Placenta & Fetal Membranes 8

In monozygotic twins, what are 3 different fetal and placenta arrangements?

(1)!Embryo splits prior to blastocyst formation, resulting in separate compartments. (2)!Inner cell mass splits, resulting in a shared placenta and chorionic sac. (3)!Gastrula splits, resulting in a shared placenta, chorionic sac, AND amniotic sac.

describe the potential mechanism for pre-eclampsia

Flt-1 (the VEGF receptor we mentioned above) is normally found bound to endothelial cells, and is responsible for blood vessels growth. It may also be found circulating in blood, in the form of sFLt-1 (soluble Flt-1). PLGF, produced by the placenta, binds to Flt-1 to enhance blood vessels growth during pregnancy, especially during the 3rd trimester.. sFlt-1 levels rose significantly, while PLGF levels dropped significantly, as compared to women to did not develop preeclampsia. This suggests that sFlt-1 in the bloodstream "hijacks" PLGF, causing deterioration of existing blood vessels

what is the term for too little and too much amniotic fluid?

Hydramnios/polyhydramnios (excess amniotic fluid). . oligohydramnios too little fluid

If the intestinal endoerm entering the umbilical cord isnt drawn back into the fetal abdomen, what results?

Meckels diverticulum

What siganls extra-embyonic mesodermal cells to differentiate into angiogenic clusters? what receptors determine whether or not a blood cell or endothelial cell is produced?

Oxygen sensitive genes such as HIF-1alpha are turned on to help produce VEGF. Cells expressing Flk1 will differentiate into hemangioblasts which go on to form mature RBCs. Cells that express Flt1 will differentiate into endothelial cells and form the vessel wall.

stromal cells of endometrium undergo decidual reaction after implantation of the embryo, names are given to 3 topographic layers of the deicuda

1. decidua basalis- aossicated with chorion frondosum. form septa that increase surface area for gas/nutrient exchange. SEPTA divide the placenta into compartment called cotyledons! 2. decidual capsularis found on the abembryonic pole, overlying the chorion laeve. 3. decidual parietalis- uterine lining, initially separate from fetus, eventually fuses with chorion laeve and decidual capsularis

what layers separate the chorionic vessels from the maternal blood in the trophoblastic lacunae, thus preventing the mixture of maternal and fetal blood

1. endothelial lining of each capillary 2. extraembryonic mesoderm that didnt form blood vessels 3. cytotrophoblast cells 4. syncytiotrophoblast cells

what are the functions of the amniotic cavity?

1. provides a water cushion to protect embryo from impacts 2. maintains consistent temperature and pressure 3. permits free movement of the fetus 4. acts as a barrier to infection 5. permits symmetrical development of fetus 6. bathes GI tract and lungs with fluid* lack of fluid will affect dev. of these organs

name 3 main functions of the placenta

1. transport of gases,nutrients, wastes, drug metabolites. Maternal antibodies IgG provide passive immunity. 2.acts as barrier between mother & embryonic tissue. >50k-100k daltons wont pass through- excludes most viruses & bacteria. Cancers such as leukemia, lymphoma, and melonomas can cross the placenta. 3. hormone production. hcG maintains corpus luteum, PLGF for angiogenesis, Indoleamine 2,3 deoxygenase- destroys tryptophan on maternal T cells, somatomammotropin- gives fetus priority for glucose

what abnormalities can occur with the umbilical cord?

1. wrap around the babies neck 2. false knots

what week does the amnion form?

2 weeks. e innermost fetal layer.

what is placenta accreta? what is placenta percreta?

Both cause IUGR, plus cotyledon malformation. placenta accreta: chorionic villi adhere to the myometrium. results in total or patrial loss of decidua basalis placenta percreta: chorionic vili penetrate the full thickness of the myometrium

what happens to the amniotic cavity by the end of month 2? what tissues end up fusing? What tissue lines the embryonic cavity?

amniotic is beginning to outgrow the chorionic cavity. with the loss of the chorionic cavity, the amniotic sac, chorion laeve, decidua capsularis*, and decidua parietalis all fuse together. Capsularis eventually degrades, leaving the chorion laeve in contact with the parietalis. Embryo surrounded by chorionic plate. But the amnio (only a few cells thick) is the innermost fetal layer)

what is amniotic banding

amniotic membrane may tear, allowing the legs, arms, fingers, head, or face to become constricted such that part of the structure is outside of the amniotic sac. Amputations or craniofacial deformities may result

what are the two boundaries of the placenta? what branch do the maternal arteries make and what is their role?

chorionic plate and cytotrophoblastic shell. maternal branches make spiral arteries in the decidua that delier oxygenated blood to intervillus space

Describe primary stem villus formation, secondary stem villus formation, and tertiary stem villus

cytotrophoblast grows into the syncytiotrophoblast. these outgrowths form the primary stemm villi. 2.extraembryonic mesoderm, along with the cytotrophoblast, grows into the primary stem villi. no membranes broken. 3. embrynoic blood vessels form in the extraembryonic medsoderm. thus the tertiary stem VILLI contain differentiated BLOOD VESSELS

what is the name for the maternal contribution to the placenta and the fetal contribution?

decidual basalis = moms contribution, chorion frondosium = felal contribution

what tissue is the umbilical cord derived from? what protects the cord from kinking?

extra-embryonic mesoderm, gives rise to the connecting stalk, which eventually forms the umbilical cord. Whartons jelly prevents kinks

describe the development of uteroplacenta circulation

maternal blood vessels anastomose with trophoblastic lacuna in the syncytiotrophoblast. maternal fluid bathes the ebryonic trophoblast and exchanges gases with fetal blood by diffusion. *Maternal and fetal blood dont mix!

when is ammniocentesis performed? what does it check for?

not before 13-14 wks. detect diseases like enzyme in Tay Sachs, determine sex of child, conduct chromosomal analysis to reveal trisomy, NTD with alpha-fetoprotein

how are dizygotic twins formed? one or two placentas?

ovary releases two eggs, each fertilized by a single spern. usually two placents form. however chorions can fuse (shown in B), resulting in erythrocyte mosaicism. In erythrocyte mosaicism, the fetus can be both type A and type O blood (not "type AO") if the mom is type A and the dad is type O.

clinical correlate, what do mal-formed coytyledons on the placenta indicate?

possible damage to the heart valves due to the embryonic heart having to work extra hard, and the newborn's heart may have a murmur. septae ensure adequate of intervillus spaces

what is the chorion frondosum? what is the chorion laeve?

the embryo's functional portion (lots of villi) of the placenta and is located on the embryonic pole. Chorion laeve is located on the abembryonic side of the uterus, where the tertiary villi degenerate.

describe the development of intervillous spaces, what is the outer cytotrophoblast shell and chorionic plate?

the syncytiotrophoblast, cytotrophoblast, and extraembryonic mesoderm penetrate all the wall to the decidua, forming intervilous spaces full of moms blood. layer of cytotrophoblasts that directly abuts deciduea. chorionic plate consists of extraembryonic mesoderm that boarders the chorion