بسـم ا الرمحن الرحيـمبسـم ا الرمحن الرحيـم﴾﴾يرفـع اللــه الذين آمنـوا منكــم والذين أوتوا العلــم درجات واللـه مبا تعملون خبرييرفـع اللــه الذين آمنـوا منكــم والذين أوتوا العلــم درجات واللـه مبا تعملون خبري﴿﴿

صـدق ا العظيـمصـدق ا العظيـم))٢٨٢٨اادلـةاادلـة((

جــــامعــة بابــل جــــامعــة بابــل كلیــة ألطــب كلیــة ألطــب

قســـم النسائیــة والتولیــد

نسریــن مالك عبیدد ـ نسائیة وتولید ) دكتوراه(طبیبة اختصاص بورد

زمیلة المجلس العراقي والعربي في طب وجراحة النسائیة والتولید

قســـم النسائیــة والتولیــد

نسریــن مالك عبیدد ـ نسائیة وتولید ) دكتوراه(طبیبة اختصاص بورد

زمیلة المجلس العراقي والعربي في طب وجراحة النسائیة والتولید

Babylon UniversityBabylon UniversityCollege of medicineCollege of medicine

• Department of Obstetrics and Gynaecology

•Dr. Nassrin Malik aubead

•CABOG, FIBMS.OG, DOG, M.B.Ch.B

• Department of Obstetrics and Gynaecology

•Dr. Nassrin Malik aubead

•CABOG, FIBMS.OG, DOG, M.B.Ch.B

Conception, Implantation, and Embryology

Conception: Is the consequence of severalcomplex events that include:1-Final maturation of the spermatozoa, and oocyte.2-Transport of gametes in the female genital tract.3-Fusion of the male, and female gametes.4-The assembly of diploid number of chromosomes.

Conception, Implantation, and Embryology

Conception: Is the consequence of severalcomplex events that include:1-Final maturation of the spermatozoa, and oocyte.2-Transport of gametes in the female genital tract.3-Fusion of the male, and female gametes.4-The assembly of diploid number of chromosomes.

Spermatogenesis :Spermatogenesis :Is production of mature sperm, it occurs in seminiferousIs production of mature sperm, it occurs in seminiferous

tubules of the testis .tubules of the testis .

The primordial germ cells divided to produceThe primordial germ cells divided to producespermatogonia (which located at the basal lamina of tubule),spermatogonia (which located at the basal lamina of tubule),this spermatogonia then divided mitotically at onset ofthis spermatogonia then divided mitotically at onset ofpuberty to produce primary spermatocytes, these undergopuberty to produce primary spermatocytes, these undergofirst meiotic division to produce secondary spermatocytes,first meiotic division to produce secondary spermatocytes,the haploid secondary spermatocytes further divided ( bythe haploid secondary spermatocytes further divided ( bymeiotic division II) to produce the haploid spermatids, thesemeiotic division II) to produce the haploid spermatids, theseround spermatids then differentiated by process calledround spermatids then differentiated by process calledspermiogenesis to motile spermatozoa.spermiogenesis to motile spermatozoa.

Spermatogenesis :Spermatogenesis :Is production of mature sperm, it occurs in seminiferousIs production of mature sperm, it occurs in seminiferous

tubules of the testis .tubules of the testis .

The primordial germ cells divided to produceThe primordial germ cells divided to producespermatogonia (which located at the basal lamina of tubule),spermatogonia (which located at the basal lamina of tubule),this spermatogonia then divided mitotically at onset ofthis spermatogonia then divided mitotically at onset ofpuberty to produce primary spermatocytes, these undergopuberty to produce primary spermatocytes, these undergofirst meiotic division to produce secondary spermatocytes,first meiotic division to produce secondary spermatocytes,the haploid secondary spermatocytes further divided ( bythe haploid secondary spermatocytes further divided ( bymeiotic division II) to produce the haploid spermatids, thesemeiotic division II) to produce the haploid spermatids, theseround spermatids then differentiated by process calledround spermatids then differentiated by process calledspermiogenesis to motile spermatozoa.spermiogenesis to motile spermatozoa.

Round spermatid appear like any othersomatic cells with a distinct nucleus, andduring differentiation a series of changesinclude reduction in size , and formation of atail which allow the sperm cells to swim.

Spermatogonium takes 2 months toproduce 4 mature sperm The mature spermis 60 micrometer long, and mid piece only 5micrometer in diameter.

Spermatozoa produced at onset of pubertyuntil 60 years old of age and beyond.

Round spermatid appear like any othersomatic cells with a distinct nucleus, andduring differentiation a series of changesinclude reduction in size , and formation of atail which allow the sperm cells to swim.

Spermatogonium takes 2 months toproduce 4 mature sperm The mature spermis 60 micrometer long, and mid piece only 5micrometer in diameter.

Spermatozoa produced at onset of pubertyuntil 60 years old of age and beyond.

44+XY

Primordial germ cell enter gonad

Spermatogonium in the tubules

Primory spermatocytesdiploid no. of chromosomes

mitosis

1st meiotic division

22+x

22+x

22+x

22+y

22+y

2nd spermatocytesHaploid no. of chromosomes

2nd meiotic division

spermatide

spermatogenesis

22+y

spermatide

2nd meiotic division

Mature sperm

OOGENESIS:OOGENESIS:The process of oogenesis is different fromThe process of oogenesis is different fromspermatogenesis in a further important ways ;spermatogenesis in a further important ways ;The germ cells in the wall of yolk sac migrate to genitalThe germ cells in the wall of yolk sac migrate to genitalridge. These primordial germ cells differentiated toridge. These primordial germ cells differentiated tooogonia by theoogonia by the1212th weeks in the ovary during intrauterine life, andth weeks in the ovary during intrauterine life, andthen by mitotic division develop into primary oocytesthen by mitotic division develop into primary oocytes( with diploid number of chromosomes) result in a( with diploid number of chromosomes) result in agreate increase in the number of oocytesgreate increase in the number of oocytesUntil these total aboutUntil these total about 77 milion.milion.

