2nd week of development (quiz 5) Flashcards
In the second week of development, as implantation of the blastocyst occurs, morphologic changes in the embryoblast produce a ______________________________ composed of epiblast and hypoblast.
bilaminar embryonic disc
In the 2nd week of development, what does the embryonic disc give rise to?
the germ layers
Extraembryonic structures forming during the 2nd week are the:
-amniotic cavity
-amnion
-umbilical vesicle connecting stalk
-chorionic sac
Syncytiotrophoblast is formed once a blastocyst touches the…..
endometrium
The syncytiotrophoblast enters the endometrial connective tissue lining the uterus through the process of…..
interstitial invasion
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
apoptosis, decidual cells
What is an essential hormone for pregnancy?
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)
The syncytiotrophoblast produces a glycoprotein hormone- hCG, which enters the maternal blood via isolated cavities called ____________ in the syncytiotrophoblast
lacunae
hCG maintains the hormonal activity of the _____________ in the ovary during pregnancy
corpus luteum
As implantation of the blastocyst progresses, a small space appears in the embryoblast, which is the….
primordium of the amniotic cavity
_____________ separate from the __________ and form the amnion which encloses the amniotic cavity
Amnioblasts, epiblast
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
embryonic disc
The pluripotent ____________ forms the floor of the amniotic cavity and is continuous peripherally with the amnion
epiblast
The hypoblast forms the roof of the exocoelomic cavity. This membrane, together with the hypoblast, lines the __________________
primary umbilical vesicle (yolk sac)
As the amnion, embryonic disc, and umbilical vesicle form, lacunae (small spaces) appear in the….
syncytiotrophoblast
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
maternal blood
Syncytiotrophoblastic lacunae fuse to form lacunar networks giving it a ________________ appearance
sponge-like
The endometrial capillaries around the implanted embryo become congested and dilated to form….
maternal sinusoids (bigger swollen capillaries that become leaky)
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.
sinusoids
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
cytotrophoblast
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
extraembryonic mesoderm
As the extraembryonic coelom forms, the ________________________ decreases in size and a smaller secondary umbilical vesicle forms (secondary is just below the primary vesicle).
primary umbilical vesicle
The end of the 2nd week of development is characterized by the appearance of….
primary chorionic vili (this is the start of trying to form the placenta)
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 _________
placenta
