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Flashcards in Bilaminar& Trilaminar Deck (63):

________ occurs before completion of oocyte maturation. The____ _____ is released from the ovary and is arrested in _____ of the ____  _____ division. The secondary oocyte is surrounded by the _______ _____   and ____ _____.


  • ovulation
  • secondary oocyte 
  • metaphase of the second meiotic division
  • zona pellucida
  • corona radiata


In order for fertilization to occur, the ___ ____ and ____ ____ must be penetrated by the sperm. What is each layer? 


  • Zona pellucida:   a thin transparent gelatinous layer of protein and polysaccharides
  • -Corona radiata :  several layers of ovarian follicle


What is capacitation?

Capacitation is the functional changes that sperm undergoin the female reproductive tract that enable them to fertilize a secondary oocyte.


After capacitaion, the overlying sperm ___ ___  becomes unstable when ___ ____ and ____ ___ _____ are removed from plasma membrane overlying the sperm’s _____ (modified ____ ); enzymes are then released (______)  or are exposed (____) to help the sperm to penetrate corona radiata and zona pellucida.

  • plasma membran
  • glycoprotein coat
  • seminal plasma proteins
  • acrosome
  • lysosome
  • hyaluronidase)
  • acrosin


Steps in Fertilization

First, the Sperm must penetrate the ______ ____ & ____ ____. Next,  the fusion of ___ and ____ _____ ____ occurs. When a sperm enters the egg, it triggers changes that prevent _____ which is the _____________________. A _____ reaction occurs and the oocyte membrane becomes _____ to other sperm. The ____ reaction occurs and the  Zona pellucida alters its structure to prevent ____ ____ and _____. Next, formation of male _____ occurs; the _____ and ______ of the sperm degrade, so that all mitochondria in the embryo (and all mitochondrial DNA) come from the ____. When sperm is in the egg, the Completion of ___ ___ ___ of oocyte and formation of f___ ____ occurs; the chromatin will ___. Lastly, ____ occurs and ___ _____is formed 

  1. corona radiata and zona pellucida
  2. sperm and oocyte plasma membranes
  3. polyspermy
  4. fertilization of an egg by more than one sperm)
  5. cortical
  6. impenetrable
  7. Zona
  8. sperm binding and penetration
  9. pronucleus
  10. tail and mitochondria
  11. mother
  12. f second meiotic division
  13. female pronucleus
  14. Unravel
  15. syngamy
  16. diploid zygote


What is syngamy?

syngamy-fusion of nuclear material of egg and sperm


Following fertilization, (takes about _-_hrs), the diploid  zygote undergoes a series of mitotic cell divisions, called _____, as it migrates toward the uterus. The process of cleavage divides the zygote’s _____ into increasingly smaller cells known as _____ . After the third cleavage, the blastomeres will tightly ____ via _______ &_____ on  the surface via a process known as _____.

  • 12-24
  • cleavage
  • blastomere
  • cytoplasm
  • blastomeres
  • align
  • tight junctions
  • CAMs
  • compaction


______- are totipotent which means?

blastomeres- which means they can become any cell or a complete embryo


About 3 days after fertilization,  (12-32 cell stage), the embryo is termed a _____ that is made of ______. The morula consists of a ___ ___ of cells with an___ and ____ ____ ____. The morula enters the uterus by day ___.

  • morula
  • blastomeres
  • solid ball
  • inner and outer cell mass
  • 4


The inner and outter cell masses occur when the cells are a ______. The inner cell mass will become the ______ while the outer cell mass will become part of the ____ part of ____.

  • morula
  • embryo
  • embryonic part of placenta


Fluid from the  _____ will penetrate the zona pellucida into the ____ to form a hollow cavity, transforming the ____ into a _____. The inner and outer cell masses are visible now.


  • uterus
  • morula
  • morula
  • blastocyst


When fluid from the uterus penetrates the zona pellucida and creates the blastocyst from the morula, the fluid filled cavity separates the blastomeres of the inner and outer cell mass into 2 regions. The outer cell mass is the  ____ and the inner cell mass is the  _____.