OOGENESIS:OOGENESIS:The process of oogenesis is different fromThe process of oogenesis is different fromspermatogenesis in a further important ways ;spermatogenesis in a further important ways ;The germ cells in the wall of yolk sac migrate to genitalThe germ cells in the wall of yolk sac migrate to genitalridge. These primordial germ cells differentiated toridge. These primordial germ cells differentiated tooogonia by theoogonia by the1212th weeks in the ovary during intrauterine life, andth weeks in the ovary during intrauterine life, andthen by mitotic division develop into primary oocytesthen by mitotic division develop into primary oocytes( with diploid number of chromosomes) result in a( with diploid number of chromosomes) result in agreate increase in the number of oocytesgreate increase in the number of oocytesUntil these total aboutUntil these total about 77 milion.milion.

Then primary oocytes undergo the initial phase of theThen primary oocytes undergo the initial phase of thefirst meiotic division before birth, this division isfirst meiotic division before birth, this division isarrested in prophase stage , and is reassumed just priorarrested in prophase stage , and is reassumed just priorto ovulation at puberty to produce secondary oocyteto ovulation at puberty to produce secondary oocyte( with haploid number of chromosomes) and take most( with haploid number of chromosomes) and take mostof cytoplasm ,and first polar body take little cytoplasm.of cytoplasm ,and first polar body take little cytoplasm.The secondary oocyte enters the second meioticThe secondary oocyte enters the second meioticdivision which arrested at metaphase , and is onlydivision which arrested at metaphase , and is onlyreassumed after fertilization to produce a fertilizedreassumed after fertilization to produce a fertilizedovum and second polar body.ovum and second polar body.

The first polar body may also divided into smaller polarThe first polar body may also divided into smaller polarbodies.bodies.

Then primary oocytes undergo the initial phase of theThen primary oocytes undergo the initial phase of thefirst meiotic division before birth, this division isfirst meiotic division before birth, this division isarrested in prophase stage , and is reassumed just priorarrested in prophase stage , and is reassumed just priorto ovulation at puberty to produce secondary oocyteto ovulation at puberty to produce secondary oocyte( with haploid number of chromosomes) and take most( with haploid number of chromosomes) and take mostof cytoplasm ,and first polar body take little cytoplasm.of cytoplasm ,and first polar body take little cytoplasm.The secondary oocyte enters the second meioticThe secondary oocyte enters the second meioticdivision which arrested at metaphase , and is onlydivision which arrested at metaphase , and is onlyreassumed after fertilization to produce a fertilizedreassumed after fertilization to produce a fertilizedovum and second polar body.ovum and second polar body.

The first polar body may also divided into smaller polarThe first polar body may also divided into smaller polarbodies.bodies.

••The mature oocyte isThe mature oocyte is 120120 micrometer inmicrometer indiameter.diameter.One diploid oogonium after mitotic andOne diploid oogonium after mitotic andmeiotic divisions produces one haploidmeiotic divisions produces one haploidmature egg.mature egg.

••The mature oocyte isThe mature oocyte is 120120 micrometer inmicrometer indiameter.diameter.One diploid oogonium after mitotic andOne diploid oogonium after mitotic andmeiotic divisions produces one haploidmeiotic divisions produces one haploidmature egg.mature egg.

44+XX

23

23

Oogonia44XX

Primory oocytePrimory oocyte((diploid no.diploid no. of chromosomesof chromosomes ))

22nd oocyt nd oocytHaploid no. Haploid no.of chromosomes of chromosomes

mitosismitosis

Primordial germ cell in yolk sacPrimordial germ cell in yolk sac

migrate to the ovarymigrate to the ovary

22x

22X

23

22X

22X

23

11stst meiotic ivisionmeiotic ivision

11stst polar bodypolar body

22nd oocyt nd oocytHaploid no. Haploid no.of chromosomes of chromosomes

22ndnd meiotic divisionmeiotic division( after fertilization)( after fertilization)

2nd oocytehaploid no.

of chromosomes

22ndnd polar bodypolar bodyOvum

Trasport of gametes in genetal tractTrasport of gametes in genetal tractand fertilizationand fertilization

Shortly after ovulation the fimbria of the oviduct beginShortly after ovulation the fimbria of the oviduct beginto cover the surfaces of the ovary, and the tube it selfto cover the surfaces of the ovary, and the tube it selfto contract rhythmically.to contract rhythmically.The oocyet surrounded by comulus oophorus is carriedThe oocyet surrounded by comulus oophorus is carriedinto the tube by the sweeping movement of theinto the tube by the sweeping movement of thefimbriae and the motion of the cilia of epithelial lining.fimbriae and the motion of the cilia of epithelial lining.

Shortly after ovulation the fimbria of the oviduct beginShortly after ovulation the fimbria of the oviduct beginto cover the surfaces of the ovary, and the tube it selfto cover the surfaces of the ovary, and the tube it selfto contract rhythmically.to contract rhythmically.The oocyet surrounded by comulus oophorus is carriedThe oocyet surrounded by comulus oophorus is carriedinto the tube by the sweeping movement of theinto the tube by the sweeping movement of thefimbriae and the motion of the cilia of epithelial lining.fimbriae and the motion of the cilia of epithelial lining.

FertilizationFertilizationThe process by which the male and femaleThe process by which the male and femalegametes fused occur in the ampullary regiongametes fused occur in the ampullary regionof the uterine tube. The spermatozoa passof the uterine tube. The spermatozoa passrapidly from the vagina into the uterus andrapidly from the vagina into the uterus andsubsequently into uterine tubes.subsequently into uterine tubes.The spermatozoa upon arrived in the femaleThe spermatozoa upon arrived in the femalegentile tract not fertilizing the oocyte.theygentile tract not fertilizing the oocyte.theymust undergo:must undergo:--

11--Capacitation.Capacitation.

22-- Acrosomal reactionAcrosomal reaction

FertilizationFertilizationThe process by which the male and femaleThe process by which the male and femalegametes fused occur in the ampullary regiongametes fused occur in the ampullary regionof the uterine tube. The spermatozoa passof the uterine tube. The spermatozoa passrapidly from the vagina into the uterus andrapidly from the vagina into the uterus andsubsequently into uterine tubes.subsequently into uterine tubes.The spermatozoa upon arrived in the femaleThe spermatozoa upon arrived in the femalegentile tract not fertilizing the oocyte.theygentile tract not fertilizing the oocyte.theymust undergo:must undergo:--

11--Capacitation.Capacitation.

