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the placenta


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the development of the placenta has always been of interest to anatomists, researchers, ob, and sonographers. combined studies of EV, hysteroscopy, cvs, an hysterectomy has indicated absence of continuous blood flow in the intervillous spaces before __wk
maternal blood vessels coursing ___ to the placenta circulate blood into the placenta (at basal plate), whereas blood from the fetus reaches this point through the ___
*posterior *umbilical cord
what is the major role of the placenta?
permit the exchange of oxygenated maternal blood with deoxy fetal blood
before birth, the fetal membranes and placenta perform the following 4 functions and activities
protection, nutrition, respiration, and excretion
the fetal portion of the placenta is the ____. the maternal portion is from the ____. the two parts of the trophoblast are __ and __.
*chorion frondosum *decidual basalis *syncitiotrophoblast (outer) and cytotrophoblast (inner)
at birth or ___, the placenta is separated from the fetus and cast from the uterus as the afterbirth
fetal-umbilical circulation originates w/ deoxy blood pumped by the fetal heart through the __ and into the descending AO. the fetal blood continues to circulate into the ____. by term, approx. ___% of the cardiac output is directed through umb. circ.
*ductus arteriosus *umbilical cord *40%
umbilical arteries divide within the placenta into multiple tiny capillary branches that course through the __. the __ arteries of the uterus supply the baby. oxy maternal blood is brought to the placenta through __ to __ branches of spiral arts.
*tertiary villi *spiral *80-100
deoxy blood enters the ___ space near the central part of each placental lobule, where it flows around and over the surface of the villi and exit via a network or __veins
*intervillous spaces *maternal
a very thin layer composed of the capillary wall and trophoblast tissue, normally separates the fetal blood from the maternal blood. this is called the __
placental membrane
the fetal placenta is anchored to the maternal placenta by the ___ and ___. it provides a large area in which materials may be exchanged across the placental membrane and interposed between fetal and maternal circulation
*cytotrophoblastic shell and *anchoring villi
placenta is dedicated to the __ of the fetus. even when exposed to a poor maternal environment, the placenta can often compensate by becoming more ___. eventually, if multiple or severe enough, these stresses can lead to placental damage or fetal demise
*survivial *efficient
composed of capillaries and cytotrophoblast; it is often called a barrier because there are few compounds, endogenous and exogenous, that are unable to cross the placental membranes in detectable amts. blood also doesn't mingle between mother and fetus
placental membrane
the attachment of the cord is usually near the __ of the placenta. if it attaches to the side, it's called ____ normally the placenta implants on the anterior, fundal, and posterior wall of the uterus.
*center *battledore
the chorionic villi are the functional ___ units of the placenta.
a central core with abundant capillaries is surrounded by an inner layer, cytotrophoblast, and an outer layer, syncitiotrophoblast.
chorionic villi
the inner layer of the chorionic villi (cytotrophoblast) produces ___ whereas the outer layer (syncitiotrophoblast) produces protein hormones such as ___, ____, and sex steroids: ___ and ___
*neuropeptides *hCG *human placental lactogen (hPL) *estrogen *progesterone
after the __ week of gestation, most progesterone is produced by the syncitiotrophoblast from maternally derived cholesterol precursors from ovaries.
progesterone production is exclusively a maternal-placental interaction, with no contribution from the ___. the production of placental ___involves an intricate pathway requiring maternal, placental, and fetal contributions
*fetus *estrogen
the function of the hCG is to maintain the __ during pregnancy. it acts like a positive feedback mechanism. it elevates shortly after conception and peaks at 8-10 weeks.
*corpus luteum cyst
the ___ is responsible for the promotion of lipolysis and an anti-insulin action that serves to direct nutrients to the fetus
hPL (human placental lactogen)
the fetal surface of the placenta (portion of the placenta nearest the amniotic cavity) is represented by the echogenic ___ that courses along th eplacental tissue and is found at the junction with the amniotic fluid.
*chorionic plate
in addition to the fetal portion of the placenta, the maternal portion lies at the junction of the __ and the substance of the placenta
maternal blood vessels from the endometrium run behind the basal plate and are often confused with ___. this represents the normal vascularity of this region. it is more apparent when the placenta is located in the ___ or more ___ w/i uterine cavity
*placental abruption/hemmorhage *fundus *posterior
the placenta can be identified as early as __ menstrual weeks with the substance of the placenta assuming a relatively homogeneous echotexture
the substance of the placenta assumes a a relatively homogenous __ appearance during the first part of pregnancy and is easily recognized with its characteristically smooth borders.
thickness of placenta varies with GA w/ min diameter of _to_ mm after 23 wks and rarely exceeds __ mm
*2-3 *50
enlarged placenta is >__mm. thin placenta is <__mm
*50 *2
___ are most often assoc. with Rh sensitization, diabetes or pregnancy, or congenital anomalies. ___ may be associated with IUGR, chromosomal anomalies, severe placenta infarction, diabetes, htn, polyhydramnios, and toxemia (preeclampsia or eclampsia)
*enlarged placenta *thin placenta
after 20wks, intraplacenta _and placental__may begin to appear.cystic structures representing large fetal vessels are commonly observed coursing behind the __and b/w the amnion and chorion layers.placenta is separated from the myometrium by subplacental__
*sonolucencies *calcification *chorionic plate *venous complex
when you look at placental grading you look at the three things. what are the 4 grades?
