29.
Page 12
Between 11 and 12 weeks, fetal weight increases nearly 60 percent.[131]
Twelve weeks marks the end of the first third, or trimester, of pregnancy.
Distinct taste buds now cover the inside of the mouth. By birth, taste buds will remain only on the tongue and roof of the mouth.[132]
Bowel movements begin as early as 12 weeks and continue for about 6 weeks.[133]
The material first expelled from the fetal and newborn colon is called meconium (mĭ-kō'nē-ŭm).[134] It is composed of digestive enzymes, proteins, and dead cells shed by the digestive tract.[135]
By 12 weeks, upper limb length has nearly reached its final proportion to body size. The lower limbs take longer to attain their ultimate proportions.[136]
With the exception of the back and the top of the head, the body of the entire fetus now responds to light touch.[137]
Sex-dependent developmental differences appear for the first time. For instance, female fetuses exhibit jaw movement more frequently than males.[138]
In contrast to the withdrawal response seen earlier, stimulation near the mouth now evokes a turning toward the stimulus and an opening of the mouth.[139] This response is called the "rooting reflex" and it persists after birth, helping the newborn find his or her mother's nipple during breastfeeding.[140]
The face continues to mature as fat deposits begin to fill out the cheeks[141] and tooth development begins.[142]
By 15 weeks, blood-forming stem cells arrive and multiply in the bone marrow. Most blood cell formation will occur here.[143]
Although movement begins in the 6-week embryo, a pregnant woman first senses fetal movement between 14 and 18 weeks.[144] Traditionally, this event has been called quickening.[145]
Wakati wa wiiki 11 ne wiiki 12, obuzito bwa 'fetus' byeyongera nga ebitundu nkaga kukimu.
Wiiki kumi nabiri ezisoka gwe'myezi esatu egikulembera mukukula kwo'mwana, oba omyezi ogwukusata nga omukaazi ali lubuto.
Bu 'buds' obwoku womerwa ebiri bwa butandiika okulabika mukamwa. Buno bu 'tastes buds' buberamu era busigaramu mukamwa omwana nga azalidwa bubera ku lulimi ne wagulu kukibuno.
Ekyenda kitandikiza okutambula ku wiiki nga kumi nabiri kuno okutambula kweyo ngerera dala okuma wiiki nga mukaaga.
Ebintunto ebisoka okuva mu 'fetus' ne'kyenda ekito biyitibwa 'meconium'. Bubamukalonda nga 'digestive enzymes', emere'zimba omubiri ne 'cells' mu 'digestive tract' oba umuduu gwe mere.
Ku wiiki kumi nabiri, obuwanvubwe mikono bubabutukiride enkomerero yabwo okugerageranyu no'mubiri. Amagulu gatwa ekisera kiwanuu ko okutuka wagalina okukoma mukukula kukisera kino.
Nga ojeko umugongo ne wagulo wo'mutwe , omubiri gwa 'fetus' kakano guwuliliza ngagu kwati dwako.
Obusaaja oba obukaali bulabika muneyisa bweyoleka omulundi ogusokera dala. Gambanga 'fetus' enkazi etandika okuzanyisa oluba emirundi mingiko okusinga mubalenzi
Okujako okugana okulabibwa amangu enyo akamwa katandika okuberanga akayulira okukwatibwako ebiba bigwetolode wabera okuwuliza kwebwetolode sako nokuyasama kwomumwa. Kuno okuwuliliza kiyitibwa 'rooting reflex' kino kigala wo neomwana bwazalibwa nekiyamba omwana okusanga ebbere lyanyi mu kuyonsa.
Mumaso mwongera okukuza namasavu gatandika okukungana mumaso negayaba mukulula kwa'matamu nokukula kwaimanya kitandika.
Mu wiiki kumi na'tano bu 'stem cells' obukola omusaayi bweyoleka nebwogera okukula mu busomyo bwa'magumba. Bu 'cells' bwomusaayi obusingi bujakukolebwa oba kuzalibwa muno mubusomyo.
Newankubade nga okuzanya obaokutambula kwo'mubiri kutandika ku wiiki mukaaga' mukaazi wolubuuto asuka okuwilira omwana nga yekusa wakati wa wiiki kuminanyane wiiki kumi namunana. Kino kimanyidwa bulijo nga 'quickning' oba okwanguwa.
[131]
Brenner, 1976, 561.
[132]
Lecanuet and Schaal, 1996, 3;
Miller, 1982, 169;
Mistretta and Bradley, 1975, 80.
[133]
Abramovich and Gray, 1982, 296;
Ramón y Cajal and Martinez, 2003, 154-155, report visualizing defecation (bowel movements) with ultrasound in utero in all 240 fetuses studied between 15 and 41 weeks [postmenstrual age].
[134]
O’Rahilly and Müller, 2001, 257;
For a description of meconium by Aristotle see Grand et al., 1976, 791.
[135]
Grand et al., 1976, 806.
[136]
Moore and Persaud, 2003, 105.
[137]
Lecanuet and Schaal, 1996, 2;
Reinis and Goldman, 1980, 232.
[138]
Hepper et al., 1997, 1820.
[139]
Mancia, 1981, 351.
[140]
Bates, 1979, 419.
[141]
Poissonnet et al., 1983, 7;
Poissonnet et al., 1984, 3: In a study of 488 fetuses, Poissonnet’s group found that adipose tissue (fat) appears in the face from 14 weeks postfertilization. By 15 weeks, fat appears in the abdominal wall, back, kidneys, and shoulders. By 16 weeks, fat is also present throughout the upper and lower limbs.
[142]
Pringle, 1988, 178. [Thirteenth week postfertilization]
[143]
Pringle, 1988, 179.
[144]
Sorokin and Dierker, 1982, 720;
Leader, 1995, 595: “Some pregnant women reported fetal flutters as early as 12 weeks (quickening).“ Women also tend to accurately
recognize fetal movement at earlier fetal ages during second and subsequent pregnancies as compared to first pregnancies.
[145]
Spraycar, 1995, 1479;
Timor-Tritsch et al., 1976, 70.
