Establishing a Body Plan III Flashcards
What are the 4 structures classified as extraembryonic tissues? Describe where all 4 came from and what tissues (endoderm/mesoderm/ectoderm) they are composed of.
Yolk Sac- Inner cell mass: hypoblast derivative (Mesoderm and Endoderm)
Amnion- Inner cell mass: epiblast derivative (Ectoderm and Mesoderm)
Allantois- Inner cell mass; interfaces with placenta via the umbilical cord (Mesoderm and Ectoderm)
Chorion- Part of the fetal-maternal interface (Ectoderm and Mesoderm)
What are the 2 structures that make up the Fetal-maternal interface?
Placenta- Trophoblast derivative
Chorion- Trophoblast derivative
What are the 3 functions of the Amnion?
Buffer against mechanical injury
Accommodates growth
Protects fetus from adhesions
What are the 2 clinical correlations associated with the Amnion?
Hydramnios- Related to esophageal atresia and ancephaly
Oligohydramnios- Related to renal agenesis *Note that without the kidneys forming the fetus cannot pee. This pee is a large part on how the amnion is formed. Therefore, no kidneys= little amniotic fluid
Describe the 2 phases in the formation of the amnionic fluid
Phase I: First 20 weeks of pregnancy. Free diffusion of electrolytes through the fetal ectoderm. Secretion by amnionitic membrane
Phase II: Contributions from fetal urine. Filtration from vessels associated with Allantois
Where do Allantoic (Umbilical) vessles develop?
Develop in the mesoderm of the allantois.
What is the proximal part of the allantois called and what does it become?
What is it associated with?
Urachus, which becomes the umbilical ligament and is associated with the urinary bladder
In regards to the Maternal-Fetal blood flow pattern, describe the maternal blood flow pathway
Maternal blood enters intervillous spaces (trophoblastic lacunae) from spiral arteries.
Exchange of materials (respiratory gasses, nutrients, waste products) between maternal blood in lacunae and fetal blood in capillaries in the villi
Maternal blood returns to maternal veins in the decidua basalis
In regards to the Maternal-Fetal blood flow pattern, describe the fetal blood flow pathway
Fetal blood is entirely enclosed within the vessels (this prevents fetal-maternal blood from mixing)
Fetal blood travels to capillary beds within placental villi via umbilical arteries (usually two)
Fetal blood returns from capillary beds within placental villi via the umbilical vein (usually one)
What information can be learned by testing A-fetoprotein in regards to Amniotic fluid?
A high concentration of A-fetoprotein (a protein of the central nervous system) to the amniotic fluid is a strong indicator of a neural tube defect.
What information can be learned by testing Creatine or the Lecithin- to- Sphingomyelin ratio in regards to Amniotic fluid?
Fetal maturity can be assessed by determining the concentration of creatinine or the lecithin- to - sphingomyelin ratio (which is a reflection of the maturity of the lungs)
What tissue in the mature placenta directly interfaces with the maternal uterine connective tissue?
Chorion- composed of the inner cytotrophoblastic shell and the outer syncytiotrophoblast
What is the fate of the decidua capsularis?
The endometrium (lining of the uterus) of the mother is known as the decidua ( cast off ). As the embryo enlarges, the decidua capsularis becomes stretched and smooth. It eventually fuses with the decidua parietalis.
What is hydatidiform mole?
A cluster of fluid-filled sacs formed in the uterus by the degeneration of chorionic tissue around an aborting embryo.
Part of paternal imprinting
What is placenta previa?
A condition in which the placenta partially or wholly blocks the neck of the uterus, thus interfering with normal delivery of a baby.