22-- Acrosomal reactionAcrosomal reaction

Capacitation lasts forCapacitation lasts for 77hours, during this time glycoproteinhours, during this time glycoproteincoat and plasma proteins are removed form the plasmacoat and plasma proteins are removed form the plasmamembrane that overlies acrosomal region of spermatozoa.membrane that overlies acrosomal region of spermatozoa.Completion of capacitaion allows acrosomal reaction toCompletion of capacitaion allows acrosomal reaction tooccur .acrosomal ration occur under influence ofoccur .acrosomal ration occur under influence ofsubstances released from coronasubstances released from corona--radiata cells of the oocyte.radiata cells of the oocyte.Multiple fusion points between plasma membrane and theMultiple fusion points between plasma membrane and theouter acrosomal membrane take place permitting release ofouter acrosomal membrane take place permitting release ofacrosomal content needed to penetrate the corona radiataacrosomal content needed to penetrate the corona radiataand zona pellucida.and zona pellucida.

Capacitation lasts forCapacitation lasts for 77hours, during this time glycoproteinhours, during this time glycoproteincoat and plasma proteins are removed form the plasmacoat and plasma proteins are removed form the plasmamembrane that overlies acrosomal region of spermatozoa.membrane that overlies acrosomal region of spermatozoa.Completion of capacitaion allows acrosomal reaction toCompletion of capacitaion allows acrosomal reaction tooccur .acrosomal ration occur under influence ofoccur .acrosomal ration occur under influence ofsubstances released from coronasubstances released from corona--radiata cells of the oocyte.radiata cells of the oocyte.Multiple fusion points between plasma membrane and theMultiple fusion points between plasma membrane and theouter acrosomal membrane take place permitting release ofouter acrosomal membrane take place permitting release ofacrosomal content needed to penetrate the corona radiataacrosomal content needed to penetrate the corona radiataand zona pellucida.and zona pellucida.

Once the spermatozoa touch zona pellucida itOnce the spermatozoa touch zona pellucida itbecame firmly attack and penetrate rapidlybecame firmly attack and penetrate rapidlyOnce the spermatozoa touch zona pellucida itOnce the spermatozoa touch zona pellucida itbecame firmly attack and penetrate rapidlybecame firmly attack and penetrate rapidly

The permeability of zona pellucida changeThe permeability of zona pellucida changewhen head of the sperm came in contact withwhen head of the sperm came in contact withthe surface of oocyte this result in release ofthe surface of oocyte this result in release ofsubstance that cause alteration in zonasubstance that cause alteration in zonapellocida (zonal reaction)to prevent entry ofpellocida (zonal reaction)to prevent entry ofother sperms .During fusion of the oocyte andother sperms .During fusion of the oocyte andsperm cell membrane( in human ) both headsperm cell membrane( in human ) both headand tail of spermatozoa enter, as soon asand tail of spermatozoa enter, as soon asspermatozoa enter , the egg respond in threespermatozoa enter , the egg respond in threedifferent ways:different ways:

The permeability of zona pellucida changeThe permeability of zona pellucida changewhen head of the sperm came in contact withwhen head of the sperm came in contact withthe surface of oocyte this result in release ofthe surface of oocyte this result in release ofsubstance that cause alteration in zonasubstance that cause alteration in zonapellocida (zonal reaction)to prevent entry ofpellocida (zonal reaction)to prevent entry ofother sperms .During fusion of the oocyte andother sperms .During fusion of the oocyte andsperm cell membrane( in human ) both headsperm cell membrane( in human ) both headand tail of spermatozoa enter, as soon asand tail of spermatozoa enter, as soon asspermatozoa enter , the egg respond in threespermatozoa enter , the egg respond in threedifferent ways:different ways:

11-- The oocyte and zona reactionThe oocyte and zona reactionOocyte membrane become impermeable to otherOocyte membrane become impermeable to otherspermatozoa.spermatozoa.

22-- Resumption ofResumption of 22nd meiotic divisionnd meiotic divisionOocyte finish theOocyte finish the 22nd meiotic division immediately afternd meiotic division immediately afterentry of spermatozoa , it produce theentry of spermatozoa , it produce the 22nd polar body andnd polar body andother daughter cell is definitive oocyte. The definitive oocyteother daughter cell is definitive oocyte. The definitive oocytebecome arrange in a vesicle known as female pronucleus.become arrange in a vesicle known as female pronucleus.33-- The metabolic reaction of the eggThe metabolic reaction of the eggThe nucleus of spermatozoa become swelled and called maleThe nucleus of spermatozoa become swelled and called malepronucleus the male and female pronucleus will come in closepronucleus the male and female pronucleus will come in closecontact and lose their nuclear envelope and fusion of the malecontact and lose their nuclear envelope and fusion of the maleand female pronuclei resulting in a single cell called theand female pronuclei resulting in a single cell called thezygote.zygote.Fertilization completed inFertilization completed in 2020 hours resulting in return tohours resulting in return todiploid genetic materialdiploid genetic material

11-- The oocyte and zona reactionThe oocyte and zona reactionOocyte membrane become impermeable to otherOocyte membrane become impermeable to otherspermatozoa.spermatozoa.

22-- Resumption ofResumption of 22nd meiotic divisionnd meiotic divisionOocyte finish theOocyte finish the 22nd meiotic division immediately afternd meiotic division immediately afterentry of spermatozoa , it produce theentry of spermatozoa , it produce the 22nd polar body andnd polar body andother daughter cell is definitive oocyte. The definitive oocyteother daughter cell is definitive oocyte. The definitive oocytebecome arrange in a vesicle known as female pronucleus.become arrange in a vesicle known as female pronucleus.33-- The metabolic reaction of the eggThe metabolic reaction of the eggThe nucleus of spermatozoa become swelled and called maleThe nucleus of spermatozoa become swelled and called malepronucleus the male and female pronucleus will come in closepronucleus the male and female pronucleus will come in closecontact and lose their nuclear envelope and fusion of the malecontact and lose their nuclear envelope and fusion of the maleand female pronuclei resulting in a single cell called theand female pronuclei resulting in a single cell called thezygote.zygote.Fertilization completed inFertilization completed in 2020 hours resulting in return tohours resulting in return todiploid genetic materialdiploid genetic material

The zygote end by two cell stages. It undergoes a series ofThe zygote end by two cell stages. It undergoes a series ofmitotic division resulting in a rapid increase in the no. of cells,mitotic division resulting in a rapid increase in the no. of cells,the cells are known asthe cells are known as BlastomereBlastomere..AfterAfter 33--44 divisions the zygote become in appearance ofdivisions the zygote become in appearance ofmulberry. It is known asmulberry. It is known as morulamorula ..AtAt 1212--1616 cell stage the morula consist of group of centrallycell stage the morula consist of group of centrallylocated cells. The inner cell mass will give rise to the tissue oflocated cells. The inner cell mass will give rise to the tissue ofembryo Proper , while the outer cells mass forming theembryo Proper , while the outer cells mass forming thetrophoplast which later contribute to the placentatrophoplast which later contribute to the placenta..