Page 13
By 16 weeks, procedures involving the insertion of a needle into the abdomen of the fetus trigger a hormonal stress response releasing noradrenalin, or norepinephrin (nor-ep'i-nef'rin), into the bloodstream.[146]
In the respiratory system, the bronchial tree is now nearly complete.[147]
A protective white substance, called vernix caseosa (ver'niks caseo'sa), now covers the fetus. Vernix protects the skin from the irritating effects of amniotic fluid.[148]
From 19 weeks fetal movement, breathing activity, and heart rate begin to follow daily cycles called circadian (ser-kā'dē-ăn) rhythms.[149]
Mu wiiki kumi na mukaga emitendera je'mpiso mubitundu ebwawansi ebya 'fetus' kino kisikiza 'hormone' Eyuliza kununyigiribwa evako okuja kwa 'noradrenaline' Oba 'norepinepherine' mumusaayi. Abawere na'bakulu bona kino kibaukako okukyusiza dala emitendera ge twolede.
Mukusa kwo'mubiri, umudumu oguyitamu empewo kukisera kino guba gukulidedala.
Era ngeyo'mubiri ogwa langi ejeru oguziza akabi oba ogwokuma, oguyitibwa 'vernix caseosa' gubera gubise 'fetus' oba omwana akula mulubuto. Olususu lukumibya 'vernix' kubintu ebindi lutawanyiza nu kisera kino mu maazi aga 'amniotic fluid' omwana wiwaba.
Okuva wiiki kuminamwenda okukyuka kwa 'fetus' oba omwana no kussa, okwo no kukuba kwo'mutima 'gujandi okukuba munge'yejawulo buli lukya kino kiwitibwa 'circadian rythms' mululimi lwa bioligia
By 20 weeks the cochlea, which is the organ of hearing, has reached adult size[150] within the fully developed inner ear. From now on, the fetus will respond to a growing range of sounds.[151]
Hair begins to grow on the scalp.
All skin layers and structures are present, including hair follicles and glands.[152]
By 21 to 22 weeks after fertilization, the lungs gain some ability to breathe air.[153] This is considered the age of viability because survival outside the womb becomes possible for some fetuses.[154]
Mu wiiki abiri ekitundu kyo'kutu ekiyitibwa 'cochlea', ekikola kukuwulira, kiba kimaliza okukula era kimale okwetuka munda yo'kutu. Okuva kakati no kweyongerayo, 'fetus'oba omwana ayongera kuwulira amalobozi.
Enviri zitandika okukula Kukawompo.
Olususu kakati lubalwetuse, okwosaako ne'milandira genu mumubiri 'gland'.
Mu wiiki nga biri mwe'mu ne abiri ewede, amawugwe gafuna obusobolibwokusa omuka. Kino kiyitibwa okwetuka oba 'age of viability' mululimi lwa sayansi kubanga obulamu wabweru olubuuto buba bukakati busoboka mumwana omuwere oba 'fetus.' Emwaka mingi mukukulakulana bu bye'dagala ne sayansi bitandewo obusobozi kuyimirizawo'bulamu obwa'bawere azalibwanga.
[146]
Giannakoulopoulos et al., 1999, 494 & 498-499;
Glover and Fisk, 1999, 883;
Smith et al., 2000, 161. Cortisol levels also rise after invasive procedures following 21 weeks postfertilization - see Giannakoulopoulos et al., 1994, 80.
[147]
DiFiore and Wilson, 1994, 221-222;
Pringle, 1988, 178. [There is some disagreement among experts regarding when the bronchial tree is complete. Some say completion occurs as early as 16 weeks postfertilization while others say it occurs after birth.]
[148]
Campbell, 2004, 48;
Moore and Persaud, 2003, 107;
O’Rahilly and Müller, 2001, 168.
[149]
de Vries et al., 1987, 333;
Goodlin and Lowe, 1974, 349;
Okai et al., 1992, 391 & 396;
Romanini and Rizzo, 1995, 121;
For a description of the circadian system, see Rosenwasser, 2001, 127;
From Vitaterna et al., 2001, 92: Glossary: “Circadian: A term derived from the Latin phrase “circa diem,“ meaning “about a day;“ refers to biological variations or rhythms with a cycle of approximately 24 hours.“
[150]
Lecanuet and Schaal, 1996, 5-6;
Querleu et al., 1989, 410.
[151]
Glover and Fisk, 1999, 882;
Hepper and Shahidullah, 1994, F81;
Querleu et al., 1989, 410;
Sorokin and Dierker, 1982, 725 & 730;
Valman and Pearson, 1980, 233-234.
[152]
Pringle, 1988, 180.
[153]
Hansen and Corbet, 1998, 542.
[154]
O’Rahilly and Müller, 2001, 92, report the age of viability as 20 weeks postfertilization; Draper et al., 1999, 1094, report a survival rate of 2% at 20 weeks postfertilization, 6% at 21 weeks, and 16% at 22 weeks. Moore
and Persaud, 2003, 103, report viability at 22 weeks;
Wood et al., 2000, 379, report survival rates of 11% at 21 weeks, 26% at 22 weeks and 44% at 23 weeks (postfertilization weeks) based on premature birth data from the United Kingdom during 1995. Cooper et al. 1998, 976, (Figure 2) report infants with a birth weight over 500 grams experienced survival rates (all approximate) of 28% at 21 weeks postfertilization, 50% at 22 weeks, 67% at 23 weeks, and 77% at 24 weeks. Draper et al., 2003, updated their previously published survival tables for premature infants and now report an overall survival rate of 7% at 20 weeks, 15% at 21 weeks, 29% at 22 weeks, 47% at 23 weeks and 65% at 24 weeks. [All ages corrected to reflect postfertilization age.] These survival tables are available online at http://bmj.bmjjournals.com/cgi/content/full/319/7217/1093/DC1. Their methodology is described in their earlier paper (Draper et al., 1999, 1093-1094.) Note: These published survival tables reflect postmenstrual ages. Hoekstra et al., 2004, e3, report a survival rate of 66% at 23 weeks and 81% at 24 weeks “gestational age“ [not specifically defined] for premature births from 1996 to 2000 at their center in Minneapolis, Minnesota.
