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88 Cards in this Set
- Front
- Back
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what is a zygote?
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a fertilized egg
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what are the immediate stages of development of the zygote
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cleavage of cells up to stage 32 cells at which it is called a morula
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what is a morula
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a zygote which has divided to around 32 cells and resembles a mulberry
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what process does a morula undergo
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compaction
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what is compaction? what 2 molecules are important in this?
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maximising of intracellular contact
formation of junctions between outer layers of cells B catenin and E cadherin are important occurs in the trophoblast cells (trophoectoderm) |
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what does the trophoectoderm of the blastocyte contain?
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compacted trophoblast cells
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what are the important stages of the development of the blastocyst
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1) assymetrical division: division of cells into trophoectoderm and inner cell mass
2) adhesion of trophoectoderm (compaction) 3) formation of blastoceol cavity |
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what role does the zona pellucida play in formation of the blastocyte
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prevents the embryo falling apart during cleavage
also prevents formation of chimeric conceptus: 2 dizygotic twins merged |
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what is a chimeric conceptus and what prevents its formation
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2 dizygotic twins merged
zona pellucida prevents it |
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what is the extraembryonic part of the blastocyte?
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the trophoectoderm
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what is a zygote?
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a fertilized egg
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|
|
what are the immediate stages of development of the zygote
|
cleavage of cells up to stage 32 cells at which it is called a morula
|
|
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what is a morula
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a zygote which has divided to around 32 cells and resembles a mulberry
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what process does a morula undergo
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compaction
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what is compaction? what 2 molecules are important in this?
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maximising of intracellular contact
formation of junctions between outer layers of cells B catenin and E cadherin are important occurs in the trophoblast cells (trophoectoderm) |
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what does the trophoectoderm of the blastocyte contain?
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compacted trophoblast cells
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what are the important stages of the development of the blastocyst
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1) assymetrical division: division of cells into trophoectoderm and inner cell mass
2) adhesion of trophoectoderm (compaction) 3) formation of blastoceol cavity |
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what role does the zona pellucida play in formation of the blastocyte
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prevents the embryo falling apart during cleavage
also prevents formation of chimeric conceptus: 2 dizygotic twins merged |
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what is a chimeric conceptus and what prevents its formation
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2 dizygotic twins merged
zona pellucida prevents it |
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what is the extraembryonic part of the blastocyte?
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the trophoectoderm
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what does the formation of junctions in the trophoectoderm achieve?
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polarity of the cells, transformation from radically symmetrical to highly polarised
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what are the two main effects/ outcomes of maternal recognition of pregnancy?
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1) change in reproductive pattern from cyclic to non cyclic
2) further decidualization of the endometrium |
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what hormone ensures maternal recognition of pregnancy and how?
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HCG secreted by trophoblast cells act on luteal cells of corpus luteum in ovary (act on LH receptors)
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what receptors does HCG act on in the corpus luteum?
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LH receptors
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what is the result of LH receptor stimulation in corpus luteum?
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prevention of luteolysis
prolongs life of corpus luteum |
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what hormone levels are found as a result of maternal recognition of pregnancy?
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high progesterone levels
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what are the consequences of high progesterone levels in maternal recognition of pregnancy?
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prevents ovulation
prolongs luteal phase of endometrium encourages decidualisation of endometrium |
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what occurs in the stromal reaction? 5 things
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1) thinning of mucus
2) loss of glycocalyx, a charged side chain 3) flattening of microvilli 4) angiogenesis, increased permeability and oedema 5) lose -ve charge to epithelium |
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what happens when the blastocyte attaches in terms of the stromal reaction?
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attachment encourages further decidualisation of the whole endometrium
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what is the part of the decidua overlying the conceptus?
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the decidua capsularis
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what is the part of the decidua underlying conceptus?
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decidua basalis
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what is the decidua parietalis
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the part of decidua not in contact with conceptus
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briefly, what are the 4 methods of language of attachment?
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endometrium
- LIF - HBEGF like growth factor - MUC1 blastocyte: - HSPG |
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how does the endometrium use LIf in attachment?
