Lecture 13: The Bilaminar Embryo

Question 1

three germ tissue types

Answer 1

Ectoderm, mesoderm, endoderm

Question 2

Morula

Answer 2

ball of cells, 32 or after 5 divisions. still embryonic stem cells. As the cells divide, migrate down the fallopian tube towards the uterus

Question 3

Blastocyst

Answer 3

Morula transforms into this by secreting a fluid within the ball, creating a blastocyst cavity. Creates a polar ball, with one highly cellular side and one a-cellular side. Contains embryoblast and trophoblast

Question 4

embryoblast

Answer 4

inner cell mass of blastocyst

Question 5

trophoblast

Answer 5

outer cell wall of blastocyst

Question 6

when does zona pellucida break down?

Answer 6

when blastocyst develops, this allows for implantation

Question 7

When is implantation

Answer 7

5-7 days after fertilization, during the blastocyst phase

Question 8

which side of blastocyst approaches uterus

Answer 8

the side with inner cell mass

Question 9

Syntiotrophoblast

Answer 9

The trophoblast cells invade the endometrium during implantation, in the process become syntiotrophoblast, a multi-nucleated mass that invade the endometrium wall, forming connections with maternal capillaries and glands that will lead to lacunar network. Also release human chorionic gonadotropin, which promotes the LC to continue releasing progesterone which continues pregnancy

Question 10

cytotrophoblast

Answer 10

what remaining trophoblasts differentiate into during implantation, are the surrounding cells of blastocyst after implantation

Question 11

exocoelemic cavity

Answer 11

what blastocyst cavity is called post-implantation. lined with exocoelemic membrane

Question 12

hypoblast cells

Answer 12

line the roof of the exocoelemic cavity, what bottom of inner cell mass embryoblasts differentiates into. Seen as primitive endoderm

Question 13

epiblast

Answer 13

line the amniotic cavity that forms within the former inner cell mass of former blastocyst. primitive ectoderm

Question 14

amniotic cavity

Answer 14

forms within former inner cavity of blastocyst, lined by amnion (membrane)

Question 15

bilaminar embryo

Answer 15

the epiblasts and hypoblasts together form the bilaminar embryo or bilaminar disk

Question 16

heuser’s membrane

Answer 16

other name for exocoelemic membrane, created by migrating hypoblasts from roof of cavity.

Question 17

Primary Yolk Sac

Answer 17

develops from exocoelemic membrane and cavity, exocoelemic membrane now called primary yolk sac endoderm

Question 18

extraembryonic mesoderm

Answer 18

Surrounds amniotic cavity and primary yolk sac and bilaminar embryo, is created by primary yolk sac endoderm

Question 19

Extraembryonic coelem

Answer 19

Spaces form in extraembryonic mesoderm, resulting in extraembryonic coelem surrounding primary yolk sac

Question 20

extraembryonic splanchnic vs. somatic mesoderm

Answer 20

E. splanchnic mesoderm surrounds primary/secondary yolk sac, E. somatic mesoderm lines the extraembryonic coelem

Question 21

Secondary yolk sac

Answer 21

formed when part of primary yolk sac is pinched off to temporarily be within the extraembryonic somatic mesoderm before degenerating. The secondary (or definitive) yolk sac serves as site of early transfer of nutrients, health blood development, and provides primordial germ cells

Question 22

prechordal plate

Answer 22

Develops as thickened area of hypoblasts in a localized area of bilaminar embryo, determines chordal-caudal polarity, site of mouth