Page 14
By 24 weeks the eyelids reopen[155] and the fetus exhibits a blink-startle response.[156] This reaction to sudden, loud noises typically develops earlier in the female fetus.[157]
Several investigators report exposure to loud noise may adversely affect fetal health. Immediate consequences include prolonged increased heart rate, excessive fetal swallowing, and abrupt behavioral changes.[158] Possible long-term consequences include hearing loss.[159]
The fetal respiratory rate can rise as high as 44 inhalation-exhalation cycles per minute.[160]
During the third trimester of pregnancy, rapid brain growth consumes more than 50 percent of the energy used by the fetus. Brain weight increases between 400 and 500 percent.[161]
By 26 weeks the eyes produce tears.[162]
The pupils respond to light as early as 27 weeks.[163] This response regulates the amount of light reaching the retina[164] throughout life.
All components required for a functioning sense of smell are operational. Studies of premature babies reveal the ability to detect odors as early as 26 weeks after fertilization.[165]
Placing a sweet substance in the amniotic fluid increases the rate of fetal swallowing. In contrast, decreased fetal swallowing follows the introduction of a bitter substance. Altered facial expressions often follow.[166]
Through a series of step-like leg motions similar to walking, the fetus performs somersaults.[167]
The fetus appears less wrinkled as additional fat deposits form beneath the skin.[168] Fat plays a vital role in maintaining body temperature and storing energy after birth.
Mu wiiki abiri munya amaaso gegula-nate omwana oba 'fetus' natandika okutemyatemya. Bikula mangunyo mubana abowela.
Abanonyerela kubya sayansi bagambanti amalobozi agawagule enyo gayiza okusa obulamu omwana bwi 'fetus' obubi. Amangu dala ekivamwekyo omutima gwo'mwana 'fetus' okwewonge okuba nyo okuva kubwegulina okuba omwana 'fetus' okwongera okumira okwo sako no kukyuka muneyia. No mwana 'fetus' auinza okufuna obuzibu mukuwulira okweyionge'nyo.
Era no kusa kwe kuyinza okweyonge'nyo nga emirundi ana mutenaeto kuyingiza no kufulumya empewo buli dakika.
Emyezi esatu egikomekerera nga omukaazi ali lubuto okukula kwo'bwongo amangu dala kutawala ebitundi 50% ebya'manyi mumubiri akozesebwa omwana 'fetus'. Obuzito bwo'bwongo bweyonge w'ebitundu ebikumi 400 ne 500%.
Oluvanyu lwa wiiki abiri mumukana amaso gaja amaziga.
Ekitundu kwamasozi ekiyibwa enjuba oba 'pupil' kitandika okukyuka mutaala oba ekitanga mu wiiki 27. Kino kiyamba okugera omuyendo gwe kitanga oba etaala ekiyingi mukitundu ekya 'retina' mubulamu bwona obwa 'muntuoyo'.
Buli kintu ekyetagisa mukuwanyiriza kibanakyo kikola bulungi. Emisomo ejikwata ku abaana abawere atanaba ketuka kigamba bau obusibozi obwoku wunyiriza oluvanyuma lwa wiiki abiri mumukaga nga 'fertilization' oba okumwaka kuwede.
Singa ekituwa oba otuzi otuwomerera kutekebwa mumaazi omwana mwakulira 'amniotic fluid' omwana yeyongera okumira. Ate okumira kukedera nga ekintu oba amaazi agakawa gegatekebwamu. Era omwana alabika yenyinyibala mumasoge.
Mugeri yokubanga ayagalaokutambula ekyandibade nga okutambu omwana otandika okwefula.
Era omwana alabika nga olukanyanya olumugwako nga egeri wolu savusavu bwe lukungana wansi wolususu. Amasavu gano gamugasonyo. Okulaba nga okubuguma kwomubiri kwa kigero era nga kweku sanide era gega kuma ne amanyi nga omwana azalidwa.
[155]
Open eyes are visualized by 4D ultrasound following 22 weeks postfertilization per Campbell 2002, 3; De Lia, 2002, personal communication;
O’Rahilly and Müller, 2001, 465. For a detailed ultrastructural study of the union between the upper and lower eyelids see Andersen et al., 1967, 293.
[156]
Birnholz and Benacerraf, 1983, 517 (cited by Drife, 1985, 778);
See also Campbell, 2002, 3: Professor Stuart Campbell correctly points out that the eyes of the fetus are closed most of the time and a true blink requires the eyes to be open. Perhaps the “blink-startle“ response would be more accurately termed “squint-startle.“
[157]
Lecanuet and Schaal, 1996, 9.
[158]
Visser et al., 1989, 285.
[159]
Gerhardt, 1990, 299;
Petrikovsky et al., 1993, 548-549;
Pierson, 1996, 21 & 26.
[160]
Natale et al., 1988, 317.
[161]
Growth of the human brain, 1975, 6;
Mancuso and Palla, 1996, 290.
[162]
Isenberg et al., 1998, 773-774.
[163]
Robinson and Tizard, 1966, 52.
[164]
Noback et al., 1996, 263.
[165]
Lecanuet and Schaal, 1996, 3.
[166]
Lecanuet and Schaal, 1996, 3;
Liley, 1972, 102;
Moore and Persaud, 2003, 219;
Reinis and Goldman, 1980, 227.
[167]
Liley, 1972, 100.
[168]
England, 1983, 29.
Page 15
By 28 weeks the fetus can distinguish between high- and low-pitched sounds.[169]
By 30 weeks, breathing movements are more common and occur 30 to 40 percent of the time in an average fetus.[170]
During the last 4 months of pregnancy, the fetus displays periods of coordinated activity punctuated by periods of rest. These behavioral states reflect the ever-increasing complexity of the central nervous system.[171]
Mu wiiki 28 omwana kakati asobola okwawula wakati wa edobozi lwawagulu newansi.
Mu wiiki 30okusa kuba kutandise okulabika era kubawo wakati webitundi 30- 40% okutukka kubintu ana bye saawa.
Mu mwezi ena egisembayo omukaazi nga ali lubuuto, wabelawo ekisera omwana bwa kyuka oba bwakola abitintu mungeri etegerekeka oluvanyuma era awumulako. Eneyisa eno eraga nti omwana abade weyongera okukula bukula bulikisera mubusimu obwawakati 'central nervous system'.