The zygote end by two cell stages. It undergoes a series ofThe zygote end by two cell stages. It undergoes a series ofmitotic division resulting in a rapid increase in the no. of cells,mitotic division resulting in a rapid increase in the no. of cells,the cells are known asthe cells are known as BlastomereBlastomere..AfterAfter 33--44 divisions the zygote become in appearance ofdivisions the zygote become in appearance ofmulberry. It is known asmulberry. It is known as morulamorula ..AtAt 1212--1616 cell stage the morula consist of group of centrallycell stage the morula consist of group of centrallylocated cells. The inner cell mass will give rise to the tissue oflocated cells. The inner cell mass will give rise to the tissue ofembryo Proper , while the outer cells mass forming theembryo Proper , while the outer cells mass forming thetrophoplast which later contribute to the placentatrophoplast which later contribute to the placenta..

The morula enter the uterine cavityThe morula enter the uterine cavity 44daysdaysafterafter Fertilization and fluid filled spaceFertilization and fluid filled spacesingle cavity is formed and the embryosingle cavity is formed and the embryoknown asknown as blastocystblastocystThe cells of the inner cell mass whichThe cells of the inner cell mass whichlocated at one pole , and it is from theselocated at one pole , and it is from thesecells that the embryo will form, while thecells that the embryo will form, while theouter cells known as trophoblast whichouter cells known as trophoblast whichflattened to form the epithelial wall offlattened to form the epithelial wall ofblastocyst.blastocyst.

The morula enter the uterine cavityThe morula enter the uterine cavity 44daysdaysafterafter Fertilization and fluid filled spaceFertilization and fluid filled spacesingle cavity is formed and the embryosingle cavity is formed and the embryoknown asknown as blastocystblastocystThe cells of the inner cell mass whichThe cells of the inner cell mass whichlocated at one pole , and it is from theselocated at one pole , and it is from thesecells that the embryo will form, while thecells that the embryo will form, while theouter cells known as trophoblast whichouter cells known as trophoblast whichflattened to form the epithelial wall offlattened to form the epithelial wall ofblastocyst.blastocyst.

ImplantationImplantation

••The trophoblast over embryoblast begin toThe trophoblast over embryoblast begin topenetrate between the epithelial cell ofpenetrate between the epithelial cell ofendometrial tissue of the uterus atendometrial tissue of the uterus at 66th dayth day(penetration and subsequent erosion)(penetration and subsequent erosion)

••The trophoblast over embryoblast begin toThe trophoblast over embryoblast begin topenetrate between the epithelial cell ofpenetrate between the epithelial cell ofendometrial tissue of the uterus atendometrial tissue of the uterus at 66th dayth day(penetration and subsequent erosion)(penetration and subsequent erosion)

The trophoblast produced proteolyticThe trophoblast produced proteolyticenzyme at the time of implantation , theenzyme at the time of implantation , theendometrial tissue is in the secretoryendometrial tissue is in the secretoryphase at this time the uterine glandphase at this time the uterine glandbecome coiled and the endometrium isbecome coiled and the endometrium ishighly odematoushighly odematous

The trophoblast produced proteolyticThe trophoblast produced proteolyticenzyme at the time of implantation , theenzyme at the time of implantation , theendometrial tissue is in the secretoryendometrial tissue is in the secretoryphase at this time the uterine glandphase at this time the uterine glandbecome coiled and the endometrium isbecome coiled and the endometrium ishighly odematoushighly odematous

The blastocyst embeds in the stratum compactumThe blastocyst embeds in the stratum compactumof the decidua, the most frequent site ofof the decidua, the most frequent site ofimplantation being the upper and posterior partimplantation being the upper and posterior partof uterine cavity, it produces a slight projectionof uterine cavity, it produces a slight projectioninto the uterine lumen.into the uterine lumen.According to its relations to the embryoAccording to its relations to the embryo 33 partspartsof the decidua are distinguished:of the decidua are distinguished:--

The blastocyst embeds in the stratum compactumThe blastocyst embeds in the stratum compactumof the decidua, the most frequent site ofof the decidua, the most frequent site ofimplantation being the upper and posterior partimplantation being the upper and posterior partof uterine cavity, it produces a slight projectionof uterine cavity, it produces a slight projectioninto the uterine lumen.into the uterine lumen.According to its relations to the embryoAccording to its relations to the embryo 33 partspartsof the decidua are distinguished:of the decidua are distinguished:--

Decidua basalis:Decidua basalis:--11This lies between the embryo and the muscular wall of theThis lies between the embryo and the muscular wall of theuterus. It bounds the deeper half of implantation cavity anduterus. It bounds the deeper half of implantation cavity andlater on forms the site of attachment of the definitive placenta.later on forms the site of attachment of the definitive placenta.

A number of thinA number of thin--walled sinuses pass through it, bringingwalled sinuses pass through it, bringingblood to the interblood to the inter--villous spaces. It also serves as a barriervillous spaces. It also serves as a barrieragainst the invasion of the muscle by syncytiotrophpblast, andagainst the invasion of the muscle by syncytiotrophpblast, andnormally the chorionic tissue does not penetrate through thenormally the chorionic tissue does not penetrate through the

decidua into the muscledecidua into the muscle..

Decidua basalis:Decidua basalis:--11This lies between the embryo and the muscular wall of theThis lies between the embryo and the muscular wall of theuterus. It bounds the deeper half of implantation cavity anduterus. It bounds the deeper half of implantation cavity andlater on forms the site of attachment of the definitive placenta.later on forms the site of attachment of the definitive placenta.

