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| Name = Trophoblast |
| Name = Trophoblast |
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| Latin = trophoblastus; massa cellularis externa |
| Latin = trophoblastus; massa cellularis externa |
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| Image = Blastocyst |
| Image = Diagram of Blastocyst stage.png |
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| Caption = Blastocyst with an [[inner cell mass]] and trophoblast. |
| Caption = [[Blastocyst]] with an [[inner cell mass]] and trophoblast. |
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| System = |
| System = |
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| CarnegieStage = |
| CarnegieStage = |
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| Days = 6 |
| Days = 6 |
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| Precursor = |
| Precursor = |
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| GivesRiseTo = [[ |
| GivesRiseTo = [[Caul]] |
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}} |
}} |
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''' |
The '''trophoblast''' (from [[Greek language|Greek]] {{transliteration|grc|trephein}}: to feed; and {{transliteration|grc|blastos}}: germinator) is the outer layer of cells of the [[blastocyst]]. Trophoblasts are present four days after [[Human fertilization|fertilization]] in humans.<ref>{{cite book |doi=10.1016/b978-0-12-814823-5.00038-6 |chapter=Development of Renin-Angiotensin-Aldosterone and Nitric Oxide System in the Fetus and Neonate |title=Maternal-Fetal and Neonatal Endocrinology |year=2020 |last1=Tang |first1=Jiaqi |last2=Liu |first2=Bailin |last3=Li |first3=Na |last4=Zhang |first4=Mengshu |last5=Li |first5=Xiang |last6=Gao |first6=Qinqin |last7=Zhou |first7=Xiuwen |last8=Sun |first8=Miao |last9=Xu |first9=Zhice |last10=Lu|first10=Xiyuan |pages=643–662 |isbn=978-0-12-814823-5 |s2cid=208378249 }}</ref> They provide nutrients to the [[embryo]] and develop into a large part of the [[placenta]].<ref>{{cite book |doi=10.1016/b978-0-12-801238-3.64664-0 |chapter=Trophoblast |title=Encyclopedia of Reproduction |year=2018 |last1=Soares |first1=Michael J. |last2=Varberg |first2=Kaela M. |pages=417–423 |isbn=978-0-12-815145-7 }}</ref><ref>{{cite journal |last1=Baines |first1=K.J. |last2=Renaud |first2=S.J. |title=Transcription Factors That Regulate Trophoblast Development and Function |journal=Progress in Molecular Biology and Translational Science |date=2017 |volume=145 |pages=39–88 |doi=10.1016/bs.pmbts.2016.12.003 |pmid=28110754 |isbn=978-0-12-809327-6 }}</ref> They form during the first stage of [[pregnancy]] and are the first cells to [[Cellular differentiation|differentiate]] from the [[fertilized]] [[Ovum|egg]] to become extraembryonic structures that do not directly contribute to the embryo. After [[blastulation]], the trophoblast is contiguous with the [[ectoderm]] of the embryo and is referred to as the trophectoderm. <ref name="Douglas VandeVoort Kumar Chang 2009 pp. 228–240">{{cite journal | last1=Douglas | first1=Gordon C. | last2=VandeVoort | first2=Catherine A. | last3=Kumar | first3=Priyadarsini | last4=Chang | first4=Tien-Cheng | last5=Golos | first5=Thaddeus G. | title=Trophoblast Stem Cells: Models for Investigating Trophectoderm Differentiation and Placental Development | journal=Endocrine Reviews | publisher=The Endocrine Society | volume=30 | issue=3 | date=2009-03-18 | issn=0163-769X | doi=10.1210/er.2009-0001 | pages=228–240| pmid=19299251 | pmc=2726840 }}</ref> After the first differentiation, the cells in the human embryo lose their [[Cell potency#Totipotency|totipotency]] because they can no longer form a trophoblast. They become [[Cell potency#Pluripotency|pluripotent]] stem cells. |
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== Structure == |
== Structure == |
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[[File:2907 Embroyonic Disc, Amniotic Cavity, Yolk Sac-02.jpg|thumb|left|Image showing trophoblast differentiated into the two layers of [[cytotrophoblast]] and syncytiotrophoblast during [[Implantation (embryology)|implantation]]]] |
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The trophoblast proliferates and differentiates into two cell layers at approximately six days after fertilization for humans. |
The trophoblast proliferates and differentiates into two cell layers at approximately six days after fertilization for humans. |
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{| class="wikitable" |
{| class="wikitable" |
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!Layer!!Location!!Description |
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|[[Cytotrophoblast]]|| The inner layer || A single-celled inner layer of the trophoblast. |
|[[Cytotrophoblast]]|| The inner layer || A single-celled inner layer of the trophoblast. |
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== Function == |
== Function == |
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Trophoblasts are specialized cells of the [[placenta]] that play an important role in embryo implantation and interaction with the [[decidua]]lized maternal [[uterus]].<ref>{{ |
