MCP 23: Implantation and Germ Layer

Question 1

trophoblast

Answer 1

11 cells on the outside of the morula that are in contact with the environment, differentiates into two tissues when contacts endometrium

Question 2

implantation 5-9 days

Answer 2

1.) when blastocyst reaches endometrium, attached via the embryonic pole 2.) trophoblast cells begin to dissolve connections between endometrium cells and form syncytiotrophoblast 3.) endometrium grows around the embryo (decidual reaction) 4.) ICM develops into two layers (epiblast and hypoblast) 5.) epiblast amniotic cavity forms 6.) cells from hypoblast travel along cytotrophoblast to surround blastocel 6.) syncytiotrophoblast continues to invade endometrium 7.) tropoblastic lacuna form

Question 3

abembryonic pole

Answer 3

pole opposite the ICM on the implanted embryo

Question 4

decidual reaction

Answer 4

endometrium growns around embryo

Question 5

cytotrophoblast

Answer 5

trophoblasts retrain their plasma membranes on the abembryonic pole, also a thin layer of cytotrophoblast between the syncytiotrophoblast and the derivatives of the inner cell mass

Question 6

epiblast

Answer 6

layer closest to the syncytiotrophoblast (AKA the primative ectoderm), this portion of the ICM will form the embryo, all 3 germ layers

Question 7

hypoblast

Answer 7

layer furthest from the syncytiotrophoblast, facing the blastocoel, will form the yolk sac, sometimes the hypoblast is called the primitive endoderm

Question 8

bilaminar disk

Answer 8

epiblast and hypoblast together

Question 9

amniotic cavity

Answer 9

second fluid-filled space formed by the epiblast

Question 10

tropoblastic lacuna

Answer 10

fluid filled spaced in syncytiotrophoblast where mother’s blood washes embryo’s blood

Question 11

implantation days 8-12

Answer 11

1.) embryo continues to grown 2.) hypoblast stops migrating 3.) Heuser’s membrane formed 4.) extraembryonic reticulum forms between blastocoel and cytotrophoblast 5.) trophoblastic reticulum begin to fill with mother’s blood 6.) cells in extraembryonic membrane signal cells in epiblast to migrate along path between cytotrophoblast and extra embryonic reticulum 7.) extraembryonic reticulum dissolves and replaced by chlorionic cavity 8.) chorionic cavity causes extrembryonic mesoderm to split primary yolk sac into two parts

Question 12

Heuser’s membrane

Answer 12

thin layer of cells that hypoblast forms between blastocoel and cyctotrophoblast

Question 13

extraembryonic reticulum

Answer 13

thick, gelatinous structure between cytotrophoblast and Heuser’s membrane, eventually replaced by chlorionic cavity after extraembryonic mesoderm separates it from cytotrophoblast and Heuser’s membrane

Question 14

primary yolk sac

Answer 14

when Heuser’s member and extraembryonic reticulum have formed

Question 15

extraembryonic mesoderm

Answer 15

cells from epiblast that migrate between cytotrophoblast and extraembryonic reticulum , NOT part of the embryo proper, eventually completely surround extraembryonic reticulum when migration has ceased

Question 16

chorionic cavity

Answer 16

replaced extraembryonic reticulum after extraembryonic mesoderm forms, filled with saline

Question 17

secondary yolk sac

Answer 17

AKA definitive yolk sac, yolk sac split by cholionic cavity growth that surrounds developing embryo, embryonic mesoderm that surrounds secondary yolk sac for first blood vessels in developing embryo

Question 18

primary stem villus

Answer 18

syncytiotrophoblast has invaded mother’s endometrium, trophoblastic lacunae in syncytiotropholbasts that are pooled with mother’s blood, layer of thin cytotrophoblast underneath syncytiotrophoblast, then underneath that is exposed extraembryonic mesoderm

Question 19

secondary stem villus

Answer 19

extraembryonic mesoderm and cytotrophoblast push down into syncytiotrophoblast, no tissue layers are broken

Question 20

tertiary stem villus

Answer 20

when secondary stem villus have pushed down into the maternal endometrium, occurs 21 days after fertilization and is the start of the fetal circulatory system, creates blood barrier between fetus and mother

Question 21

ectopic pregnancy

Answer 21

when embryo implants at the incorrect site, most common site is the ampulla region, other possible locations include isthmus of the uterine tube, abdomen, cervix, ovary and fimbrae, surgery usually required, symptoms include vaginal bleeding and pain

Question 22

pre-eclampsia

Answer 22

caused by shallow implantation of the embryo, present in 5% of pregnancies and causes 20% of birthing complications\

Question 23

hydatiform mole

Answer 23

cyst composed only of placental tissue, no fetus present and common in mothers under 25 y/o, symptoms include vaginal bleeding, hypertension, edema, and abnormally high levels of hCG

Question 24

molecular mechanism of pre-eclampsia

Answer 24

VEGF stimulates blood vessel growth by binding to Flt-1 on the surface of endothelial cells. There is also a soluble form of the receptor, sFlt-1, that competes for VEGF. sFLT-1 is usually present in small amounts. During pregnancy PLGF (placental growth factor) also stimulates vessel growth by binding to Flt-1. Women have elevated sFLT-1 levels five weeks before showing symptoms of pre-eclmapsia, since sFLT-1 is soluble and travels all over the body sopping up VEGF and PLGF–causes inadequate vessel formation.

Question 25

treatment for pre-eclampsia

Answer 25

flooding mother with PLGF to prevent sFLT-1 from sopping it up