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LIF produced by endometrium glands
receptors develop on epithelium and stroma global reaction, needs presence of oestrogen encourages receptivity and further decidualisation |
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what is the role of HB EFG -liek growth factor in attachment?
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in presence of blastocyte
requires eostrogen endometrium produces Heparin binding EFG like growth factor reacts with receptors on blastocyte causes breakdown / proteolysis of zona pellucida and attachment of embryo |
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how does the presence of the blastocyte allow the endometrium to talk to it?
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may give a signal to endometrium to allow production og HBEFG liek growth factor
or may make endometrium receptive to a signal which is already present. |
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how does HBEFG like growth factor react with the blastocyte?
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blastocyte has 2 receptors for it
heparin sulphate EFG receptorss causes proteolysis of zona pellucida and attachment of blastocyte |
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what is zipper theory?
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trophoblast of blastocyte produces Heparin sulphate proteoglycans HSPG
react with receptors on endometrium to allow attachment |
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what kind of signal is MUC1?
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"go away"
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what happens to MUC1 signal during attachment?
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it is downregulated
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what part of the blastocyte helps with invasion and what does it do?
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trophoblast: develops syncytiotrophoblast and cytotrophoblast
syncytiotrophoblast; finger like prjections isolate and digest stromal / epithelial cells breaks through basement membrane |
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what is the role of cytotrophoblasts?
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proliferation of new trophoblast
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what is "interstitial implantation"
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occurs in humans
embryo grows in wall of uterus, not in cavity obliterates cavity as it grows |
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what happens to the uterine tissue as a result of invasion?
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destroys glandular tissue
releases primary metabolic substrates "yolk" equivalent |
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what type of nutrition is facilitated by invasion?
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histotrophic nutrition form metabolic substances released from uterine tissue
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what happens to invasion in an eptopic pregnancy, and why?
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becomes more invasive / dangerous
either 1) inadequate restriction by mother 2) blastocyte trying to overcome inadequate nutrition at ectopic site |
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what are the main "words" in the language of invasion?
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endometrium;
1) TGF B 2) VGF, proliferin 3) TGF, PDGF, PGF trophoblast: 1) proteolytic enzymes eg MMP |
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what is MMP and what is its role in invasion
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Matrix metalloprotein, produced by trophoblast, especially from finger like projections, essential to break through Basement membrane
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what is TGF B and what is its role in invasion
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transforming growth factor B, it restricts activity of finger like projections of trophoblast.
it also takes part in encouraging angiogenesis |
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what factors encourage angiogenesis?
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PFGF, (platelet derived growth factor) PGF (placental growth factor) VEGF (vascular endothelial growth factor), proliferin, TGF
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what part of the blastocyte helps with invasion and what does it do?
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trophoblast: develops syncytiotrophoblast and cytotrophoblast
syncytiotrophoblast; finger like prjections isolate and digest stromal / epithelial cells breaks through basement membrane |
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what is the role of cytotrophoblasts?
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proliferation of new trophoblast
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what is "interstitial implantation"
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occurs in humans
embryo grows in wall of uterus, not in cavity obliterates cavity as it grows |
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what happens to the uterine tissue as a result of invasion?
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destroys glandular tissue
releases primary metabolic substrates "yolk" equivalent |
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what type of nutrition is facilitated by invasion?
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histotrophic nutrition form metabolic substances released from uterine tissue
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what happens to invasion in an eptopic pregnancy, and why?
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becomes more invasive / dangerous
either 1) inadequate restriction by mother 2) blastocyte trying to overcome inadequate nutrition at ectopic site |
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what are the main "words" in the language of invasion?
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endometrium;
1) TGF B 2) VGF, proliferin 3) TGF, PDGF, PGF trophoblast: 1) proteolytic enzymes eg MMP |
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what is MMP and what is its role in invasion
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Matrix metalloprotein, produced by trophoblast, especially from finger like projections, essential to break through Basement membrane
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what is TGF B and what is its role in invasion
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transforming growth factor B, it restricts activity of finger like projections of trophoblast.
it also takes part in encouraging angiogenesis |
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what factors encourage angiogenesis?