A number of thinA number of thin--walled sinuses pass through it, bringingwalled sinuses pass through it, bringingblood to the interblood to the inter--villous spaces. It also serves as a barriervillous spaces. It also serves as a barrieragainst the invasion of the muscle by syncytiotrophpblast, andagainst the invasion of the muscle by syncytiotrophpblast, andnormally the chorionic tissue does not penetrate through thenormally the chorionic tissue does not penetrate through the

decidua into the muscledecidua into the muscle..

--::Decidua capsularisDecidua capsularis--22This portion intervenes between the embryo and theThis portion intervenes between the embryo and theuterine cavity and bounds the superficial half of theuterine cavity and bounds the superficial half of theimplantation cavity. As the ovum grows, it bulges intoimplantation cavity. As the ovum grows, it bulges intothe cavity, and by thethe cavity, and by the 1212th week, the growing embryoth week, the growing embryofills the cavity, so that the decidua capsularis becomesfills the cavity, so that the decidua capsularis becomesfused with the deciduafused with the decidua parietalisparietalis

--::Decidua capsularisDecidua capsularis--22This portion intervenes between the embryo and theThis portion intervenes between the embryo and theuterine cavity and bounds the superficial half of theuterine cavity and bounds the superficial half of theimplantation cavity. As the ovum grows, it bulges intoimplantation cavity. As the ovum grows, it bulges intothe cavity, and by thethe cavity, and by the 1212th week, the growing embryoth week, the growing embryofills the cavity, so that the decidua capsularis becomesfills the cavity, so that the decidua capsularis becomesfused with the deciduafused with the decidua parietalisparietalis

--Decidua parietalis:Decidua parietalis:--33This portion is not related to the site ofThis portion is not related to the site ofimplantation and it lines the rest of the cavity ofimplantation and it lines the rest of the cavity ofuterus.uterus.

The decidual spaceThe decidual space ::Is the space bounded by the decidua parietalis and deciduaIs the space bounded by the decidua parietalis and deciduacapsularis.It is obliterated by thecapsularis.It is obliterated by the 1212th week of pregnancy.th week of pregnancy.

The choriodecidual spaceThe choriodecidual space::Is the space between the chorionic villi and the deciduaIs the space between the chorionic villi and the deciduabasalis. It contains maternal blood.basalis. It contains maternal blood.

The decidual spaceThe decidual space ::Is the space bounded by the decidua parietalis and deciduaIs the space bounded by the decidua parietalis and deciduacapsularis.It is obliterated by thecapsularis.It is obliterated by the 1212th week of pregnancy.th week of pregnancy.

The choriodecidual spaceThe choriodecidual space::Is the space between the chorionic villi and the deciduaIs the space between the chorionic villi and the deciduabasalis. It contains maternal blood.basalis. It contains maternal blood.

••Human chorionic gonadotrophin(HCG)Human chorionic gonadotrophin(HCG) isisproduced by the trophoblast.In the first weekproduced by the trophoblast.In the first weekafter implantation , serum hCG levels in theafter implantation , serum hCG levels in themother rise frommother rise from 55 toto 5050 iuiu\\LL..

••By the time the mother has missed her firstBy the time the mother has missed her firstmenstrual period, her hCG levels aremenstrual period, her hCG levels are

••100100 iuiu\\L.L. Commercial testing kits are availableCommercial testing kits are availablethat are sensitive tothat are sensitive to 2525iuiu\\Lin urine.Lin urine.

••A quantitative serum assay showing a level ofA quantitative serum assay showing a level of>> 1515 iuiu\\LL will usually denotewill usually denote

••a pregnancy .With a normal intrauterinea pregnancy .With a normal intrauterinepregnancy , the hCG level doublespregnancy , the hCG level doublesapproximately everyapproximately every 3636--4848 hourshours

••Human chorionic gonadotrophin(HCG)Human chorionic gonadotrophin(HCG) isisproduced by the trophoblast.In the first weekproduced by the trophoblast.In the first weekafter implantation , serum hCG levels in theafter implantation , serum hCG levels in themother rise frommother rise from 55 toto 5050 iuiu\\LL..

••By the time the mother has missed her firstBy the time the mother has missed her firstmenstrual period, her hCG levels aremenstrual period, her hCG levels are

••100100 iuiu\\L.L. Commercial testing kits are availableCommercial testing kits are availablethat are sensitive tothat are sensitive to 2525iuiu\\Lin urine.Lin urine.

••A quantitative serum assay showing a level ofA quantitative serum assay showing a level of>> 1515 iuiu\\LL will usually denotewill usually denote

••a pregnancy .With a normal intrauterinea pregnancy .With a normal intrauterinepregnancy , the hCG level doublespregnancy , the hCG level doublesapproximately everyapproximately every 3636--4848 hourshours

Second week of developmentSecond week of developmentBilaminar germ disk:Bilaminar germ disk:At theAt the 88th day of development, the blastocyst isth day of development, the blastocyst ispartially embedded in endometrial stroma. In areapartially embedded in endometrial stroma. In areaof embryoblast trophoblast differentiated into towof embryoblast trophoblast differentiated into towlayers;inner layer of mononuclatedlayers;inner layer of mononuclated cytotrophoblast,cytotrophoblast,

and outer layerand outer layer of multi nucleated zone without distinctof multi nucleated zone without distinctcell boundaries (syncytiotrophoblast) or calledcell boundaries (syncytiotrophoblast) or called

syncytium.syncytium.

Second week of developmentSecond week of developmentBilaminar germ disk:Bilaminar germ disk:At theAt the 88th day of development, the blastocyst isth day of development, the blastocyst ispartially embedded in endometrial stroma. In areapartially embedded in endometrial stroma. In areaof embryoblast trophoblast differentiated into towof embryoblast trophoblast differentiated into towlayers;inner layer of mononuclatedlayers;inner layer of mononuclated cytotrophoblast,cytotrophoblast,

and outer layerand outer layer of multi nucleated zone without distinctof multi nucleated zone without distinctcell boundaries (syncytiotrophoblast) or calledcell boundaries (syncytiotrophoblast) or called

syncytium.syncytium.

The cells of inner layer differentiated into twoThe cells of inner layer differentiated into twolayerslayersFirst layer of small cuboidal cellsFirst layer of small cuboidal cells(hypoblast)(hypoblast) ,and second layer of high,and second layer of highcolumnar cellscolumnar cells (epiblast),(epiblast), the cells of eachthe cells of eachgerm layer form a flat disk , and togethergerm layer form a flat disk , and togetherknown as bilaminar germ disk , all thisknown as bilaminar germ disk , all thishappen at thehappen at the 88th day of development.th day of development.