Trophoblasts are specialized cells of the [[placenta]] that play an important role in embryo [[Implantation (embryology)|implantation]] and interaction with the [[decidua]]lized maternal [[uterus]].<ref>{{cite book |doi=10.1016/bs.pmbts.2016.12.004 |chapter=The Phylogeny of Placental Evolution Through Dynamic Integrations of Retrotransposons |title=Molecular Biology of Placental Development and Disease |series=Progress in Molecular Biology and Translational Science |year=2017 |last1=Imakawa |first1=K. |last2=Nakagawa |first2=S. |volume=145 |pages=89–109 |pmid=28110755 |isbn=978-0-12-809327-6 }}</ref> The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetus’ circulation via the [[umbilical cord]]. This core is surrounded by two layers of trophoblasts, the [[cytotrophoblast]] and the [[syncytiotrophoblast]]. The cytotrophoblast is a layer of mono-nucleated cells that resides underneath the syncytiotrophoblast.<ref name=":0">{{cite web |url=http://www.embryology.ch/anglais/fplacenta/fecond03.html |title=The trophoblast |archive-url=https://web.archive.org/web/20071215103134/http://www.embryology.ch/anglais/fplacenta/fecond03.html |archive-date=15 December 2007 }}</ref> The syncytiotrophoblast is composed of fused cytotrophoblasts which then form a layer that covers the placental surface.<ref name=":0" /> The syncytiotrophoblast is in direct contact with the maternal blood that reaches the placental surface. It then facilitates the exchange of nutrients, wastes and gases between the maternal and fetal systems. |
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In addition, cytotrophoblasts in the tips of villi can differentiate into another type of trophoblast called the extravillous trophoblast. Extravillous trophoblasts grow out from the placenta and penetrate into the decidualized uterus. This process is essential not only for physically attaching the placenta to the mother, but also for altering the vasculature in the uterus. This alteration allows an adequate blood supply to the growing fetus as pregnancy progresses. Some of these trophoblasts even replace the [[endothelial cells]] in the uterine spiral |
In addition, cytotrophoblasts in the tips of villi can differentiate into another type of trophoblast called the [[extravillous trophoblast]]. Extravillous trophoblasts grow out from the placenta and penetrate into the decidualized uterus. This process is essential not only for physically attaching the placenta to the mother, but also for altering the vasculature in the uterus. This alteration allows an adequate blood supply to the growing fetus as pregnancy progresses. Some of these trophoblasts even replace the [[endothelial cells]] in the uterine [[spiral arteries]] as they remodel these vessels into wide bore conduits that are independent of maternal [[vasoconstriction]]. This ensures that the fetus receives a steady supply of blood, and the placenta is not subjected to fluctuations in oxygen that could cause it damage.<ref>{{cite journal |last1=Lunghi |first1=Laura |last2=Ferretti |first2=Maria E |last3=Medici |first3=Silvia |last4=Biondi |first4=Carla |last5=Vesce |first5=Fortunato |title=Control of human trophoblast function |journal=Reproductive Biology and Endocrinology |date=December 2007 |volume=5 |issue=1 |pages=6 |doi=10.1186/1477-7827-5-6 |pmid=17288592 |pmc=1800852 |doi-access=free }}</ref> |
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==Clinical significance== |
==Clinical significance== |
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The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal [[uterus]] is a vital stage in the establishment of [[pregnancy]]. Failure of the trophoblast to invade sufficiently is important in the development of some cases of [[pre-eclampsia]]. Invasion of the trophoblast too deeply may cause conditions such as [[placenta accreta]], [[placenta increta]], or [[placenta percreta]]. |
The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal [[uterus]] is a vital stage in the establishment of [[pregnancy]]. Failure of the trophoblast to invade sufficiently is important in the development of some cases of [[pre-eclampsia]]. Invasion of the trophoblast too deeply may cause conditions such as [[placenta accreta]], [[placenta increta]], or [[placenta percreta]]. |
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[[Gestational trophoblastic disease]] is a pregnancy-associated concept, forming from the villous and extravillous trophoblast cells in the placenta.<ref name=" |
[[Gestational trophoblastic disease]] is a pregnancy-associated concept, forming from the villous and extravillous trophoblast cells in the placenta.<ref name="Ning Hou Morse Lash 2019">{{cite journal |last1=Ning |first1=Fen |last2=Hou |first2=Houmei |last3=Morse |first3=Abraham N. |last4=Lash |first4=Gendie E. |title=Understanding and management of gestational trophoblastic disease |journal=F1000Research |date=10 April 2019 |volume=8 |pages=428 |doi=10.12688/f1000research.14953.1 |pmid=31001418 |pmc=6464061 |doi-access=free }}</ref> |
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[[Choriocarcinoma]] are trophoblastic tumors that form in the uterus from villous cells.<ref name=" |
[[Choriocarcinoma]] are trophoblastic tumors that form in the uterus from villous cells.<ref name="Ning Hou Morse Lash 2019"/> |
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Trophoblast stem cells (TSCs) are cells that can regenerate and they are similar to [[embryonic stem cell]]s (ESCs) in the fact that they come from early on in the trophoblast lifetime.<ref name=" |
Trophoblast stem cells (TSCs) are cells that can regenerate and they are similar to [[embryonic stem cell]]s (ESCs) in the fact that they come from early on in the trophoblast lifetime.<ref name="Latos Hemberger 2014">{{cite journal |last1=Latos |first1=P.A. |last2=Hemberger |first2=M. |title=Review: The transcriptional and signalling networks of mouse trophoblast stem cells |journal=Placenta |date=February 2014 |volume=35 |pages=S81–S85 |doi=10.1016/j.placenta.2013.10.013 |pmid=24220516 }}</ref> In the [[placenta]], these stem cells are able to differentiate into any trophoblast cell because they are pluripotent.<ref name="Latos Hemberger 2014"/> |