  • trophoblast
  • embryoblast


  The trophoblast makes___ ___ ____ (___) which is the basis for ____ _____; hCG acts on ____ to form ____ ____ so the ovary can make _______ and the pregnancy can be sustain ____ until ____ is developed. hCG increases over time


  • human   chorionic gonadotropin   (hCG)
  • pregnancy tests
  • ovary
  • corpus ludeum 
  • progesterone
  • sustained 
  • placenta


About 2 days after entering the ____, the blastocyst sheds its ___ ____ and “hatches” allowing the blastocyst to ____. ____ on the outer cell mast has will help it attach to the ____ _____ at its ____ ___ (side where the embryoblast is located)

  • uterus
  • zona pellucida
  • grow
  • CAM
  • uterine endometrium
  • embryonic pole


Abnormal ___ do not usually show any sign of pregnancy because if the trophoblast is defective, no ___ will be produced to support the ___ ___ and pregnancy. 

  • blastocyst
  • hCG
  • corpus luteum


Hydatidiform Moles can lead to a ___ ___; these are due to an abnormality in the ____ specifically the ___ that causes the ____ to be overactive and replicated. This usually results in a ____ ____. 

Molar pregenacy

abnormal blastocyst 



 spontaneous abortion 


After hatching, in the area over the _______ the trophoblast differentiates into 2 layers: the inner layer is the _____; it consists of ____ _____ with mitotic capacity and helps form part of ____ as well as functions as an _____. The outer ____ zone that forms from the trophoblast is the _________; this zone will invade the _____ ____ to implant the _______; it helps erode the _____ ___ so the ____ can get near the ____ ____ and set up the ____. The synctiotrophoblast will also produces ____  which enters the maternal blood via ______

  • embryoblast
  • Cytotrophoblast:
  • mononucleated cells 
  • placenta
  • anchor
  • multinucleated
  • synctiotrophoblast
  • urterine endometrium
  • blastocyst
  • uterine wall
  • embryo
  • uterine wall blood
  • placenta
  • hCG
  • lacunae


Implantation is completed by the end of week ___. The Site of implantation is marked temporaily by a ___/____ ____



fibrin(coagulation) plug


If the blastocyst is implanted to close to the internal opening of the ____, then ______ ____ may occur. ______ ____ ____ may occur in the later stages of the pregnancy. A normal, vaginal birth with this type of implantation could increase risk of ____ mom; a _______ may be needed. The baby may be ______.

  • cervix
  • placenta previa
  • painless vaginal bleeding 
  • hemmorage
  • c-section
  • premature


If a blastocyst is implanted outside of the uterus it is called and ____ ____. Most of these occur in the ____ ___ (___ pregnancy)  which is not viable for the ___ and the _____ will have complications.   Ectopic pregnancy

95% of ectopic pregnancies occur in the uterine tube (tubal pregnancy)- not viable for embryo and mom has troubles coming

Signs and symptoms of pregnancy, with abdominal pain and tenderness

May also implant in the abdominal cavity, often in the rectouterine pouch, or pouch of Douglas.

Mom can survive, but fetus usually doesn’t. 

  • ectopic preg.
  • uterine tube
  • tubal
  • embryo
  • mom


In week two of development, the embryoblast will differentiates into 2 cellular layers, what are they?


-dorsal epiblast

-ventral hypoblast



The epiblast will eventually become a ____ ____; it goes on to form all of the ____, _____, and _____ layers.

human being






The ventral hypoblast (becomes the ____ area) acts as a ____ ____ ___ and eventually goes away. 


temporary place holder



 Within the epiblast,clefts develop to form the _____ ____ and _____.  _____ ____ will migrate and line the inner surface of the _____, forming the exocoelomic membrane (aka _____ _____) which surrounds a space known as the ____ ___ ____. 

amniotic cavity and amnion

Hypoblast cells


Heuser’s membrane

primitive yolk sac


The extraembryonic mesoderm proliferates to fill the space between the _______ and either the _____ or the ____ __ ___ (aka _____). 



primitive yolk sac

primary umbilical vesicle



The outer cell mass is called the _____; the cellular ;ayer of the trophoblast is called the ______ whereas the invasive layer that burrows into the uteran wall is called the _______.