By approximately 32 weeks, true alveoli (al-vē'ō-lī), or air "pocket" cells, begin developing in the lungs. They will continue to form until 8 years after birth.[172]
At 35 weeks the fetus has a firm hand grasp.[173]
Fetal exposure to various substances appears to affect flavor preferences after birth. For instance, fetuses whose mothers consumed anise, a substance which gives licorice its taste, showed a preference for anise after birth. Newborns without fetal exposure disliked anise.[174]
Mu wiiki nga asantu mubiri obusenge bwempewo oba 'alveoli' oba obusenge empewoesibwamwe mwenda, butandika okukula mumawugwe. Era bwewone okukula okutuki dala kumwaka 8 omwana ga amaze okuzalibwa.
Mu wiiki 35 omwana aba atandise okunyweza ebintu mungalo ze.
Omwana asisinka ebintu bingi gabanga emere amaazi ne kalunda omulala owomugaso jail bino bimusaaliwo ebintu yaga oba byata yagale nga'zalidwa. Gamba nga abuba maama abakuzesa enyo ebintu nga 'anise', ekintu ekiwa 'licorise' empoma abana bano bawaa okwagala kwa 'anise' nga bazalidwa. Abawere atasisinkana 'anise' mulubuuto bab tebamuugala
The fetus initiates labor[175] by releasing large amounts of a hormone called estrogen (es´trō-jen)[176] and thus begins the transition from fetus to newborn.
Labor is marked by powerful contractions of the uterus, resulting in childbirth.[177]
From fertilization to birth and beyond, human development is dynamic, continuous, and complex. New discoveries about this fascinating process increasingly show the vital impact of fetal development on lifelong health.
As our understanding of early human development advances, so too will our ability to enhance health––both before and after birth.
Omwana alaga obubonero bwo kwaga ozalibwa kino akiko nga afulumiya 'hormone' eno eyitibwa 'estrogen' era ekyukakyuka okuva mwana omulubuuto okugenda ku mwana omuwere.
Kukisera kino nabaana atandiika okulago obubonero obwo kufulumya omwana, kino kyekivako okuzalibwa kwo'mwana.
Okuva muku waka 'fertilization' okutuka kukuzalibwa kwo'mwana no kweyonge, ekulakulana yomubiri yamungeri nyigi era genda mumaasi buli enukusifu. Ebipya ebisangidwa ebikwaku mitendre gino ejewunyisa nga okukula kwo'mwana munda yanyi bwekuli okululu enyo mukubera kwomuntu mubuwamu kunzi eno.
Nga etegera yaffe eyokulala kwo'muntu mubisera bisokerwako bwetuna yongera okukulakula nya no kulogosa embere yo bulamu bwaffe nga omwana tana kuzalibwa ne bwaba azalidwa.
[169]
Glover and Fisk, 1999, 882;
Hepper and Shahidullah, 1994, F81.
[170]
Connors et al., 1989, 932;
de Vries et al., 1985, 117;
Patrick et al., 1980, 26 & 28;
Visser et al., 1992, 178.
[171]
DiPietro et al., 2002, 2: “One of the hallmarks of development before birth is the coalescence of patterns of fetal and behavioral and cardiac function into behavioral states, which is widely viewed as reflective of the developing integration of the central nervous system.“
[172]
Lauria et al., 1995, 467.
[173]
Moore and Persaud, 2003, 108.
[174]
Schaal et al., 2000, 729.
[175]
Liley, 1972, 100.
[176]
Moore and Persaud, 2003, 131.
[177]
Cunningham et al., 2001, 252.
Page 16
Given:
1. The DNA molecule measures 3.4×10-9 meters per 10 base pairs.[178]
2. There are 3 billion (3×109) base pairs per cell.
3. There are an estimated 100 trillion (1014) cells per adult.
4. The distance from the earth to the sun is approximately 93 million miles.
5. There are 2.54 centimeters (cm) per inch.
Step 1 Compute the length of DNA in a single cell:
3.4×10-9 meters/10 base pairs × 3×109 base pairs/cell = 1.02 meters of DNA per cell
Step 2 Compute the total length of DNA in an adult’s 100 trillion cells:
1.02 meters of DNA/cell × 1014 cells = 1.02×1014 meters of DNA per adult*
Step 3 Convert 1.02×1014 meters to miles:
1.02×1014 meters × 100 cm/meter × 1inch/2.54 cm × 1 foot/12 inches × 1 mile/5,280 feet
= 6.3379×1010miles of DNA
Step 4 Compute how many round trips from the earth to the sun:
6.3379×1010 miles of DNA ÷ (93,000,000 miles/trip × 2 trips/round trip) =
Therefore, the DNA in a single adult, if oriented in linear fashion, would exceed 63 billion miles in length. This is long enough to extend from the earth to the sun and back––340 times.
* Approximately 25 trillion red blood cells are present in the adult.[179] It should be noted that red blood cells contain DNA early in their maturation phase but this DNA degenerates and is not present in the mature form. This calculation includes the DNA from red blood cells.
[178]
Lodish et al., 2000, 104.
[179]
Guyton and Hall, 2000, 2.
Page 17
The following page contains a list of 3,808 capital letters each of which represents a single base.
Given:
1. A, G, T, and C each represent a base within the DNA of a single cell.
2. Each line contains 68 letters without spaces representing 68 bases.
3. Each page contains 56 lines. (Page size: 8½ × 11 inches, font: Times New Roman, font size: 10, spaces between letters: none, lines: single spaced, margins: as shown)
4. Each cell contains 3 billion base pairs equaling 6 billion bases.
The calculation of the number of pages required to list all DNA bases in a single cell is as follows:
68 bases/line × 56 lines/page = 3,808 bases/page
6,000,000,000 bases/cell ÷ 3,808 bases/page = 1,575,630 pages/cell
Page 18
Given:
1. The placenta maintains embryonic and fetal temperature between 0.5 ºC and 1.5 ºC above maternal core temperature.[180]
