2nd week of development (quiz 5)

Question 1

In the second week of development, as implantation of the blastocyst occurs, morphologic changes in the embryoblast produce a ______________________________ composed of epiblast and hypoblast.

Answer 1

bilaminar embryonic disc

Question 2

In the 2nd week of development, what does the embryonic disc give rise to?

Answer 2

the germ layers

Question 3

Extraembryonic structures forming during the 2nd week are the:

Answer 3

-amniotic cavity
-amnion
-umbilical vesicle connecting stalk
-chorionic sac

Question 4

Syncytiotrophoblast is formed once a blastocyst touches the…..

Answer 4

endometrium

Question 5

The syncytiotrophoblast enters the endometrial connective tissue lining the uterus through the process of…..

Answer 5

interstitial invasion

Question 6

The blastocyst slowly becomes embedded in the endometrium, which stop proliferating. Syncytiotrophoblastic cells displace endometrial cells at the implantation site. The endometrial cells undergo ____________, which facilitates the invasion. The CT cells around the implantation site accumulate glycogen and lipids and assume a polyhedral shape. Some of these cells are called ______________ (glycogen/lipid storing vesicles) and degenerate adjacent to the penetrating syncytiotrophoblast. The syncytiotrophoblast engulfs these cells, providing a rich source of embryonic nutrition

Answer 6

apoptosis, decidual cells

Question 7

What is an essential hormone for pregnancy?

Answer 7

hCG (human chorionic gonadotropic hormone), also known for pregnancy tests

(enough hCG is produced by the syncytiotrophoblast at the end of the 2nd week to give a positive pregnancy test)

Question 8

The syncytiotrophoblast produces a glycoprotein hormone- hCG, which enters the maternal blood via isolated cavities called ____________ in the syncytiotrophoblast

Answer 8

lacunae

Question 9

hCG maintains the hormonal activity of the _____________ in the ovary during pregnancy

Answer 9

corpus luteum

Question 10

As implantation of the blastocyst progresses, a small space appears in the embryoblast, which is the….

Answer 10

primordium of the amniotic cavity

Question 11

_____________ separate from the __________ and form the amnion which encloses the amniotic cavity

Answer 11

Amnioblasts, epiblast

Question 12

Concurrently, changes occur in the embryoblast that creates a flat, almost circular bilaminar plate of cells, the _________________, which consists of 2 layers. The epiblast is the thickest layer consisting of high columnar cells related to the amniotic cavity. The hypoblast consists of small cuboidal cells adjacent to the exocoelomic cavity

Answer 12

embryonic disc

Question 13

The pluripotent ____________ forms the floor of the amniotic cavity and is continuous peripherally with the amnion

Answer 13

epiblast

Question 14

The hypoblast forms the roof of the exocoelomic cavity. This membrane, together with the hypoblast, lines the __________________

Answer 14

primary umbilical vesicle (yolk sac)

Question 15

As the amnion, embryonic disc, and umbilical vesicle form, lacunae (small spaces) appear in the….

Answer 15

syncytiotrophoblast

Question 16

As the amnion, embryonic disc, and umbilical vesicle form, lacunae (small spaces) appear in the syncytiotrophoblast. The lacunae become filled with __________________. The fluid in the lacunar spaces, embryotroph, passes the embryonic disc by diffusion and provides nutritive material to the embryo

Answer 16

maternal blood

Question 17

Syncytiotrophoblastic lacunae fuse to form lacunar networks giving it a ________________ appearance

Answer 17

sponge-like

Question 18

The endometrial capillaries around the implanted embryo become congested and dilated to form….

Answer 18

maternal sinusoids (bigger swollen capillaries that become leaky)

Question 19

The syncytiotrophoblast erodes the ____________, and maternal blood flows freely into the lacunar networks. The trophoblast absorbs nutritive fluid from the lacunar networks, which is transferred to the embryo.

Answer 19

sinusoids

Question 20

A new population of cells appears between the inner surface of the ______________ and the outer surface of the exocoelomic cavity. These cells are derived from yolk sac cells which form a fine, loose CT and the extraembryonic mesoderm eventually fills all the space between the trophoblast externally and the amnion and exocoelomic membrane internally

Answer 20

cytotrophoblast

Question 21

The ________________________ increases in size and thickness and the isolated extraembryonic coelomic spaces appear within it. These spaces rapidly fuse to form a large isolated cavity, the extraembryonic coelom. This fluid-filled cavity surrounds the amnion and umbilical vesicle

Answer 21

extraembryonic mesoderm

Question 22

As the extraembryonic coelom forms, the ________________________ decreases in size and a smaller secondary umbilical vesicle forms (secondary is just below the primary vesicle).

Answer 22

primary umbilical vesicle

Question 23

The end of the 2nd week of development is characterized by the appearance of….

Answer 23

primary chorionic vili (this is the start of trying to form the placenta)

Question 24

The end of the 2nd week of development is characterized by the appearance of primary chorionic vili. The cellular extensions grow into the syncytiotrophoblast in the 1st stage of development of the chorionic villi of the _________

Answer 24

placenta

Question 25

The extraembryonic coelom (space) splits the extraembryonic mesoderm into 2 layers. The extraembryonic __________ mesoderm lines the trophoblast and covers the amnion. While the extraembryonic ______________ mesoderm surrounds the umbilical vesicle

Answer 25

somatic, splanchnic

Question 26

The extraembryonic somatic mesoderm and the 2 layers of trophoblast form the __________, which forms the wall of the chorionic sac. Measuring the diameter of the chorionic sac is valuable for evaluating early embryonic development and pregnancy

Answer 26

chorion

Question 27

A 14 day embryo still has the form of a flat bilaminar embryonic disc but the hypoblastic cells in a localized area are now columnar and form a circular area, called the ____________ plate. This plate indicates an important organizer of the head region

Answer 27

prechordal

Question 28

Implantation of ______________ usually occurs in the uterine endometrium in the superior part of the body of the uterus

Answer 28

blastocysts

Question 29

Blastocysts sometimes implant outside of the uterus (______________). These implantations result in ectopic pregnancies; 95-98% of ectopic implantations occur in the uterine tubes, most often in the ampulla and isthmus

Answer 29

ectopic sites

Question 30

Read the summary slide of week 2 development

Answer 30