The cells of inner layer differentiated into twoThe cells of inner layer differentiated into twolayerslayersFirst layer of small cuboidal cellsFirst layer of small cuboidal cells(hypoblast)(hypoblast) ,and second layer of high,and second layer of highcolumnar cellscolumnar cells (epiblast),(epiblast), the cells of eachthe cells of eachgerm layer form a flat disk , and togethergerm layer form a flat disk , and togetherknown as bilaminar germ disk , all thisknown as bilaminar germ disk , all thishappen at thehappen at the 88th day of development.th day of development.

Embryology:Embryology:In humans following successful fertilization,In humans following successful fertilization,

differentiation of cells into specialized tissues , todifferentiation of cells into specialized tissues , toform interform inter--related organ system , is known as therelated organ system , is known as theembryonic period .It start with the generation ofembryonic period .It start with the generation ofthe embryonic disk during second week postthe embryonic disk during second week postfertilization (fertilization (44 weeks after the last menstrualweeks after the last menstrualperiod), and, conventionally, ends on the last dayperiod), and, conventionally, ends on the last dayof theof the 88th week(th week( 1010 weeks after the last menstrualweeks after the last menstrualperiod); at this point , all organ system formed,period); at this point , all organ system formed,but are not necessarily mature, or functioning.but are not necessarily mature, or functioning.

Embryology:Embryology:In humans following successful fertilization,In humans following successful fertilization,

differentiation of cells into specialized tissues , todifferentiation of cells into specialized tissues , toform interform inter--related organ system , is known as therelated organ system , is known as theembryonic period .It start with the generation ofembryonic period .It start with the generation ofthe embryonic disk during second week postthe embryonic disk during second week postfertilization (fertilization (44 weeks after the last menstrualweeks after the last menstrualperiod), and, conventionally, ends on the last dayperiod), and, conventionally, ends on the last dayof theof the 88th week(th week( 1010 weeks after the last menstrualweeks after the last menstrualperiod); at this point , all organ system formed,period); at this point , all organ system formed,but are not necessarily mature, or functioning.but are not necessarily mature, or functioning.

Third week:Third week:On the dorsal aspect of the bilaminar germ disk, a faintOn the dorsal aspect of the bilaminar germ disk, a faint

groove , the primitive streak, appears on the mid line neargroove , the primitive streak, appears on the mid line nearits caudal end . This is an important event during which aits caudal end . This is an important event during which anumber of developmental landmarks are generated .fornumber of developmental landmarks are generated .forexample, , the primitive streak determines the symmetryexample, , the primitive streak determines the symmetry

and defines the cephalic and caudal poles of the embryo.and defines the cephalic and caudal poles of the embryo.

Third week:Third week:On the dorsal aspect of the bilaminar germ disk, a faintOn the dorsal aspect of the bilaminar germ disk, a faint

groove , the primitive streak, appears on the mid line neargroove , the primitive streak, appears on the mid line nearits caudal end . This is an important event during which aits caudal end . This is an important event during which anumber of developmental landmarks are generated .fornumber of developmental landmarks are generated .forexample, , the primitive streak determines the symmetryexample, , the primitive streak determines the symmetry

and defines the cephalic and caudal poles of the embryo.and defines the cephalic and caudal poles of the embryo.

During the third week ,two other structures become appearanton the embryonic disk: the neural plate and the somites, whichappear as symmetrical eminences on the other side of the midline .Internally, the bilaminar embryo generates the mesodermallayer, ( which is made up of cells which from the primitivenode at the cephalic end of the primitive streak ), migratebetween the ectodermal and endodermal layers .The somitesof paraxial mesodermal cells will appear on day 20 , at a levelcorresponding to the future base of the skull.

During the third week ,two other structures become appearanton the embryonic disk: the neural plate and the somites, whichappear as symmetrical eminences on the other side of the midline .Internally, the bilaminar embryo generates the mesodermallayer, ( which is made up of cells which from the primitivenode at the cephalic end of the primitive streak ), migratebetween the ectodermal and endodermal layers .The somitesof paraxial mesodermal cells will appear on day 20 , at a levelcorresponding to the future base of the skull.

Other structures intimately related to theOther structures intimately related to theembryonic disk develop during this time ; theembryonic disk develop during this time ; theprimary yolk sacprimary yolk sac grows rapidly into thegrows rapidly into theexpanding exocoelomic space .The yolk sac is anexpanding exocoelomic space .The yolk sac is animportant organ exchanging metabolites betweenimportant organ exchanging metabolites betweenthe mother and embryo at the time when there isthe mother and embryo at the time when there isno placenta but there are some chorionic villino placenta but there are some chorionic villiundergo vascularization.undergo vascularization.

Other structures intimately related to theOther structures intimately related to theembryonic disk develop during this time ; theembryonic disk develop during this time ; theprimary yolk sacprimary yolk sac grows rapidly into thegrows rapidly into theexpanding exocoelomic space .The yolk sac is anexpanding exocoelomic space .The yolk sac is animportant organ exchanging metabolites betweenimportant organ exchanging metabolites betweenthe mother and embryo at the time when there isthe mother and embryo at the time when there isno placenta but there are some chorionic villino placenta but there are some chorionic villiundergo vascularization.undergo vascularization.

The live spane of the yolk sac is limited , itThe live spane of the yolk sac is limited , itattains full development by dayattains full development by day 3232 and itsand itscomplex wall start degenerated by the endcomplex wall start degenerated by the endof the sixth week.of the sixth week.

The amniotic memberane is another extraThe amniotic memberane is another extra--embryonic element, which by ayembryonic element, which by ay 1717 isisclosely apposed to the embryonic disk .closely apposed to the embryonic disk .

The live spane of the yolk sac is limited , itThe live spane of the yolk sac is limited , itattains full development by dayattains full development by day 3232 and itsand itscomplex wall start degenerated by the endcomplex wall start degenerated by the endof the sixth week.of the sixth week.

The amniotic memberane is another extraThe amniotic memberane is another extra--embryonic element, which by ayembryonic element, which by ay 1717 isisclosely apposed to the embryonic disk .closely apposed to the embryonic disk .

