Placenta Flashcards
Describe the fetal and maternal component of the placenta
The fetal component is the villous chorion (chorionic villi)
The maternal component: decidue basalis
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Explain the formation of the chorionic villi
The fetal component of the placenta is derived from the cytotrophoplast and the extraembryonic mesoderm, forming the villous chorion.
Primary= cytotrophblast invading syntio
secondary = extaembryonic mesoderm invading the primary villi
Explain the structure of the placental membrane and how it changes throughout pregnancy
Initially (by month 4), the outer surface of the terminal villi form a placental membrane that consists of 4 layers:
Syncytiotrophoblast
Cytotrophoblast
Extraembryonic mesoderm
Fetal endothelium
By the beginning of month 4, the cytotrophoblast degenerates, leaving only 2 layers in the placental membrane:
Syncytiotrophoblast
Fetal endothelium
The intervillous space of the placenta contains
maternal blood
Discuss the formation of chorion leave and frondosum
Once you make the chorionic villi the fetal blood supply that develops the chorionic frondosum is just super thick and bushy villi that are at the part where the fetus is anchored in the moms endometrium.
Name the structures covered by the amnion
Name the structures covered by amnion
Fetus, umbilical cord and placenta
What are the functions of the amniontic fluid?
Functions: Allows for fetal movements
prevents adherence between amnion and embryo
Shock absorber
Barrier to infection
Promotes lung development
What are the orgins of the amniotic fluid?
Initially, amniotic fluid is secreted by cells of the amnion and some is derived from maternal blood, tissue and interstitial fluid by diffusion. Beginning in the 11th week, the fetus contributes to the amniotic fluid by excreting urine into the amniotic cavity.
What is the amnio-chorionic membrane?
As the volume increases, the amnion is pushed against the chorion and the chorionic cavity is obliterated such that the amnion lies against the chorionic laeve to form the amnio-chorionic membrane (this is the “water-bag” that breaks prior to the delivery of the baby)
Describe amniocentesis and its indications
In amniocentesis a hollow needle is inserted through the abdomen into the uterus, and the amniotic fluid is drawn for analysis. Is used to test for genetic or chromosal abnormalities. Also paternity testing and fetal lung testing.
Describe the formation of amniotic bands
Tears in the amnion may result in amniotic bands that encircle the fetal limbs or digits resulting in deformations.
Describe polyhydranios and oligohydramnios
Polyhydarmnios: excess amniotic fluid. Causes: Maternal diabetes and disorders of the central nervous system and GI tract that prevent the fetus from swallowing the amniotic fluid
Oligohydramnios: too little amniotic fluid; may result from failure of the fetal kidneys to form or amniotic fluid leakage. Severe oligohydramnios early in pregnancy is a risk factor for lung hypoplasia (lung underdevelopment)
What is the normal amount of amniotic fluid at term?
1000 mL
