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Details Title: placental anatomy and phyz Description: 4.24.07 Total Flash Cards: 37 Created: 04/29/2007 09:59:00	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term where does the placenta come from? Definition derived from trophectoderm of the blastocyst Term what are the stem cells in the placenta? Definition mononucleated cytotrophoblasts. they can either be: 1. invasive (extravillous) trophoblast (which will penetrate the endometrium and remodel maternal arteries creating a low pressure conduit) 2, villous trophoblast (which will fuse to form a syncytium overlying cytotrophoblasts and a mesenchymal core containing fetal capillaries) Term what is the chorion? Definition The chorion surrounds the embryo and other membranes. It consists of two layers: an outer formed by the primitive ectoderm or trophoblast, and an inner by the somatic mesoderm; with this latter the amnion is in contact. Term how are chorionic villi created? Definition The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo. Chorionic villi are villi that sprout from the chorion, in order to give a maximum area of contact with the maternal blood. Embryonic blood is carried to the villi by the branches of the umbilical arteries, and after circulating through the capillaries of the villi, is returned to the embryo by the umbilical veins. Thus, the villi are part of the border between maternal and fetal blood during pregnancy. Term what is the uterine decidua? Definition Decidua is the term for the uterine lining (endometrium) during a pregnancy. It is formed under the influence of progesterone and serves to support and interact with the gestation. The decidua represents the maternal portion of the placenta. Term what is the fetal circulation designed to do? Definition to accomodate gas exchange in the placenta rather than in the lungs of the fetus Term ductus venosus Definition shunts OXYG blod from UMBILICAL VEIN to IVC Term foramen ovale Definition shunts OXYGEN blood from IVC to left atrium Term ductus arteriosus Definition shunts deoxy blood from right ventricle and pulmonary artery to descending aorta Term chart the path of oxygen from mother to fetus Definition Umbilical arteries carry deoxygenated blood from the fetus to the placenta in the umbilical cord. There are usually two umbilical arteries present together with one umbilical vein in the cord. The maternal vessels--> chorionic villi --> umbilical vein --> ductus venosus --> IVC (avoiding LIVER) right atrium--> Foramen ovale --> (AVOIDING LUNGS) left atrium --> left ventrical -->aorta. Also, if some DEOX blood gets into the right ventricle, goes to the pulmonary arteries --> ductus areteriosus--> aorta --> O2/CO2 exchange. --> umbilical arteries are actually the latter of the internal iliac arteries that supply the hind limbs with blood in the fetus. The umbilical arteries surround the urinary bladder and then carry all the deoxygenated blood out of the fetus through the umbilical cord. Term what are the placental functions? Definition gas xchange, nutrient uptake, waste excretion, horomone metabolism and production, modulation of the maternal immune response, and timing of parturition Term what are trophoblast fuctions? Definition hormone production; nutrient transport; prevents immune rejection, but expressing HLA-G Term what does the trophoblast not express? Definition classical class I and II major histocompatability molecules; HOWEVER, non-classical MHC class i molecule, HLA-G IS EXPRESSED Term where is the primary sight of placental horomone production? Definition the syncytiotrophoblast Term what are Syncytiotrophoblasts? Definition Syncytiotrophoblasts are POLARIZED epithelium, multinucleated cells found in the placenta of human embryos. They are the outer syncytial layer of the trophoblasts and actively invade the uterine wall. They form the outermost fetal component of the placenta (also known as syntrophoblast) and massively increase the surface area available for nutrient exchange between the mother and the fetus. Cells from the syncytiotrophoblast secrete human chorionic gonadotropin. Term what does the syncytiotrophoblasts secrete? (primarliy into maternal circulation) Definition hCG, • hCS, estriol, • progesterone Term what does HCG look like? Definition single alpha-subunit gene - common to LH, FSH and TSH; on chromosome 6; it is a 92 amino acid polypeptide; the BETA subunit is composed of cluster of seven -subunit genes on chromosome 19 145 amino acid polypeptide (24 aa C-terminal extension vs LH-Beta) Term what is the pattern of hCG secretion during pregers? Definition hCG detected in maternal serum 8 days after ovulation. It is involved in implantation and cytotrophoblast product. subunit transcripts restricted to villous syncytiotrophoblast after 6 weeks of pregnancy Term What is the significance of HCG doubling? Definition maternal serum levels initially double every 1.4 days; after the fifth week - levels double every 2.3 days; placental hCG secretion declines to low levels after 10 weeks Term what are hCG actions? Definition maintain the corpus luteum, it acts on the LH/CG receptor to stimulate progesterone synthesis for the activation of adenylyl cyclase and steroidogenesis. The