Fourth week:Fourth week:During this week the embryonic disk folds into anDuring this week the embryonic disk folds into anembryonic cylinder, with in which is acranioembryonic cylinder, with in which is acranio--caudal,caudal,blindblind--ending tube which has three segments ,theending tube which has three segments ,theforegut, the midgut opened to the developing yolk sac,foregut, the midgut opened to the developing yolk sac,and hindgut .this stage marks the start of organogenesisand hindgut .this stage marks the start of organogenesisTheThe 11st organ to become apparent is the primitive heartst organ to become apparent is the primitive heartin the shape of a forwardin the shape of a forward--buckling loop. cardiac activitybuckling loop. cardiac activityis evident by dayis evident by day 2222 post fertilization.post fertilization.

Fourth week:Fourth week:During this week the embryonic disk folds into anDuring this week the embryonic disk folds into anembryonic cylinder, with in which is acranioembryonic cylinder, with in which is acranio--caudal,caudal,blindblind--ending tube which has three segments ,theending tube which has three segments ,theforegut, the midgut opened to the developing yolk sac,foregut, the midgut opened to the developing yolk sac,and hindgut .this stage marks the start of organogenesisand hindgut .this stage marks the start of organogenesisTheThe 11st organ to become apparent is the primitive heartst organ to become apparent is the primitive heartin the shape of a forwardin the shape of a forward--buckling loop. cardiac activitybuckling loop. cardiac activityis evident by dayis evident by day 2222 post fertilization.post fertilization.

••Neurulation ,(the development of nervousNeurulation ,(the development of nervous••system) take place at this stage ofsystem) take place at this stage of

••development,Briefly, the neural plate becomesdevelopment,Briefly, the neural plate becomes••adeep groove on the dorsal aspect of theadeep groove on the dorsal aspect of the

embryo.embryo.

••Neurulation ,(the development of nervousNeurulation ,(the development of nervous••system) take place at this stage ofsystem) take place at this stage of

••development,Briefly, the neural plate becomesdevelopment,Briefly, the neural plate becomes••adeep groove on the dorsal aspect of theadeep groove on the dorsal aspect of the

embryo.embryo.

••it sinks deeper and the opposing crests fuse,it sinks deeper and the opposing crests fuse,generating the neural tube. As closure takegenerating the neural tube. As closure takeplace , the cephalic neuropore closed duringplace , the cephalic neuropore closed duringdayday 2626 and the caudal neuropore at the end ofand the caudal neuropore at the end of44th week . a special population of cellsth week . a special population of cellsdetaches from the lips of the neural crest anddetaches from the lips of the neural crest andmigrates to several specific locations of themigrates to several specific locations of thebody. By the end of thebody. By the end of the 44th week ,the centralth week ,the centralneural system has define segment ,the primaryneural system has define segment ,the primarybrain vesicles, prosencephalon ,brain vesicles, prosencephalon ,mesencephalon and rhombencephalonmesencephalon and rhombencephalon..

••it sinks deeper and the opposing crests fuse,it sinks deeper and the opposing crests fuse,generating the neural tube. As closure takegenerating the neural tube. As closure takeplace , the cephalic neuropore closed duringplace , the cephalic neuropore closed duringdayday 2626 and the caudal neuropore at the end ofand the caudal neuropore at the end of44th week . a special population of cellsth week . a special population of cellsdetaches from the lips of the neural crest anddetaches from the lips of the neural crest andmigrates to several specific locations of themigrates to several specific locations of thebody. By the end of thebody. By the end of the 44th week ,the centralth week ,the centralneural system has define segment ,the primaryneural system has define segment ,the primarybrain vesicles, prosencephalon ,brain vesicles, prosencephalon ,mesencephalon and rhombencephalonmesencephalon and rhombencephalon..

••Toward the end of the fourth week,the foregutToward the end of the fourth week,the foregutseptates along the mid line into the respiratoryseptates along the mid line into the respiratoryand digestive primitive elements ,The ventraland digestive primitive elements ,The ventralpancreatic bud migrate posteriorly to fuse withpancreatic bud migrate posteriorly to fuse withthe dorsal pancreatic buds .the dorsal pancreatic buds .

••The lower respiratory system appears asThe lower respiratory system appears asseptation of the foregut occurs. Two lung budsseptation of the foregut occurs. Two lung budsevident at the end of fourth week.evident at the end of fourth week.

••By dayBy day 2626 , the mesonephric duct and, the mesonephric duct andmesonephros differentiate.Atmesonephros differentiate.At2828 days thedays theureteric buds and the metanephric blastema areureteric buds and the metanephric blastema aredefined structures.defined structures.

••Toward the end of the fourth week,the foregutToward the end of the fourth week,the foregutseptates along the mid line into the respiratoryseptates along the mid line into the respiratoryand digestive primitive elements ,The ventraland digestive primitive elements ,The ventralpancreatic bud migrate posteriorly to fuse withpancreatic bud migrate posteriorly to fuse withthe dorsal pancreatic buds .the dorsal pancreatic buds .

••The lower respiratory system appears asThe lower respiratory system appears asseptation of the foregut occurs. Two lung budsseptation of the foregut occurs. Two lung budsevident at the end of fourth week.evident at the end of fourth week.

••By dayBy day 2626 , the mesonephric duct and, the mesonephric duct andmesonephros differentiate.Atmesonephros differentiate.At2828 days thedays theureteric buds and the metanephric blastema areureteric buds and the metanephric blastema aredefined structures.defined structures.

••Toward the end of the fourth week the body ofToward the end of the fourth week the body ofthe embryo is attached to the yolk sac by athe embryo is attached to the yolk sac by abroad vitelline duct and two vitelline bloodbroad vitelline duct and two vitelline bloodvessels.vessels.

••The yolk sac is placed within the exocoelomicThe yolk sac is placed within the exocoelomicspace.space.

••The vitelline duct and vitelline vessels areThe vitelline duct and vitelline vessels areincluded within umbilical cord just befor theincluded within umbilical cord just befor thecord enters into the amniotic sac.cord enters into the amniotic sac.

