Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
42 Cards in this Set
- Front
- Back
|
Placenta |
begins to form in week 2 and fully developed by week 18 fetomaternal origin functions: nutrition, respiration, excretion, endocrine secretion expelled as afterbirth |
|
|
Chorion |
fetal component of placenta |
|
|
Decidua (Endometrium) |
maternal component of placenta |
|
|
Basic Structure of Placenta |
2 plates: chorionic plate (chorion frondosum) and decidual plate (decidua basalis) intervillous space is filled with maternal blood fetal blood vessels are in the chorionic villi placental membrane is the wall of the villus: "barrier" --> separates maternal and fetal blood |
|
|
Cotyledons |
Decidual septa project into the intervillous space but do not reach the chorionic plate divide the placenta into cotyledons term placenta has 15-20 cotyledons |
|
|
Fetal Placental Circulation |
umbilical arteries take poorly oxygenated blood from fetus to placenta chorionic branches go through chorionic plate and enter chorionic villi villi have an extensive arteriocapillary-venous system - brings fetal blood very close to maternal blood, larger surface area for exchange of metabolic products well-oxygenated blood in fetal capillaries drain into veins small veins converge at the umbilical vein umbilical vein provides fetus with oxygen-rich blood |
|
|
Maternal Placental Circulation |
maternal blood enters intervillous space - from spiral endometrial arteries, through gaps in cytotrophoblastic shell, in jet-like fountains propelled by maternal blood pressure blood flows over branch villi - allows exchange of metabolic and gaseous products blood returns through endometrial veins |
|
|
Placental Membrane |
tissue separating maternal and fetal blood 4 layers up to 20 weeks: synctiotrophoblasts, cytotrophoblasts, CT of villus, endothelium of fetal capillaries after 20 weeks: cytotrophoblasts thin out and disappear in most areas, syncytiotrophoblasts are in direct contac w/fetal capillary endothelium most drugs and other substances in maternal plasma enter fetal plasma |
|
|
Placental Endocrine Function |
placental syncytiotrophoblasts produce sever hormones: Human chorionic gonadotropin (hCG) - maintains corpus luteum Human chorionic somatomammotropin (human placental lactogen) - maturation in maternal breast tissue and fetal growth Human Chorionic Thyrotropin - increases metabolic rate Human Chorionic Corticotropin - important for growth Estrogen and progesterone |
|
|
Term Placenta |
discoid shape diameter: 15-20 cm thickness: 2-3 cm weight: 500-600 g fetal side: chorionic plate and umbilical cord maternal side: cotyledons (inspected for completeness after delivery - can cause severe hemorrhage) |
|
|
Structural Placental Abnormalities |
accessory placental lobes bipartite placenta - 2 equal lobes Circumvallate Placenta - extends beyond the chorionic plate |
|
|
Abnormal Placental Implantation Site |
Placenta Previa Placenta Accreta Placenta Increta Placenta Percreta |
|
|
Placenta Previa |
implants in lower uterine segment or cervix can cause bleeding and premature labor |
|
|
Placenta Accreta |
absence of decidua, so placenta adheres to mymetrium may result in severe post-partum bleeding most cases are associated with placenta previa (~60%) many times seen in patients w/C-section scars |
|
|
Placenta Increta |
villi invage the myometrium |
|
|
Placenta Percreta |
villi penetrate full thickness of myometrial wall |
|
|
Amnion |
forms a fluid-filled membranous sac that fills w/amniotic fluid as it enlarges, it obliterates the chorionic cavity forms the epithelial covering of the umbilical cord amniochorionic membrane - fusion of amnion and chorion rupture = "my water broke" |
|
|
Amniotic Fluid |
derived from fetal and maternal sources 99% water eventually acquires desqumated fetal epithelial cells and excretions (meconium and urine) recirculated by fetal swallowing final volume: 700-1000 mL by week 37 |
|
|
Amniotic Fluid Functions |
barrier to infection prevents adhesions cushions and supports fetus controls body temperature |
|
|
Amniotic Bands |
tears in amnion can lead to these can cause fetal damage, even amputation |
|
|
Oligohydramnios |
not enough amniotic fluid may be caused by placental insufficiency, renal agenesis (undeveloped kidneys --> not peeing out fluid), premature rupture of membrane |
|
|
Polyhydramnios |
too much amniotic fluid fetal anomalies (unable to swallow - anecephaly, esophageal atresia) maternal diabetes |
|
|
Premature Rupture of Membranes |
before labor begins most common cause of premature birth fetus is more susceptible to infection |
|
|
Umbilical Cord |
normal dimensions at birth: 50-60 cm in length, 2 cm in diameter |
|
|
Umbilical Cord too long |
nuchal chord - encircles neck of fetus knot formation can occur |
|
|
Umbilical Cord too short |
prevents fetal movement can lead to detachment of placenta |
|
|
Umbilical Cord Vessels |
2 arteries, 1 vein supported by Wharton's Jelly single umbilical artery - may be associated w/other anomalies (1 in 200 newborns) |
|
|
Twins |
~3% of live births Monozygotic/identical Dizygotic/fraternal |
|
|
Monozygotic/Identical |
two embryos result from one zygote time of splitting determines arrangement of fetal membranes (later split = more shared) 3-4/1000 births |
|
|
2 cell Stage Split |
each twin has own placenta, amnion and chorion |
|
|
Blastocyst Stage Split |
most common share placenta and chorionic cavity separate amniontic cavities |
|
|
Bilaminar Disc Stage Split |
share placenta, chorion and amnion (no dividing membrane) least likely to survive conjoined twins |
|
|
Dizygotic/Fraternal Twins |
90% of twins two embryos result from 2 zygotes each twin has own placenta, chorion and amnion chorions and placentas usually fuse ~28/1000 births - increases with maternal age, hereditary, and fertility treatements |
|
|
Twin-twin Transfusion Syndrome |
abnormal sharing of fetal circulation marked disparity of fetal blood volumes death of one or both fetuses may occur all monochorionic twin placentas have vascular anastomoses |
|
|
Molar Pregnancy |
1/1000-2000 pregnancies in US may occur at any age, most common at the extremes (teens and women >40) during 4th/5th month of pregnancy, women may have vaginal bleeding or larger than expected uterus 2 types: complete mole and partial mole |
|
|
Complete Mole |
fertilization of egg that lacks DNA - 90% fertilized by a single sperm that duplicates (46, XX), 10% by 2 separate sperm (46, XX or 46, XY) always diploid all DNA is paternal most removed by curettage may persist or recur - 10% develop into invasive moles, 2.5% develop into choriocarcinomas |
|
|
Complete Mole Gross Findings |
uterine cavity is filled with delicate, cystic structures that resemble a bunch of grapes - swollen chorionic villi no embryo/embryo dies very early on |
|
|
Complete Mole Microscopic Findings |
all or most villi are swollen diffuse trophoblastic hyperplasia no fetal parts/rarely seen |
|
|
Quantitative hCG in Complete Mole |
levels are much higher than in normal pregnancy of similar gestational age serial levels show rapid increase |
|
|
Partial Mole |
fertilization of normal egg either by 2 normal sperm or 1 sperm w/46 chromosomes Karyotype is usually triploid: 69, XXY / 69, XXX / or rarely 69, XYY an embryo develops and may live for several weeks |
|
|
Partial Mole Gross Appearance |
some enlarged villi are present fetal parts can often be seen |
|
|
Partial Mole Microscopic Appearance |
mixed population of villi minimal trophoblastic proliferation |