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==Additional images== |
==Additional images== |
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File:Gray39.png|Scheme of placental circulation. |
File:Gray39.png|Scheme of placental circulation. |
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File:HumanEmbryogenesis.svg|The initial stages of [[human embryogenesis]] |
File:HumanEmbryogenesis.svg|The initial stages of [[human embryogenesis]] |
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File:Histopathology of tubal pregnancy.jpg|Histopathology of a [[Chorionic villi|chorionic villus]], in a [[tubal pregnancy]], with labeled cytotrophoblasts and syncytiotrophoblasts. |
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</gallery> |
</gallery> |
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* {{EmbryologySwiss|iperiodembry/carnegie02}} |
* {{EmbryologySwiss|iperiodembry/carnegie02}} |
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{{Embryology}} |
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{{Extraembryonic and fetal membranes}} |
{{Extraembryonic and fetal membranes}} |
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{{Authority control}} |
{{Authority control}} |
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| Trophoblast | |
|---|---|
Blastocyst with an inner cell mass and trophoblast.
| |
| Details | |
| Days | 6 |
| Gives rise to | Caul |
| Identifiers | |
| Latin | trophoblastus; massa cellularis externa |
| MeSH | D014327 |
| TE | E6.0.1.1.2.0.2 |
| FMA | 83029 |
| Anatomical terminology | |
The trophoblast (from Greek trephein: to feed; and blastos: germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans.[1] They provide nutrients to the embryo and develop into a large part of the placenta.[2][3] They form during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg to become extraembryonic structures that do not directly contribute to the embryo. After blastulation, the trophoblast is contiguous with the ectoderm of the embryo and is referred to as the trophectoderm. [4] After the first differentiation, the cells in the human embryo lose their totipotency because they can no longer form a trophoblast. They become pluripotent stem cells.
The trophoblast proliferates and differentiates into two cell layers at approximately six days after fertilization for humans.
| Layer | Location | Description |
|---|---|---|
| Cytotrophoblast | The inner layer | A single-celled inner layer of the trophoblast. |
| Syncytiotrophoblast | The outer layer | A thick layer that lacks cell boundaries and grows into the endometrial stroma. It secretes hCG in order to maintain progesterone secretion and sustain a pregnancy. |
| Intermediate trophoblast (IT) | The implantation site, chorion, villi (dependent on subtype) | An anchor placenta (implantation site IT). |
Trophoblasts are specialized cells of the placenta that play an important role in embryo implantation and interaction with the decidualized maternal uterus.[5] The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetus’ circulation via the umbilical cord. This core is surrounded by two layers of trophoblasts, the cytotrophoblast and the syncytiotrophoblast. The cytotrophoblast is a layer of mono-nucleated cells that resides underneath the syncytiotrophoblast.[6] The syncytiotrophoblast is composed of fused cytotrophoblasts which then form a layer that covers the placental surface.[6] The syncytiotrophoblast is in direct contact with the maternal blood that reaches the placental surface. It then facilitates the exchange of nutrients, wastes and gases between the maternal and fetal systems.
In addition, cytotrophoblasts in the tips of villi can differentiate into another type of trophoblast called the extravillous trophoblast. Extravillous trophoblasts grow out from the placenta and penetrate into the decidualized uterus. This process is essential not only for physically attaching the placenta to the mother, but also for altering the vasculature in the uterus. This alteration allows an adequate blood supply to the growing fetus as pregnancy progresses. Some of these trophoblasts even replace the endothelial cells in the uterine spiral arteries as they remodel these vessels into wide bore conduits that are independent of maternal vasoconstriction. This ensures that the fetus receives a steady supply of blood, and the placenta is not subjected to fluctuations in oxygen that could cause it damage.[7]
The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal uterus is a vital stage in the establishment of pregnancy. Failure of the trophoblast to invade sufficiently is important in the development of some cases of pre-eclampsia. Invasion of the trophoblast too deeply may cause conditions such as placenta accreta, placenta increta, or placenta percreta.
Gestational trophoblastic disease is a pregnancy-associated concept, forming from the villous and extravillous trophoblast cells in the placenta.[8]
Choriocarcinoma are trophoblastic tumors that form in the uterus from villous cells.[8]
Trophoblast stem cells (TSCs) are cells that can regenerate and they are similar to embryonic stem cells (ESCs) in the fact that they come from early on in the trophoblast lifetime.[9] In the placenta, these stem cells are able to differentiate into any trophoblast cell because they are pluripotent.[9]
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Human embryonic development in the first three weeks
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| Week 2 (Bilaminar) |
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| Week 3 (Trilaminar) |
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