2. Maternal core temperature is approximately 99.6º Fahrenheit.
3. The formula to convert temperature from Fahrenheit (ºF) to Celsius (ºC) is:
ºC = 5/9 (ºF - 32)
The calculation to compute the range of embryonic and fetal body temperature is as follows:
Step 1 Convert maternal core temperature to Celsius:
Maternal core temperature in ºC: ºC = 5/9 (99.6 - 32) = 37.56 ºC
Step 2 Compute lower and upper ranges of fetal body temperature in Celsius:
Lower range (Celsius) = maternal core temperature + 0.5 ºC = 37.56 + 0.5 = 38.2 ºC
Upper range (Celsius) = maternal core temperature + 1.5 ºC = 37.56 + 1.5 = 39.2 ºC
Step 3 Convert results to Fahrenheit:
ºC = 5/9 (ºF - 32) 9/5 ºC = (ºF - 32) ºF = 9/5 ºC + 32
Substituting to find the lower limit of fetal body temperature
ºF = 9/5 ºC + 32 ºF = 9/5 (38.16) + 32 ºF = 100.7º
Substituting to find the upper limit of fetal body temperature
ºF = 9/5 ºC + 32 ºF = 9/5 (39.16) + 32 ºF = 102.5º
Summary of Normal Embryonic and Fetal Body Temperature Range
ºF | ºC | |
---|---|---|
Lower Limit | 100.7 | 38.2 |
Upper Limit | 102.5 | 39.2 |
Page 19
The Embryonic Period
Various authors agree the heart rate peaks at 7 weeks. Reported heart rates vary however. Van Heeswijk et al. report a peak heart rate of 167 ± 8 beats per minute (bpm)[181] while Leeuwen et al. report a peak rate of 175 bpm.[182] Van Lith et al. report the median fetal heart rate peaks at 177 bpm at 7 weeks.[183] One hundred seventy (170) bpm has been chosen as the peak heart rate for illustration purposes in this calculation. The heart rate for the various weeks from 7 through 38 have been calculated via linear interpolations[184] assuming heart rates of 170 bpm at 7 weeks and 140 bpm at term or 38 weeks.[185]
(Note: Heart rates are estimated. Living conditions and individual experience can and will vary.)
The Fetal Period
Week # | Average Heart Rate (Beats per Minute) |
Beats per Week | Running Total |
---|---|---|---|
9 | 168.06 | 1,694,090 | 9,103,216 |
10 | 167.10 | 1,684,336 | 10,787,551 |
11 | 166.13 | 1,674,581 | 12,462,132 |
12 | 165.16 | 1,664,826 | 14,126,958 |
13 | 164.19 | 1,655,071 | 15,782,029 |
14 | 163.23 | 1,645,316 | 17,427,346 |
15 | 162.26 | 1,635,562 | 19,062,907 |
16 | 161.29 | 1,625,807 | 20,688,714 |
17 | 160.32 | 1,616,052 | 22,304,766 |
18 | 159.35 | 1,606,297 | 23,911,063 |
19 | 158.39 | 1,596,542 | 25,507,605 |
20 | 157.42 | 1,586,787 | 27,094,393 |
21 | 156.45 | 1,577,033 | 28,671,425 |
22 | 155.48 | 1,567,278 | 30,238,703 |
23 | 154.52 | 1,557,523 | 31,796,226 |
24 | 153.55 | 1,547,768 | 33,343,994 |
25 | 152.58 | 1,538,013 | 34,882,008 |
26 | 151.61 | 1,528,259 | 36,410,266 |
27 | 150.65 | 1,518,504 | 37,928,770 |
28 | 149.68 | 1,508,749 | 39,437,519 |
29 | 148.71 | 1,498,994 | 40,936,513 |
30 | 147.74 | 1,489,239 | 42,425,752 |
31 | 146.77 | 1,479,484 | 43,905,237 |
32 | 145.81 | 1,469,730 | 45,374,966 |
33 | 144.84 | 1,459,975 | 46,834,941 |
34 | 143.87 | 1,450,220 | 48,285,161 |
35 | 142.90 | 1,440,465 | 49,725,626 |
36 | 141.94 | 1,430,710 | 51,156,337 |
37 | 140.97 | 1,420,956 | 52,577,292 |
38 | 140.00 | 1,411,201 | 53,988,493 |
(Approximately 54 million beats before birth) |
Counting the Beats of a Lifetime
The Postnatal Period from Birth to 80 Years
Year # | Average Heart Rate (Beats per Minute)*[186] |
Beats per Year | Running Total |
---|---|---|---|
1 | 120 | 63,115,200 | 63,115,200 |
2 | 110 | 57,855,600 | 120,970,800 |
3 | 103 | 54,173,880 | 175,144,680 |
4 | 103 | 54,173,880 | 229,318,560 |
5 | 103 | 54,173,880 | 283,492,440 |
6 | 103 | 54,173,880 | 337,666,320 |
7 | 95 | 49,966,200 | 387,632,520 |
8 | 95 | 49,966,200 | 437,598,720 |
9 | 95 | 49,966,200 | 487,564,920 |
10 | 95 | 49,966,200 | 537,531,120 |
11 | 85 | 44,706,600 | 582,237,720 |
12 | 85 | 44,706,600 | 626,944,320 |
13 | 85 | 44,706,600 | 671,650,920 |
14 | 85 | 44,706,600 | 716,357,520 |
15 | 80 | 42,076,800 | 758,434,320 |
16 | 80 | 42,076,800 | 800,511,120 |
17 | 75 | 39,447,000 | 839,958,120 |
18 | 75 | 39,447,000 | 879,405,120 |
19 | 70 | 36,817,200 | 916,222,320 |
20 | 70 | 36,817,200 | 953,039,520 |
21-80 | 70 | 2,209,032,000 | 3,162,071,520 |
(Approximately 3.16 billion beats from birth to age 80 years) | |||
Estimated Total Heart Beats From the 3-Week Embryo to Age 80 Years |
3,216,060,000 | ||
(Approximately 3.2 Billion Beats Per Lifetime) |
[181]
van Heeswijk et al., 1990, 153.
[182]
Leeuwen et al., 1999, 265.
[183]
van Lith et al., 1992, 741.
[184]
See Appendix A.
[185]
DiPietro et al., 1996, 2559.
[186]
Age appropriate pediatric heart rates adapted from Bates, 1987, 541.