  • trophoblast
  • cytotrophoblast
  • syncytiotrophoblast


Label 1-4 and tell me what they were derived from:

Q image thumb

1&2 are derived from trophoblast(OCM) and 3&4 are derived from the embryoblast(ICM).


  1. syncytiotrophoblast
  2. cytotrophoblast
  3. hypoblast
  4. epiblast (notice it's closer to potential blood supply)

A image thumb

When the embryoblast devides, the position is so that the back of the embryo (or _____ side) will be along the ______ while the belly portion (or ____ side) will be along the ______.

  • dorsal
  • epiblast
  • ventral
  • hypoblast


As the soon to be embryo begins implantation, it gets all its nutrients from _____ of _____ secretions; it has no ____ ___. As it grows, this will not be able to sustain the embryo any longer and it must find blood supply. As implantation reaches completion due to the ______ eroding away at the _____ ___ and allowing the embryo to completely implant inside, the _____ will eventually reach & erode some _____ ___ ____ so they spill their blood into _____ within the syncytiotrophoblast. The goal is to get the maternal blood closer and closer to the soon to be embryo. 

  • diffusion
  • uteran 
  • blood supply
  • syncytiotrophoblast
  • uteran wall
  • syncytiotrophoblast 
  • maternal blood vessels
  • lacunae


The Epiblast does eventually become the _____, but it also makes the _____. This is a ____ ___ that forms after spaces arise in the epiblast to create the ____ ____ while the ____ portion of the epiblast forms a thin layer that becomes the _____. This will eventually surround the baby. 

  • human
  • amnion
  • fetal membrane
  • amnionic cavity
  • upper
  • amnion


The _____ is intrumental in forming the gut tube. It is a temporary structure that provides a ____ so its cells are _____ and go through several rounds of ____. The HB will create a ____ ___ ___ first that will get pushed out of the way by a second HB based sac called the _____ ____ ___ that becomes the _____ ____. 





primitive yolk sac

definitive yolk sac

gut tube


This picture shows the formation of the _____ ______(Heuser’s membrane). The ____ ____ are migrating along and lining the ____ surface of the _______ to reach each other so they can form the membrane that will surround the primitive yolk sac

Q image thumb

exocoelomic membrane

hypoblast cells





Several layers are needed for the formation of the placenta, so another layer forms between the exocoelomic layer and the _____ called the _______ ______. This layer is a mesodermal layer that is outside of the _____ proper and will eventually contain ___ ____ to aid in embryonic circulation. 

  • cytotrophoblast
  • Extraembryonic mesoderm

  • embryp

  • blood vessels


After the Extraembryonic mesoderm forms, it begins to breakdown and accumulate _____ within it that become another cavity called the ___ ___


chorionic cavity


During the second week of development what two cavities are formed?

  • amniotic
  • chorionic


The chorion proper is several layers of ___ that form the ___ between ___ ___ and ___ ___.



maternal blood

fetal blood


The chorionic cavity does not extend all the way around, instead a little bit of  _____ _____ is left at the ______ ______ and this will form the ____ _____ which will form the future _____ ______.


extraembryonic mesoderm

embryonic pole

connecting (body) stalk

umbillical cord


The chorionic plate consists of:

extraembryonic mesoderm


a little syncytioblast


As the placenta is forming and growing, the cytotrophoblast proliferates to form extensions called ____ ____ that grow into the overlying_______ to act as anchors. These primary villi grow out into the lacunae, carrying with them a covering of synctiotrophoblast

primary villi





A primary villus contains:

proliferation of cytotrophoblast that makes the body

extraembryonic mesoderm



 During week 3, extraembryonic mesoderm cells invade the ______ pegs, transforming _____ ___ to _____ ___ with a ______ _____. 

By the end of week 3, the extraembryonic mesoderm in the core of the secondary villi will differentiates into ____ ____, forming the ____ ____. 

Now, fetal blood will be traveling through the ___ ___ through____ ____ and circulate fdown through the stem villi so ____ ____ can diffuse through the _____ ____ and go out through the mothers blood and it can get nutrients and oxygen from moms blood as well, but a barrier remains between them. 

cytotrophoblast pegs

primary villi

secondary villi 

mesoderm core. 

blood vessels (arteries and veins)

tertiary villus

embryonic body

umbillcal vessels

metabolic waste

chorionic plate


The process by which we change a Bilaminar (two layer) embryo into a trilaminar (three layer) embryo is called _____. this begins in week __. This gives rise to the ___ ___.