*chorionic plate, placental substance, and basal layer *0,1,2,3
grade0 appears in all 1st & __ trimester. gr1 appears at __ wks and _% will stay at this gr until term. gr2 can appear at __ wks and __% will stay at this grd until term. gr3 can appear at __wks and rarely seen <_ wks
*second *31 *40% *36 *45 *38 *35
the __ is the specular reflector at the fetal surface of the placenta closest to the amniotic fluid.
chorionic plate
chorionic plate: Grade 0: straight, smooth and ___ Grade 1: subtle ___ (indention) Grade 2: indentions extending into the ___ but not to the basal layer Grade 3: calcified __ reach basal layer often surrounding ___ center
*well defined *undulations *placenta *septa *sonolucent
placental substance: "homogeneously echogenic, no calcifications" is grade __. "pre-pronounced foci and linear, common shaped echogenic densities" is grade ___
*0 *2
placental substance: "few scattered echogenic echoes representing calcifications" is grade ___. "circular densitites with fallout areas in center and large irregular densities that can shadow" is grade ___
*1 *3
basal layer: grade 0: no echogenic ___. grade 1: ___ grade 2: ___arrangement of small echogenic foci grade 3: large and more continuous echogenic areas which can __. have ___
*foci *unchanged *linear *shadow, venous lakes
occasionally the placenta originates in the fundus of the uterus and proceeds along the anterior wall (___) or along the posterior uterune wall (___)
*fundal anterior placenta *fundal posterior placenta
___ should not be confused with placental pathology because placenta outpouches at the time of the contraction so you should wait 15-20 minutes
braxton hicks contractions
the placenta should be scanned longitudinally to see whether it extends into the ___. if it does a TRV scan should be obtained to determine if placenta is located centrally or lies one one side of the cx. placenta can't be diagnosed until >__ weeks
*LUS *20 weeks
there is an apparent change in placenta location during the course of pregnancy in serial scans. as placenta localizes, the cx usually ___ away from the placenta. even if the placenta margin covers the os at 15-17 wks, it is likely to migrate as lus __
*migrates *elongate
the normal trophoblastic invasion of spiral arteries produces a ___ resistance doppler pattern. in the first trimester, the flow velocity waveform shows a nothced appearance in __ which usually disappears with increasing GA and trophoblastic invasion.
*low *notched
the normal term placentahas several characterisitcs at delivery. it measures about __-__ cm in diameter, is discoid in shape, weighs about __g and typically measures less than 4 cm in thickness
*15-20 cm *600 g
occurs when the placenta implants over near to the internal os of the cx. recognized as early as 18-20 weeks.
placenta previa
associated with advanced maternal age, multiparity, uterine anomalies, smoking, prior c-section, or uterine surgery
placenta previa
what is the clinical sign of placenta previa
painless, bright, red vaginal bleeding in the 2nd or 3rd trimester
complications include premature delivery, life-threatening maternal hemorrhage, increased risk of placenta accreta, increased risk of postpartum hemorrhage and IUGR
placenta previa
four types of placenta previa
complete or total previa (covers the os), partial previa(only partially covers the os), marginal previa(doesn't cover the os but its edge comes to the margin of the os), low-lying previa(is implanted in the LUS, its edge does not reach the os but comes w/
placenta previa is considered high risk because of the threat of life-threatening ___ throughout pregnancy. __ and __ scanning show the cx more accurately because of the transducer is closer to the area of interest.
