Formation of vessels , intrauterine circulation . Twinning and malformations

1. Formation of vessels, intrauterinecirculation. Twinning and malformations Márk Kozsurek, M.D., Ph.D. mark@kozsurek.hu ED I., 21/11/2017

2. I. Intrauterinecirculation • Nutrients accumulating in the cytoplasm of oocyte will be shared among the blastomeres during segmentation. This can cover the needs until the end of the first week. • Due to implantation blastocyst will have direct access to the maternal nutrients. • Diffusion is sufficient until the end of the second week, later a more effective system is required: circulatory systems develop and heart tube starts beating on 21st-22nd days. Basic concept: development requires energy and nutrients. As the embryo or later the fetus grows, its requirements dramatically increase. More and more complex transport systems have to develop to fullfill the needs.

3. neuraltube heartprimordium extraembryonicmesoderm yolksac blood islands hemangioblasts

4. cavityformationwithinblood islands vasculogenesis: new vessels arise from blood islands angiogenesis: sprouting from existing vessels neuraltube heartprimordium hemangioblasts yolksac angioblasts endothelium hematopoieticstemcells (precursors of allbloodcells)

5. primitive hematopoiesis definitive hematopoiesis primitive hemangioblasts in the splanchnic layer of extraembryonic mesoderm definitive hemangioblasts derived from the AGM (aorta-gonad-mesonephros) area of the intraembryonic mesoderm

6. Vitelline circulation Vitelline circulation: vessels differentiating in the wall of the yolk sac fuse and drain into the caudal end of the heart tube. Periodic contractions of the heart primordium keep blood in motion toward the tissues of the embryo, then vessels reunite and return to the wall of the yolk sac (virtually one closed loop). In the human yolk sac there are very little nutrients stored, so the vitelline circulation might be considered as a „tradition” preserved from evolution (it is essential in reptiles and birds), inspite of this it is very important because the upcoming, more sofisticated circulatory system might be bilt onto this primitive system! Vitelline circulation appears at the beginning of the 3rd week, but by the end of this week it starts to degenerate.

7. Placentalcirculations Umbilical vessels grow through the connecting stalk along the allantois and reach the chorion.

9. term villi Placetal barrier: 1. syncyitiotrophoblast 2. cytotrophoblasts 3. basement membrane of trophoblasts 4. stroma of the villi 5. capillary basement membrane 6. capillary endothelium 1. syncytiotrophoblast 2. - 3. 4. 5. 6. capillary endothelium fused basement membrane of trophoblasts and capillaries

10. II. Twinformation Naturally approx. 1:80, but due to increasing number of IVF where more fertilized eggs are inserted into the uterine cavity the incidence is getting higher and higher.

12. III. Malformations • Geneticaldisorders • Environmentalfactors • Intrauterineinfections • Lack of traceelement, minerals, vitamins • Medicinestakenduringpregnancy • Idiopathic • Amniotic bandconstrictions • Umbilicalcord and placenta abnormalities • Congenitaltumors

13. Down syndrome: trisomy 21 Advancing maternal age. By age 35, a woman's risk of conceiving a child with Down syndrome is about 1 in 350. By age 40, the risk is about 1 in 100, and by age 45, the risk is about 1 in 30. However, most children with Down syndrome are born to women under age 35 because younger women have far more babies. Having had one child with Down syndrome. Typically, a woman who has one child with Down syndrome has about a 1 in 100 chance of having another child with Down syndrome. Being carriers of the genetic translocation for Down syndrome. Both men and women can pass the genetic translocation for Down syndrome on to their children. http://www.mayoclinic.org/

14. Zikavirus and microcephaly

15. NTD (neuraltubedefect)

16. Thalidomide Thalidomide was first marketed in 1957 in West-Germany under the trade-name Contergan. Primarily prescribed as a sedative or hypnotic, thalidomide also claimed to cure insomnia,tension. Afterwards, it was used against nausea and to alleviate morning sickness in pregnant women. Shortly after the drug was sold in West-Germany, between 5,000 and 7,000 infants were born with limb malformations. Only 40% of these children survived. Throughout the world, about 10,000 cases were reported. In November 1961, thalidomide was taken off the market due to massive pressure from the press and public. (wikipaedia.org)

17. Amniotic bandconstrictions It is commonly accepted that amniotic band constrictions occurs when the inner membrane (amnion) ruptures without injury to the outer membrane (chorion). As a result, freely floating fibrous, sticky bands of amnion can entangle the baby reducing blood supply and causing congenital abnormalities. In some cases a complete amputation of digits or limb may occur before birth.

18. Teratoma Usually all the three germ layers are represented in terratomas which mainly develop in the sacrococcygeal region. Skin, hair, sebum, cartilage and bone and also fully developed teeth (!) are frequently seen in them.

19. Umbilicalcordknots False knots are frequent and clinically negligible as might be considered as the local expansions of the Wharton-jelly especially arond those loops formed by umbilical vessels. Real knots may obliterate vessels inside and result in the death of the fetus.

20. Abnormalattachment of placenta

21. IV. Intrauterinediagnosis + Increased nuchal transparency is characteristic for fetuses with Down syndrome. +

22. Amniocentesis 15-17th weeks

23. Chorionicvillussampling 10-12th weeks

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