Page 20
O'Rahilly and Müller's Age Assignments vs. Carnegie Stages, 1987 to 2001
Carnegie Stage |
Number of Somites |
Greatest Length (mm) |
1987 Age [187] Convention (in PF Days*) |
1999 Age [188] Convention (in PF Days*) |
2001 Age [189] Convention (in PF Days*) |
---|---|---|---|---|---|
1 | 0.1 - 0.15 | 1 | - | 1 | |
2 | 0.1 - 0.2 | 1½ - 3 | 2 - 3 | 2 - 3 | |
3 | 0.1 - 0.2 | 4 | 4 - 5 | 4 - 5 | |
4 | 0.1 - 0.2 | 5 - 6 | 6 | 6 | |
5 | 0.1 - 0.2 | 7 - 12 | 7 - 12 | - | |
5a | 0.1 | 7 - 8 | - | 7 - 8 | |
5b | 0.1 | 9 | - | 9 | |
5c | 0.15 - 0.2 | 11 - 12 | - | 11 - 12 | |
6 | 0.2 | 13 | 17 | 17 | |
6a | - | - | - | - | |
6b | - | - | - | - | |
7 | 0.4 | 16 | 19 | 19 | |
8 | 1.0 - 1.5 | 18 | 23 | - | |
8a | - | - | - | 23 | |
8b | - | - | - | 23 | |
9 | 1-3 | 1.5 - 2.5 | 20 | 26 | 25 |
10 | 4-12 | 2 - 3.5 | 22 | 29 | 28 |
11 | 13-20 | 2.5 - 4.5 | 24 | 30 | 29 |
12 | 21-29 | 3 - 5 | 26 | 31 | 30 |
13 | 30+ | 4 - 6 | 28 | 32 | 32 |
14 | 5 - 7 | 32 | 33 | 33 | |
15 | 7 - 9 | 33 | 35 | 36 | |
16 | 8 - 11 | 37 | 37 | 38 | |
17 | 11 - 14 | 41 | 40 | 41 | |
18 | 13 - 17 | 44 | 42 | 44 | |
19 | 16 - 18 | 47½ | 44 | 46 | |
20 | 18 - 22 | 50½ | 47 | 49 | |
21 | 22 - 24 | 52 | 50 | 51 | |
22 | 23 - 28 | 54 | 52 | 53 | |
23 | 27 - 31 | 56½ | 56 | 56 |
* PF Days = Postfertilization Days
There is international agreement among embryologists that human development during the embryonic period be divided into 23 stages (which were initially proposed by Mall, described by Streeter, and amended by O'Rahilly and Müller in 1987).[190] These have come to be known as Carnegie Stages. Particular internal and external features are required for inclusion in any given embryonic stage. These stages are independent of age and length and the use of the term 'stage' should be reserved for reference to this system per O'Rahilly and Müller in multiple publications.
Along with nearly-universal acceptance of the human embryonic staging system, a variety of age assignments have been proposed for each embryonic stage. Streeter believed the embryonic period spanned a 47- to 48-day period instead of the 56-day period accepted today. The Endowment for Human Development adopts the convention set forth by O'Rahilly and Müller in 1987 which has received widespread, but not universal, acceptance. O'Rahilly and Müller have since proposed amending this convention in light of transvaginal ultrasound data through a personal communication with Dr. Josef Wisser in 1992.[191] These alternate proposals are provided for the interested reader.
For instance, the onset of embryonic cardiac contraction (onset of the heartbeat) has long been described as a Carnegie Stage 10 or possibly a late Stage 9 event.[192] We report this event occurring at an age of 3 weeks, 1 day (22 days) postfertilization using the 1987 convention. Others may report this occurrence at 28 or 29 days as shown above. Of interest is a paper by Wisser and Dirschedl who reported using transvaginal ultrasound to visualize the embryonic heartbeat 23 days postfertilization in two embryos fertilized in vitro “with exactly known … age” and “in embryos from 2 mm of greatest length onwards.”[193] This finding most closely coincides with the 1987 age convention. Schats et al. reported the earliest cardiac activity at 25 days after follicle aspiration in embryos conceived in vitro.[194] Tezuka et al. reported the earliest cardiac activity at 23 days postfertilization in embryos conceived naturally.[195]
There is considerable variation in normal human development during the postnatal period. The prenatal period is no different with variations in the size, rate of growth, and order of appearance of some structures or functions. No one knows the exact age range for each stage with absolute certainty. These approximations may change in the future as additional knowledge is gained through careful, published research.
[187]
O'Rahilly and Müller, 1987, 3. Greatest length data is essentially uniform throughout the various texts.
[188]
O'Rahilly and Müller, 1999a. Various pages.
[189]
O'Rahilly and Müller, 2001, 490. Table A-1 – essentially unchanged from the 1996 edition. The 2001 convention
differs only slightly from the 1999 convention as shown.
[190]
O'Rahilly and Müller, 2001, 3.
[191]
O'Rahilly and Müller, 1999a, 13.
[192]
See footnote #51.
[193]
Quotes from Wisser and Dirschedl, 1994, 108.
[194]
Schats et al., 1990, 989.
[195]
Tezuka, 1991, 211.
