39. Placenta and Fetal Membranes Flashcards
What are the 4 fetal membranes?
Chorion
Amnion
Umbilical vesicle
Allantois
What separates the fetus from the endometrium?
The placenta + 4 fetal membranes
Describe the stem cell ability of the zygote
Totipotent
Expression of cell lineage specific factors begins in the blastocyst:
The ______ becomes the embryo
The _____ becomes the extra-embryonic tissue (i.e., the fetal membranes)
Embryoblast
Trophoblast
What are the 2 parts of the trophoblast layer?
Polar (in direct contact with embryoblast)
Mural (surrounding blastocyst cavity)
In what week of development does blastocyst implantation occur
2nd week
When implantation occurs during the second week of development, the embryoblast becomes the ________, composed of the _______ + _________, the former is what forms the primary germ layers
Bilaminar embryonic disc; epiblast + hypoblast
As implantation takes place, the trophoblast contacts the endometrium, at which time it differentiates into an inner layer called the _____ and an outer layer called the ____ which is what invades and displaces the _____ cells of the endometrium
Cytotrophoblast; syncytiotrophoblast; decidual
The syncytiotrophoblast produces _____, which enters maternal circulation via the _______ network
hCG; lacunar
95-98% of ectopic pregnancies occur in the ____ or _____ of the uterine tube
Ampulla; isthmus
Signs/symptoms of ectopic pregnancy
Abdominal pain
Amenorrhea
Vaginal bleeding
Rupture of oviduct wall
Do ectopic pregnancies produce hCG?
Yes, but at a slower rate than normal pregnancies
The ______ is the thin, tough membrane that surrounds the embryo/fetus and amniotic fluid
Amnion
The amniotic sac forms when amnioblasts separate from the _____ and enclose the developing amniotic cavity; the amnion is then considered continuous with cells of the layer from which it was derived
Epiblast
With development of the amnion, there is development of ______ _____ circulation, supplying O2 and nutritive substances via diffusion through lacunar networks
Primordial uteroplacental
The amnion itself will grow into and eventually obliterate the _____________, as well as form the epithelial covering of the ______
Chorionic cavity; umbilical cord
What is the function of amniotic fluid
Cushions fetus inside uterus, provides space for fetal movement, regulates fetal body temp
[made up of organic proteins, carbs, fats,enzymes, and hormones, as well as inorganic salts, ions, glycophospholipids, steroid hormones]
What is amniotic fluid derived from
Maternal tissue
Interstitial fluid
What are volumes of amniotic fluid like from 10 weeks — 20 weeks — 37 weeks?
10w = 30 mL 20w = 350 mL 37w = 700-1000 mL
[water content changes every 3 hrs, exchange with fetal blood via umbilical cord — ‘dialysis’; fluid secretion from respiratory and GI tracts, as well as fetal urinary system at 11 wks]
Excessive amniotic fluid characterized by abdominal pain, significant swelling/bloating, and breathlessness
Hydramnios
Insufficient amniotic fluid (<400 mL) in which decreased fluid does not provide enough cushion to fetus and umbilical cord — leads to defects in lung dev’t, clubbed extremities, etc.
Oligohydramnios
What causes hydramnios vs. oligohydramnios?
Hydramnios = genetic defect, fetal defect in CNS, or blockage of GI tube
Oligohydramnios = problem with fetal development (renal agenesis, pulmonary hypoplasia), placental abnormality, or maternal HTN
The amnion forms from epiblast. The chorionic sac forms from ___________, which is from __________
Extraembryonic mesoderm; hypoblast
In the formation of the ________, the extraembryonic mesoderm from the hypoblast surrounds the amnion and primary umbilical vesicle (yolk sac), later separating and splitting the mesoderm into 2 layers. These are separated by the __________, a fluid-filled cavity that surrounds the amnion and umbilical vesicle.
Chorionic sac; extraembryonic coelom