antisera to hCG in early gestation causes pregnancy termination. HCG binds to TSH receptors Term How do you monitor early pregnancy? Definition hCG doubling times; distinguish between intrauterine and ectopic pregnancies (???); use of ultrasound in conjunction with hCG levels Term How do you do prenatal genetic screening? Definition MMS = alpha-fetoprotein, unconjugated estriol, hCG, inhibin A; fetal aneuploidy associated with altered growth of extraembyonic tissues, increased hCG? Term How do you make human chorionic somatomamotrophin? Definition it is produced by syncytiotrophoblasts; maternal serum levels parallel changes in placental mass; [increased levels in multifetal gestations (increased incidence of GDM) peak at 34 weeks, then plateaus] not a useful clinical marker for fetal wellbeing*** Term what are biological activites of hCS? Definition fasting state: increased lipolysis in adipose tissues; fed state: increased glucose uptake by adipose cells, but insulin resistance at other organ sites (liver); NET RESULT: hCS dampens swings in maternal nutrient levels, but hCS most likely affects maternal intermediary metabolism over a long-term nature Term what are biological activites of hCS? ctd. Definition It modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus.. fetal growth hormone - only 3% as potent as hGH; breast epithelial cell proliferation; pregnancies with hCS gene deletions Term where is the primary site of steroidogenesis? Definition syncytiotrophoblast. most of the hormones released enter the maternal circulation Term Lots of horomones are needed. how are some of them produced in such large quantities? KNOW THESE ENZYMES Definition fetal and placental compartments lack enzymes. For example, fetal adrenal: lacks 3Beta-HSD, so the fetus cannot convert DHEA to testosterone and estrogen ; and cannot convert pregnenolone to cortisol. On the other hand, placenta: lacks P450c17 cannot convert pregnenolone to DHEA, therefore, pregnenolone will be coverted to progesterone in large quantities. Term what are the functions of Progesterone? Definition * Progesterone converts the endometrium to its secretory stage to prepare the uterus for implantation. At the same time progesterone affects the vaginal epithelium and cervical mucus. If pregnancy does not occur, progesterone levels will decrease, leading, in the human, to menstruation. Normal menstrual bleeding is progesterone withdrawal bleeding. * During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy. this is done through P's ability to inhibit the production of cytolytic cytokines * Progesterone decreases contractility of the uterine smooth muscle. [2] * In addition progesterone inhibits lactation during pregnancy. The fall in progesterone levels following delivery is one of the triggers for milk production. * A drop in progesterone levels is possibly one step that facilitates the onset of labor. The fetus metabolizes placental progesterone in the production of adrenal mineralo- and glucosteroids. Term where is progesterone made? Definition largely produced by the corpus luteum until about 10 weeks’ gestation. then, placenta emerges as the major source of progesterone after 7-10 weeks Term so given what you know about progesterone (it relaxes smooth muscles), how does RU 486 work? Definition RU 486 = progesterone antagonist--so it causes uterine contractions via: calcium channel biosynthesis and gap junction formation Term where are estrogens made? Definition early pregnancy - androgens derived from maternal bloodstream. by week 20 - the vast majority of maternal urinary estrogens are derived from fetal androgens Term what is primary estrogen precursor? Definition weak androgen (DHEA-sulfate)--produced in large quantities by fetus. the placenta is an incomplete steriodogenic organ. it lacks P450c17 to convert progesterone into androgens, but it is enriched in sulfatase and 3Beta HSD and aromatase. S converts 16 alpha- OH DHEA to 16 - alpha OH DHEA. 3beta HSD and aromatase converts that into estriol. Term What's E1 vs. E2? Definition E1 (estrone) - 1/10th as potent as estradiol; variable levels preclude clinical applications. E2 (estradiol) - equal amounts arise from maternal and fetal DHEAS. E3 (estriol) - 1/100th as potent as estradiol; derived almost exclusively from fetal adrenal; can be used as a test for fetal wellbeing and a marker for fetal aneuploidy. placental production of E1:E2:E3 = 14:5:81 Term what does the thick inner fetal zone of the fetal adrenal corten have? Definition abundant P450c17 activity-- produces large amounts of DHEAS; and minimal 3bHSD activity-- produces very little cortisol Term in the fetal adrenal cortex, what does ACTG stimulate? Definition steroidogenesis. placental 11 BetaHSD deactivates maternal cortisol. ACTH not inhibited by low levels of fetal cortisol anencephalic fetuses - adrenal atrophy after 20 weeks Term what are the actions of estrogens? Definition fetal control of maternal physiology; vasodilation of spiral arteries; parturition: placental CRH; myometrial gap junctions; mammary epithelial cell proliferation Term what else might hCG do? Definition act on uterine endometriun to facilitate a receptive state (decidualization) and on the myometrium to suppress contractile activity