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Page 27
Journal Abbreviation | Journal Name |
---|---|
Acta Anat | Acta Anatomica |
Acta Opthalmol | Acta Ophthalmologica |
Adv Contracept | Advances in Contraception |
Alcohol Res Health | Alcohol Research & Health |
Am J Anat | The American Journal of Anatomy |
Am J Cardiol | The American Journal of Cardiology |
Am J Kidney Dis | American Journal of Kidney Diseases |
Am J Obstet Gynecol | American Journal of Obstetrics and Gynecology |
Am J Reprod Immunol | American Journal of Reproductive Immunology and Microbiology |
Am J Respir Cell Mol Biol | American Journal of Respiratory Cell and Molecular Biology |
Am J Roentgenol | American Journal of Roentgenology |
Anat Embryol | Anatomy and Embryology |
Ann Otol Rhinol Laryngol | The Annals of Otology, Rhinology, and Laryngology |
Ann R Coll Surg Eng | Annals of the Royal College of Surgeons of England |
Arch Dis Child | Archives of Disease in Childhood |
Arch Ophthalmol | Archives of Ophthalmology |
Aust N Z J Psychiatry | The Australian and New Zealand Journal of Psychiatry |
Biol Neonate | Biology of the Neonate |
Birth Defects Orig Artic Ser | Birth Defects Original Article Series |
Br J Obstet Gynaecol | British Journal of Obstetrics and Gynaecology |
Br Med Bull | British Medical Bulletin |
Br Med J | British Medical Journal |
Chem Senses | Chemical Senses |
Child Dev | Child Development |
Clin Obstet Gynecol | Clinical Obstetrics and Gynecology |
Contrib Embryol | Contributions to Embryology |
Dev Med Child Neurol | Developmental Medicine and Child Neurology |
Dev Pharmacol Ther | Developmental Pharmacology and Therapeutics |
Early Hum Dev | Early Human Development |
Eur J Obstet Gynecol Reprod Biol | European Journal of Obstetrics, Gynecology, and Reproductive Biology |
Eye | Eye |
Facial Plast Surg | Facial Plastic Surgery |
Fertil Steril | Fertility and Sterility |
Fetal Ther | Fetal Therapy |
Gastroenterology | Gastroenterology |
Gynecol Invest | Gynecologic Investigation |
Gynecol Obstet Invest | Gynecologic and Obstetric Investigation |
Int J Psychoanal | The International Journal of Psycho-Analysis |
Ir J Med Sci | Irish Journal of Medical Science |
J Clin Ultrasound | Journal of Clinical Ultrasound |
J Comp Neurol | The Journal of Comparative Neurology |
J Med Genet | Journal of Medical Genetics |
J Comp Neurol | Journal of Neuroradiology |
J Pathol Bacteriol | The Journal of Pathology and Bacteriology |
J Pediatr Surg | Journal of Pediatric Surgery |
J Perinat Med | Journal of Perinatal Medicine |
J Anat | Journal of Anatomy |
JAMA | JAMA : The Journal of the American Medical Association |
Lancet | Lancet |
N Engl J Med | The New England Journal of Medicine |
N Z Med J | New Zealand Medical Journal |
Nature | Nature |
Neurology | Neurology |
Neuropsychologia | Neuropsychologia |
Nutr Rev | Nutrition Reviews |
Obstet Gynecol | Obstetrics & Gynecology |
Pediatr Pathol Lab Med | Pediatric Pathology & Laboratory Medicine |
Pediatr Res | Pediatric Research |
Pediatrics | Pediatrics |
Physiol Rev | Physiological Reviews |
Science | Science |
Semin Pediatr Surg | Seminars in Pediatric Surgery |
Semin Perinatol | Seminars in Perinatology |
Semin Reprod Endocrinol | Seminars in Reproductive Endocrinology |
Semin Roentgenol | Seminars in Roentgenology |
Teratology | Teratology |
Trans Am Neurol Assoc | Transactions of the American Neurological Association |
Ultrasound Obstet Gynecol | Ultrasound in Obstetrics & Gynecology |
Z Anat Entwicklungsgesch | Zeitschrift fur Anatomie und Entwicklungsgeschichte |
Page 28
A |
Page Links |
abdomen | 8, 9, 14 |
abdominal | 6, 12 |
activity | 10, 14, 16 |
adenine | 4 |
adult(s) | 3, 4, 10, 11, 14 |
age | 14 |
age of viability | 14 |
air | 11, 14, 16 |
alveoli | 16 |
amnion | 6, 7 |
amniotic fluid | 7, 11, 12, 14, 15 |
anise | 16 |
articular | 11 |
B |
|
base pairs | 17 |
base(s) | 4, 18 |
behavior(al) | 11, 15, 16 |
billion | 4, 7, 11 |
birth | 3, 6, 7, 11, 12, 13, 15, 16 |
blastocyst | 5 |
blink-startle | 15 |
blood | 4, 5, 6, 7, 9, 11, 13 |
blood cells | 6 |
blood vessels | 6, 11 |
blueprint | 4 |
body | 3, 4, 5, 6, 11, 12, 13, 15 |
body plan | 6 |
bone(s) | 6, 10, 11, 12, 13 |
bowel | 13 |
brain | 6, 7, 9, 11, 15 |
breastfeeding | 13 |
breathing | 9, 11, 16 |
bronchi | 8 |
bronchial tree | 14 |
buds | 7, 13 |
C |
|
cardiac | 16, 21 |
cardiovascular | 6 |
Carnegie Stage(s) | 3, 4, 5, 6, 7, 8, 9, 10, 21 |
cartilage | 6, 8 |
cell(s) | 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 16 |
central nervous system | 16 |
cerebral hemispheres | 7, 9 |
chambers | 6, 7 |
cheeks | 13 |
chest | 6, 10 |
childbirth | 16 |
chromosomes | 4 |
circulatory | 5, 6 |
clavicle | 10 |
close | 12 |
cochlea | 14 |
collar bone | 10 |
conception | 3 |
contraction | 16 |
cytosine | 4 |
D |
|
day(s) | 5, 6, 8, 10 |