••In the cephalic pole of the embryo , fiveIn the cephalic pole of the embryo , fivepharyngeal arches appear in succession.pharyngeal arches appear in succession.Towards the end of the fourth week ,theTowards the end of the fourth week ,thebuccopharyngeal memberane perforates.buccopharyngeal memberane perforates.••

••Toward the end of the fourth week the body ofToward the end of the fourth week the body ofthe embryo is attached to the yolk sac by athe embryo is attached to the yolk sac by abroad vitelline duct and two vitelline bloodbroad vitelline duct and two vitelline bloodvessels.vessels.

••The yolk sac is placed within the exocoelomicThe yolk sac is placed within the exocoelomicspace.space.

••The vitelline duct and vitelline vessels areThe vitelline duct and vitelline vessels areincluded within umbilical cord just befor theincluded within umbilical cord just befor thecord enters into the amniotic sac.cord enters into the amniotic sac.

••In the cephalic pole of the embryo , fiveIn the cephalic pole of the embryo , fivepharyngeal arches appear in succession.pharyngeal arches appear in succession.Towards the end of the fourth week ,theTowards the end of the fourth week ,thebuccopharyngeal memberane perforates.buccopharyngeal memberane perforates.••

••Change in the external appearance:Change in the external appearance:••During the ensuingDuring the ensuing 33 weeks, the outer aspect of theweeks, the outer aspect of the

human embryo changes dramatically,The head startshuman embryo changes dramatically,The head startsto grow faster than the rest of the body and is bentto grow faster than the rest of the body and is bentforward until the end of the seventh week.forward until the end of the seventh week.

••The face is formed by a series of transformations ofThe face is formed by a series of transformations ofthe pharengeal arches.the pharengeal arches.

••Change in the external appearance:Change in the external appearance:••During the ensuingDuring the ensuing 33 weeks, the outer aspect of theweeks, the outer aspect of the

human embryo changes dramatically,The head startshuman embryo changes dramatically,The head startsto grow faster than the rest of the body and is bentto grow faster than the rest of the body and is bentforward until the end of the seventh week.forward until the end of the seventh week.

••The face is formed by a series of transformations ofThe face is formed by a series of transformations ofthe pharengeal arches.the pharengeal arches.

••The eyesThe eyes are in a lateral position and afterare in a lateral position and after 3434ththweek they appear pigmented. As the embryo growsweek they appear pigmented. As the embryo growsbigger ; the eyes appear to migrate towards thebigger ; the eyes appear to migrate towards themedline of the face.medline of the face.

••The eyelidsThe eyelids develop after the sixth week and by thedevelop after the sixth week and by theend of the eighth week the eyes are closed by theend of the eighth week the eyes are closed by theeyelids, which fuse with one another.eyelids, which fuse with one another.

••The eyelids will separate after theThe eyelids will separate after the 2020th week ofth week ofgestation.gestation.

••The earsThe ears differentiate at either side of the neckdifferentiate at either side of the neckearly during the fifth week of gestation and appearearly during the fifth week of gestation and appearto be displaced upwards as the body of embryo gainsto be displaced upwards as the body of embryo gainslength.length.

••The eyesThe eyes are in a lateral position and afterare in a lateral position and after 3434ththweek they appear pigmented. As the embryo growsweek they appear pigmented. As the embryo growsbigger ; the eyes appear to migrate towards thebigger ; the eyes appear to migrate towards themedline of the face.medline of the face.

••The eyelidsThe eyelids develop after the sixth week and by thedevelop after the sixth week and by theend of the eighth week the eyes are closed by theend of the eighth week the eyes are closed by theeyelids, which fuse with one another.eyelids, which fuse with one another.

••The eyelids will separate after theThe eyelids will separate after the 2020th week ofth week ofgestation.gestation.

••The earsThe ears differentiate at either side of the neckdifferentiate at either side of the neckearly during the fifth week of gestation and appearearly during the fifth week of gestation and appearto be displaced upwards as the body of embryo gainsto be displaced upwards as the body of embryo gainslength.length.

••The noseThe nose is present early during the sixth weekis present early during the sixth weekand the nostrils will be plugged with keratinand the nostrils will be plugged with keratinuntil after theuntil after the 2020th week of gestation.Theth week of gestation.Themouth can be recognized after the sixth weekmouth can be recognized after the sixth weekof gestation .However the palate halves willof gestation .However the palate halves willonly fuse during the eighth week .The uvulaonly fuse during the eighth week .The uvularemains bifid for a week or so ,after which itremains bifid for a week or so ,after which itassumes the shape observed later in gestationassumes the shape observed later in gestationor after birth.or after birth.

••The noseThe nose is present early during the sixth weekis present early during the sixth weekand the nostrils will be plugged with keratinand the nostrils will be plugged with keratinuntil after theuntil after the 2020th week of gestation.Theth week of gestation.Themouth can be recognized after the sixth weekmouth can be recognized after the sixth weekof gestation .However the palate halves willof gestation .However the palate halves willonly fuse during the eighth week .The uvulaonly fuse during the eighth week .The uvularemains bifid for a week or so ,after which itremains bifid for a week or so ,after which itassumes the shape observed later in gestationassumes the shape observed later in gestationor after birth.or after birth.

••During the fourth week, the thorax is largelyDuring the fourth week, the thorax is largelyoccupied by the heart.As the growth proceedsoccupied by the heart.As the growth proceedsthe lungs develop within the thorax.the lungs develop within the thorax.

••The upper limb buds appear at aboutThe upper limb buds appear at about 2727th dayth day. The lower limb buds become evident a day. The lower limb buds become evident a daylater.later.

••By the end of the eighth week both the upperBy the end of the eighth week both the upperand lower limbs are fully differentiated, theand lower limbs are fully differentiated, thehead is slightly up right and the embryo has ahead is slightly up right and the embryo has adistinct human appearancedistinct human appearance

••During the fourth week, the thorax is largelyDuring the fourth week, the thorax is largelyoccupied by the heart.As the growth proceedsoccupied by the heart.As the growth proceedsthe lungs develop within the thorax.the lungs develop within the thorax.

••The upper limb buds appear at aboutThe upper limb buds appear at about 2727th dayth day. The lower limb buds become evident a day. The lower limb buds become evident a daylater.later.

••By the end of the eighth week both the upperBy the end of the eighth week both the upperand lower limbs are fully differentiated, theand lower limbs are fully differentiated, thehead is slightly up right and the embryo has ahead is slightly up right and the embryo has adistinct human appearancedistinct human appearance

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