Flashcards in Extraembryonic Tissues And Placenta Deck (19):
What are the two trophoblastic derivatives that comprise the fetal-maternal interface?
What are the functions of the amnion?
-buffer against mechanical injury
-allows normal movements
-protects fetus from adhesions
What is hydramnios?
-too much amniotic fluid which could be due to an esophageal atresia or brain damage
What is oligohydramnios?
-deficiency of amniotic fluid possibly due to infant not able to excrete urine back into the amnion -> renal agenesis
How many phases are there in the formation of amniotic fluid?
What happens during phase I of formation of amniotic fluid?
-first 20 weeks of pregnancy
-free diffusion of electrolytes through fetal ectoderm
-secretion by amniotic membrane
What happens during phase II of the formation of amniotic fluid?
-contributions from fetal urine
-filtration for vessels associated with chorion laeve
What some functions of the yolk sac?
-may concentrate: folic acid and vitamins (A, B12, and E)
-site of primordial germ cells
-location of blood islands -> origin of initial blood cells (extraembryonic hematopoiesis
Where do the umbilical/allantoic vessels develop?
-mesoderm of the allantois
How is the allantois associated with the bladder?
-proximal part of allantois is urachus which becomes the median umbilical ligament
What are the stages of placental development?
-primary villous stage
-secondary villous stage
-tertiary villous stage
What characterizes the previllous stage?
-no villi have been formed on the trophoblast
What characterizes the primary villous stage?
-solid, cytotrophoblastic, ectodermal primary villi appear
What characterizes the secondary villous stage?
-mesodermal cores appear within the primary villi
What characterizes the tertiary villous stage?
-characterized by the appearance of blood vessels within the mesenchymal core of the secondary villi
What is formed during the final development of the placenta?
-cytotrophoblastic shells: formed by expansion of columns over the maternal decidua L cells
-anchoring villi: villi anchored to the shell as opposed to floating villi
What are the four extraembryonic layers and what are their germ layer derivatives?
-amnion (ICM -> epiblast)
-yolk sac (ICM -> hypoblast)
-chorion (part of fetal maternal interface)
-allantois (ICM -> interfaces with placenta via umbilical cord)
Describe the blood flow from the maternal side.
-maternal blood enters intervillous spaces (trophoblastic lacunae) from spiral arteries
-exchange of materials between maternal blood in lacunae and fetal blood in capillaries in the villi
-maternal blood returns to maternal veins in the decidua basalis