*hemorrhage *TV and TL
___ is the abnormal adherence of part or all the placenta with partial or complete absence of the decidua basalis. chorionic villi grow into the myometrium and the placental villi are anchored to muscle fibers rather than to the intervening decidual cell
placental accreta
the risk of placenta accreta increases in patients with ___
placenta previa
___ is the further extension of the placenta through the myometrium. ___ is the penetration of the uterine serosa and sometimes into the bladder
*placenta increta *placenta percreta
these conditions result from the underdeveloped decidualization of the endometrium. has a high maternal mortality and morbidity rate; risk factors include placenta previa, prior uterine surgeries, leiomyoma, and advanced maternal age
placenta accreta, increta, and percreta
sono: thick heterogeneous placenta with focal outpouching; absent or thin hypoechoic myometrium beneath placenta less than 2mm
placenta accreta, increta, percreta
the presence of one or more accessory lobes connected to the body of the placenta by blood vessels. occurs when the placenta develops a secondarylobe or several other smaller lobes
succenturiate (accessory) lobe
succenturiate lobes have a tendency to develop infarcts and necrosis in __% of deliveries. they may create a placenta previa or be retained in utero after ___. the retention of the succenturiate lobe at delivery may result in postpartum ___ & infection
*50 *delivery *hemorrhage
us appearance: discrete lobe that has placenta texture but is separae from the main body of placenta; with color flow vascular bands are seen connecting the lobes; it may be as large as main lobe of the placenta and appear as two placentas
succenturiate lobe
the entire uterine cavity is lined with the thin placenta;like a belt;rare but serious condition with a fatal outcome for mom and baby;thin membrane occupies the entire periphery of the chorion;covers the GS rather than forming in specific location
placenta membranacea
this condition is diagnosed whent he placental margin is not deformed like normal; interface between the placenta and chorion remains flat; is found in 20% of patients
circummarginate placenta
prematurity has been found as a complication; sono findings are nonspecific as the placental shape is not distorted; usualy no dx sonographically
circummarginate placenta
a placenta with a dense ring around the periphery produced by excessive growth of the surrounding tissue of the 1-2% of pregnancies; is results in placental villi around the border of the placenta that are not covered by chorionic plate
circumvallate placenta
diagnosed when the placental margin is folded, thickened, or elevated with underlying fibrin and hemorrhage; it is associated with PROM, hemorrhage, and placenta abruption
circumvallate placenta
placental abruption is a premature placental detachment and occurs in 1 in ___ pregnancies. bleeding in the ___ occurs with separation. the mortality rate ranges from __to __% and accounts for __to __% of perinatal deaths
*120 *decidua basalis *20-60% *15-25%
clinicallt the pt. may present with any of the following signs: preterm labor, vaginal bleeding, ab pain, fetal distress or demise, and uterine irritability
placental abruption
maternal htn is seen in 50% of ___ and is considered a risk factor. other risk factors for include a previous hx of it, perinatal death, short umbilical cord, premature delivery, fibroids, trauma, placenta previa, cocaine, and other drugs
placenta abruption
two classifications of placenta abruption
retroplacental and marginal
type of placental abruption that results from the rupture of spiral arteries and is a high pressure bleed. it is associated with hypertension and vascular disease. if the blood remains retroplacental, the patient has no visible vaginal bleeding
placental abruption that results from tears of the marginal veins and represents a low pressure bleed. is associated w/ smoking. the hemorrhage dissects beneath the placental membranes and is assoc. w/ little placental detachment
marginal placental abruption
sonographically for placental abruption, the echogenicity depends on the age of the hemorrhage; the acute bleed is __ to __ while the chronic bleed is more ___
*hyperechoic to isoechoic *hypoechoic
___ is a protein derived from fibrinogen, it is found throughout the lacenta, but is more pronounced in the floor of the placenta, the septa, and increases continuously throughout pregnancy
fibrin (deposition)
on the villi and may increase their mechanical stabiliy; the deposits may be the result of eddies in the turbulent flow- the more flow equals increased fibrin deposits; usually seen after 25 weeks and is of no clinical significance
fibrin deposition
sono appearance: it appears as triangular cystic structures beneath the chorionic plate of the placenta or as hypoechoic area beneath the chorionic plate of the placenta; increased vascularity may be seen
fibrin deposition
w/i the intervillous spaces occurs in 1/3 of pregnancies; results from intraplacental hemorrhage caused by breaks in the villous capillaries; inc. with maternal age indicating maturity; sono it appears as sonolucencies seen w/i homogeneous placenta
focal discrete caused by ischemic necrosis; commonly seen in 25% of pregnancies, and is small with no clinical significance; sono it usually isn't identified unless very large in which it appears as a hypoechoic structure; calcs may appear over time
most common tumor of placenta after moles, occuring in 1% of pregs; is considered non-trophoblastic; the tumor is usually small and consists of a benign proliferation of fetal vessels; the majority are capillary in nature that arise beneath the chor.plate
complications include polyhydramnios, hydrops, cardiomegaly, IUGR, and fetal demise, premature labor as a secondary result to polyhydramnios
usually of no clinicial significance but the larger the size the increase the complication; the maternal AFP may be elevated
sono it appears as a circumscribed solid or complex mass that protrudes from the fetal surface of the placenta; prominent high resistant art. signal seen w/i & around tumor; may be located near umb cord site; polyhydramnios and hydrops; up to 5cm
these may become very prominent and should not be confused for a hemorrhage
venouse complex
___ hemorrhage accumulates at site separate from placenta
before 20 wks the uterine artery typically shows high velocity, low resist. pattern particulary for ut. art. on ___ side of placenta

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