The ectoderm gives rise to the?


ECTO-NS and skin



This is at the begining of _____ in week _

Q image thumb

gastrulation week 3

  1. epiblast
  2. hypoblast
  3. amnionic cavity
  4. buccopharyngeal membrane
  5. primitive pit
  6. primitive node
  7. primitive groove
  8. streak
  9. cloacal membrane


Why is the buccopharyngeal membrane significant?

this is where the mouth and the primitive throat will form. This is the rostral end of the embryo.


why is the cloacal membrane important

this is where the anus will form at the caudal end


What are the two exceptions in gastrulation that do not go to turn into trilaminar structures? why? Why does the rest of the body turn to trilaminar?

the buccopharyngeal and cloacal membranes because they need to be easy to open, whereas the rest of the body needs stability.



How is gastrulation first indicated in week 3?

First indicated by the appearance of the primitive streak on the surface of the epiblast


during gastrulation, ____ cells from the surface become mobile are going to migrate in to the ______, drop down through it, then they will spread out and form the _____ layer, then the_____ layer, and the epiblast that stays on top to become _____.


primitive groove

endodermal layer

mesodermal layer



During gastrulation, The ____ ____ and ___ ____have cells that migrate through them to form structures in the head.



primitive node

prim. pit



Over time, the _____ _____ "regresses caudally" or gets ____ smaller and evntually goes away as the cells of the embryonic disk are getting bigger.

primitive groove



Once the epiblast cells have migrated down through the primitive groove, some will push the _____ out of the way, creating ____ that will form the lining of the futur___ ____ and gut derivatives.

The next generation of cells to come through the groove come to lie between _____ and ____ to form_____ ______.

After the endoderm and mesoderm layers are formed, cells remaining in the____ become _____



gut tube



intraembyronic mesoderm




Some of the cells that go through ____ ___ and up to the ______ ____ will go to form the ____ ____ that is an organizing center for structures in the head.

Afterwards, cells will migrate through the Prim. pit to form the _____ which is the basis for the ____ ____. 


primitive pit

buccopharyngeal membrane

precortal plate


vetebral column


______ ____ are remnents of the notocord

intervetebral disks


The notocord is important bc it releases ____ ____ to make the ectoderm turn into the___ ____ ____.

inducing factors



Conjoined twins result from what?

partial splitting of the primitive node and streak


Sirenomelia or ____ _____ is due to an _____ amount of _____ being formed in the ____ region of the embryo. The lower limbs are ____ __ and the ____ & _____ development is usually affected so negatively that the babies will not survive.


mermaid syndrome




fused together

kidneys and bladder


Sacrococcygeal Teratoma occurs when? 

These commonly contain tissues derived from?


  • Remnants of the primitive streak in the sacrococcygeal area
  • -Commonly contain tissues derived from all 3 germ layers

****So cells keep going through it and these tumors contain stuff from all three germ layes (like hair, teeth could be in them)


What is the most common tumor for newborns?

Sacrococcygeal Teratoma


_____ is a tumor that arises from remnants of notochord. It is usually found ____ or _____ and found in ____ ___ patients. (around 50)


intracranially or sacrally

older men


During week 4 of development, the folding of the embryo occurs in 2 planes. One plane is ____________ (_____) and the other is ______ (______). The folding creates an _____ “tube” within an _____ “tube” and transforms the layer of endoderm into _____ _____. The tube closes at the ventral, or at the belly, surface of embryo

cranio-caudal (head-tail)

Transverse (lateral)



primitive gut


If complete lateral folding fails to occur, a birth defect called ______ results. This happens in 1 in 5,000 live births. It is an ____ ___ ____, characterized by an opening in the ____ ___of the fetus. Intestines and other abdominal organs ____ (_____) through the opening the abdominal wall and spill out into the ____ ____ around the fetus.


abdominal wall defect

abdominal wall

herniate (protrude) 

amniotic fluid