Placenta and fetal membranes Flashcards
what are all the fetal membranes?
Chorion
amnion
umbilical vesicle
allantois
What is the function of the Placenta? and what are its two components
the Placenta is a fetomaternal organ whith two components
- fetal part = chorionic sac (outermost fetal membrane)
- Maternal part = derived from endometrium
Exchange of nutrients and O2 occurs between the maternal and fetal blood streams via the placenta
Vessels in the umbilical cord connect the placental circulation with the fetal circulation
what are the extraembryonic structures?
Amnion
umbilical vesicle
connecting stalk
chorionic sac
what are the three layers of the decidua? and what is it?
Functional layer of the endometrium that separates from the remainder of the uterus after parturition
-pale staining cells with glycogen and lipid accumulation
Decidua basalis: deep to the conceptus. forms that maternal part of the placenta
Decidua capsularis: superficial and overlies the conceptus
Decidua parietalis: remaining parts of the decidua
8 step summary of implantation
1) implantation of the blastocyst in the uterine endometrium begins at the end of the 1st week, completed by the end of the 2nd week
2) Zona pellucida degenerates at day 5 due to enlarging of the blastocyst and enzymatic lysis
3) Blastocyst adheres to the endometrial epithelium (day 6)
4) trophoblast differentiates into two layers, the syncytiotrophoblast and the cytotrophoblast (day 7)
- syncytiotrophoblast erodes endometrial tissues and blastocytes begins to embed in the endometrium day 8
5) Blood filled lacunae appear in the syncytiotrophoblast at day 9
6) Lacunar networks form by fusion of adjcent lacunae at days 10 and 11
7) Syncytiotrophoblasts erodes endometrial blood vessels allowing maternal blood to seep in and out of lacunar networks and establishing uteroplacental circulation at days 11 and 12
8) Primary chorionic villi develop at days 13 and 14
What is an ectopic pregnancy and what are some signs?
Implantation of blastocyte outside the uterine cavity
-most occur in the oviduct in the ampulla or the isthmus
signs:
- abdominal pain
- amenorrhea
- vaginal bleeding
- rupture of the oviduct wall
- affected tube/conceptus usually surgically removed
what is the chorionic sac? and how does the extraembryonic, somatic, splanchnic and coelom mesoderm interact with the chorionic sac?
Chorionic sac is the extraembryonic somatic mesoderm plus the cytotrophoblasts and the syncytiotrophoblasts
Extraembryonic mesoderm (from hypoblast) surrounds the amnion and primary umbilical vessivel
Extramembryonic somatic mesoderm lines the trophoblast and covers the amnion
extraembryonicsplanchnic mesoderm surrounds the umbilical vesicle
extraembryonic coelom is the fluid fillded cavity that surrounds the amnion and umbilical vesicle
What is the amnion?
Amnion (amnionic sac) is a thin though membrane that surrounds the embryo and fetus that is filled with amniotic fluid
amnioblasts separate from the epiblast and then eclose the developing amniotic cavity
what is amniotic fluid and its main functions?
Initially derived from maternal tissue and intersitial fluid
- fetal urinary system will excrete amniotic fluid
- Respiratory system and GI will also excrete
- done via a dialysis likeexchange via umbilical cord
Functions to cushion the fetus and permits fetal movements and regulat the fetus body temperature
- organic compounds (proteins, carbs, fats, enzymes, hormones)
- inorganic salts, ions, glycophospholipids, and steriod hormones
Hydramnios?
Excessive amniotic fluid
Genetic defect, a fetal defect in the central nervous system or blockage of the gastrointestinal tube
Clinical signs include abdominal pain or bloating and breathlessness
oligohydramnios?
insufficient amniotic fluid that is less than 400 mL
Problem with the fetal development due to renal agenesis or pulmonary hypoplasia
Placental abnormality or maternal High blood pressure
Decreased fluid does not provide enough cushion to fetus and umbilical cord
formation of the amnion/chorionic sac
Decidua capularis forms capsule covering surface of the chorionic sac
Embryo will enlarge causing the decidua capularis to bulge into the uterine cavity where it thins and fuses with the decidua parietalis on the opposite wall and obliterates the uterine cavity
Amniotic sac grows faster than the chorionic sac and the they will fuse forming the amniochorionic membrane
what are the two components of the Placenta? and 2 steps to the development of the placenta
Fetal part which is the villious chorion that projects into intervillous space that contains maternal blood
Maternal Part: decidua basalis, endometrium deep to conceptus
Placenta development involves
- formation of chorionic villi (from chorionic sac)
- Proliferation of the cytotrophoblasts
Forming of the primary chorionic villi? and what forms the smooth and villous chorion
Chorionic processes of the cytotrophoblasts that grow into the syncytiotrophoblast layer that form vascular syncytial columns
-appearance marks 1st stage of placental development at end of the 2nd week
will cover the chorionic sac until the 8th week
-villi associate with the decidua capsularis becomes suppressed and degenerate to smooth chorion
Villi associated with the decidua basalis rapidly increase and branch profusely and form buschy area of the chorionic sac the villous chorion
initial process of the forming of the placenta
Cytotrophoblasts of chorionic villi proliferate at chorionic plate
extend through the syncytiotrophoblasts forming the cytotrophoblastic shell
- surrounds the chorionic sac
- attaches and erodes the decidua basalis
- creates the intervillious space