development(al) | 3, 4, 6, 7, 9, 12, 13, 16 |
diaphragm | 9 |
digestive | 6, 13 |
distinguish(ed) | 12, 16 |
DNA | 4, 17, 18 |
E |
|
ear | 9, 14 |
early pregnancy factor (EPF) | 4 |
earth | 4, 17 |
ectoderm | 6 |
egg | 4 |
elbows | 10 |
electrocardiogram | 10 |
electrodes | 9 |
embryo | 3, 4, 5, 6, 7, 8, 9, 11, 13 |
embryology | 4 |
embryonic | 3, 4, 5, 7, 9, 11, 19, 20 |
embryonic period | 11, 20 |
encephalography | 9 |
endoderm | 6 |
energy | 15 |
enzymes | 13 |
epiblast | 6 |
epidermis | 11 |
estrogen | 16 |
extension | 11 |
eye(s) | 10, 11, 12, 15 |
eyelids | 10, 11, 12, 15 |
Page 29
F |
Page Links |
face | 11, 12, 13 |
Fallopian tubes | 4 |
fat | 13, 15 |
female | 10, 12, 13, 15 |
fertilization | 3, 4, 5, 6, 12, 14, 15, 16 |
fetal | 3, 5, 12, 13, 14, 15, 16 |
fetal period | 3, 12, 17 |
fetus | 3, 5, 6, 12, 13, 14, 15, 16 |
fingerprints | 12 |
fingers | 10 |
flattening | 9 |
fluid | 7, 11, 12, 14, 15 |
folding | 6 |
follicles | 14 |
forebrain | 6, 7 |
formation | 3, 8, 11, 12 |
function(s) | 3, 7, 21 |
fuse | 11 |
G |
|
genitalia | 12 |
germ cells | 8 |
germ layers | 6 |
gestational age | 3, 14 |
glands | 14 |
glucose | 12 |
grasp | 12, 16 |
grasping | 11 |
gravity | 11 |
grow(ing)(s) | 3, 5, 6, 9, 11, 14 |
growth | 6, 7, 10, 11, 12, 15 |
guanine | 4 |
H |
|
hair | 6, 11, 14 |
hand(s) | 8, 9, 10, 11, 12, 16 |
head | 5, 7, 9, 11, 12, 13 |
health | 15, 16 |
hearing | 7, 14, 15 |
hearing loss | 15 |
heart | 6, 7, 8, 10, 14, 15 |
heart rate | 14, 15, 20 |
heartbeat(s) | 20 |
helix | 4 |
hindbrain | 6, 7 |
hormone(s) | 5 |
hours | 4, 14 |
human | 3, 4, 5, 6, 11, 12, 16 |
human chorionic gonadotropin (hCG) | 5 |
hypoblast | 6 |
I |
|
implantation | 5 |
inner cell mass | 5, 6 |
intestine | 9, 12 |
J |
|
jaw | 10, 11, 12, 13 |
jaw movement | 11, 13 |
joints | 10, 11 |
Page 30
K |
Page Links |
kidneys | 6, 8, 11 |
knee | 10 |
L |
|
labor | 16 |
larynx | 12 |
learning | 7 |
left-handed | 11 |
leg | 15 |
licorice | 16 |
life cycle | 12 |
lifespan | 7 |
light | 12, 13, 15 |
limb(s) | 7, 11, 13 |
lips | 12 |
liver | 6, 8, 9 |
lungs | 8, 14, 16 |
lymphocytes | 9 |
M |
|
male | 11, 12, 13 |
man | 4 |
marrow | 13 |
maternal | 4, 5, 19 |
meconium | 13 |
medications | 5 |
memory | 7 |
menstrual cycle | 5 |
mesoderm | 6 |
metaphase | 4 |
meters | 17 |
midbrain | 6, 7 |
miles | 4, 17 |
million | 4, 7, 17 |
mitosis | 4 |
molecule(s) | 4, 17 |
morula | 5 |
mouth | 9, 11, 12, 13 |
move | 12 |
movement(s) | 7, 9, 10, 11, 13, 14, 16 |
mulberry | 5 |
muscle(s) | 6, 11 |
muscular | 11 |
N |
|
nails | 6 |
nerve(s) | 6, 11 |
neural | 11 |
neuromuscular | 9 |
newborn(s) | 11, 13, 14, 16 |
nipple(s) | 10, 13 |
noise | 15 |
noradrenaline | 14 |
norepinephrine | 14 |
nose | 12 |
O |
|
odors | 15 |
oocyte | 4 |
oogonia | 12 |
open(s) | 12, 13, 15 |
ossification | 10 |
ovaries | 4, 10 |
ovary | 4, 12 |
ovulation | 4 |
oxygen | 5 |
Page 31
P |
Page Links |
palms | 12 |
pancreas | 6 |
percent | 11, 12, 13, 15, 16 |
physiologic herniation | 9 |
placenta | 5, 19 |
postfertilization age | 9, 10, 13, 14, 15, 20 |
postmenstrual age | 3, 9, 13, 14 |
postnatal | 20 |
preference(s) | 11, 16 |
pregnancy | 3, 4, 5, 13, 15, 16 |
premature(ly) | 14, 15 |
prenatal | 21 |
problem-solving | 7 |
proportion | 13 |
protection | 7 |
pupils | 15 |
Q |
|
quickening | 13 |
R |
|
reflex | 13 |
reflexive(ly) | 9, 11 |
reopen | 15 |
reproductive | 4, 8, 12 |
respiratory | 6, 8, 14, 15 |
respond(s) | 13, 14, 15 |
response | 10, 12, 13, 14, 15 |
retina | 10, 15 |
right-hand | 11 |
rolling over | 11 |
roof | 13 |
rooting reflex | 13 |
rotation | 11 |
S |
|
sac | 6, 7 |
scalp | 14 |
sense(s) | 12, 13, 15 |
sex | 12 |
sigh | 12 |
skeletal | 11 |
skin | 6, 7, 11, 14, 15 |
skin layers | 14 |
sole(s) | 12 |
somersaults | 15 |
sounds | 14, 16 |
speech | 7 |
sperm | 4 |
spermatozoon | 4 |
spinal cord | 6 |
spontaneous | 9, 11 |
squinting | 11 |
startle | 10, 15 |
stem cells | 5, 13 |
stimulation | 12, 13 |
stress response | 14 |
stretch | 12 |
structure(s) | 3, 5, 6, 11, 14, 21 |
survival | 3, 14 |
swallow(ed)(ing) | 12, 15 |
system(s) | 3, 5, 6, 8, 9, 14, 16, 21 |
T |
|
taste | 13, 16 |
taste buds | 13 |
tears | 15 |
temperature | 5, 15, 19 |
testes | 11 |
testosterone | 11 |
thought | 7 |
thumb sucking | 12 |
thymine | 4 |
toes | 10, 12 |
tongue | 12, 13 |
tooth | 13 |
touch(ing) | 9, 11, 12, 13 |
trachea | 8 |
transparency | 7, 11 |
trillion | 3, 4, 17 |
trimester | 13, 15 |
trunk | 10 |
U |
|
umbilical cord | 5, 9, 12 |
umbilical vesicle | 6 |
urine | 11 |
uterine tube(s) | 4, 5 |
uterus | 4, 5, 11, 12, 16 |
V |
|
vascular | 11 |
vernix caseosa | 14 |
viability | 14 |
vocal cord development | 12 |
vocal ligaments | 12 |
W |
|
walking | 15 |
water | 12 |
weight | 11, 12, 13, 15 |
white blood cell | 9 |
windpipe | 8 |
woman | 4, 13 |
womb | 4, 14 |
wrinkled | 15 |
wrist | 8 |
Y |
|
yawns | 12 |
yolk sac | 6, 8 |
Z |
|
zygote | 3, 4 |