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PFGF, (platelet derived growth factor) PGF (placental growth factor) VEGF (vascular endothelial growth factor), proliferin, TGF
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which factor is reduced in preeclampsia and what is the result of this?
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VEGF may be reduced, may cause low birth weight
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what are the main steps (briefly) in establishment of maternal circulation
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1)cytotrophoblast form anchoring villi
2) lacunar network forms 3) unplugging and remodelling of spiral arteries |
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what is an anchoring villi and when does it form?
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column of cytotrophoblast cells which invades the uterine stroma, forms as maternal circualation is becoming established
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what are lacunae?
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lakes formed in the syncytiotrophoblast as a result of digested material from uterine wall
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explain how the lacunar network contributes to establishing maternal circulaion
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lacunar network reaches spiral artery ends so that blood from the arteries can spurt into the lacunae. villi then sit in the lacunae, bathed in maternal blood
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what week sees the unplugging of maternal arteries?
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12th week
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which type of cytotrophoblast sees the remodelling of spiral arteries?
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extravillous CTs
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describe in detail the remodelling of spiral arteries
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- replace smooth muscle and endotherlium
- form a hybrid vessel - EVCTs released from end of anchoring villi - increase diameter and reduce resistance of vessels - ensures maximisation of maternal blood flow - EVCTs undergo epithelial - endothelial transition |
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which trimester has low oxygen levels? why?
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first trimester because spiral arteries not unplugged
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what molecular signal is important in allowing invasion of trophoblasts into the uterine stroma
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integrin switch
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which integrins are switched on usually? what is the name of this receptor?
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a6b4 - basal lamina receptor
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which integrins are switched on for invasion? i.e. hiking boots...
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a5b1 avb1 a1b1
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what goes wrong with integrin switch in preeclampsia?
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a1b1 may not be expressed, resulting in shallower implantation and insufficient remodelling of spiral arteries
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what is the choriovittelline placenta, and when is it important?
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transient placenta formed from yolk sac endoderm and chorionic mesoderm
occurs during the histotrophic phase of nutrition |
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in histotrophic phase of nutrition, how are nutrients delivered to embryo?
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arteries develop in the embryonic and extraembryonic mesoderm which deliver nutrients - fetal heart pumps blood around embryo.
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what is the chorioalantoic placenta?
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develops when alantois (endoderm and mesoderm) fuses with chorion. this is the proper placenta.
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what occurs in the 1st trimester in terms of change to haemotrophic nutrition
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1) maternal circulation develops
2) fetal circulation develops and establishes itself 3) chorionic villi develop |
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what occurs in the second trimester and third trimester?? in terms of haemotrophic nutrition changeover
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growth and remodelling of villi an fetoplacental capillaries for more efficient transport
haemotrophic support from extraembryonic mesoderms |
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what is placenta praevia
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occurs when implantation occurs near to the cervical os. causes bleeding in second stage of pregnancy
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what is the sequence of arteries in the uterus from myometrium to endometrium?
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uterine and ovarian arteries
form arcuate artery from this comes straight radial arteries headed for centre these form spiral arteries in the endometrium |
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what is the extent of development of fetal circulation in the first trimesters?
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formation of primary, secondary and tertiary villi
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describe a primary villus
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column, cytotrophoblast covered by syncytium
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describe a secondary villus?
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mesoderm invades primary villus
still has a column of cytotrophoblasts at top, extending towards endometrium |
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describe a tertiary villous
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haematopoetic cells in mesoderm have developed into a primitive capillary network. this joins up with the umbilical arteries to form the fetal circulation
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at what week has the tertiary villous formed?
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2-4 weeks
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which comes first, fetal or maternal circulation?
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fetal
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what is the chorion frondosum
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the part of the chorion which is at the embryonic pole. develops villi
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what is the chorion laeve
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the part of the chorion not at embryonic pole. villi are small and regress. no exchange takes place here.
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