Extraembryonic Tissues And Placenta Flashcards Preview

Embryology Exam II > Extraembryonic Tissues And Placenta > Flashcards

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

-accommodates growth

-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

-maternal serum

-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

-other sources?


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?

-previllous embryo

-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 columns

-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


Describe the fetal blood flow.

-fetal blood is enclosed within vessels

-fetal blood travels to capillary beds within placental villi via umbilical arteries (2)

-fetal blood returns from capillary EDs within placental villi via umbilical vein (1)