Embyology Flashcards
When does ovulation happen
14 days into ovarian cycle
Ovulation process
1 oocyte released from ovary, swept up by fimbriae into the oviduct (uterine tube/fallopian tube)
Sperm travel time cervix to oviduct
30 minutes to 6 days
Results of fertilization
Zygote
Diploid number of chromosomes
Gender determination
Cleavage initiated
XX gender, XY gender
Female, male
How many hours in does cleavage happen
30 hrs
After fertilization, the zygote divides by ____ to produce 2 cells, then 4, then 8, etc
After the 16 cell stage, what is the group of cells called?
Mitosis, morula
At what point in time does the fertilized cell become a morula
3 days
At what point in time does the zygote become an ADVANCED morula
Around 4 days
The morula turns into _____ by developing into a ____ ball of cells with an inner protrusion called a
Blastocyst, hollow, inner cell mass
At what stage (aka what form of the cell) is the uterus entered
Blastocyst
At what stage (aka what form of the cell) is the uterus entered
Blastocyst
The blastocyst implants into the
Endometrium
How long after fertilization does implantation happen
7 days
What is the syncytiotrophoblast
The part of the blastocyst that implants into the endometrium
*looks like fingers reaching into endometrium
When do the trophoblast and embryoblast each differentiate into multiple layers?
Week two
What are the two layers of the trophoblast
Cytotrophoblast and syncytiotriphoblast
What are the two layers of the embryoblast
Epiblast and hypoblast
What is a pregnancy test recognizing (hormone and structure)
Human chorionic gonadotropin from the synctioblast
On day ___, two cavities form called the
9, amnionic cavity (middle of epiblast) and the exocoelomic cavity (primitive yolk sac)
The amnionic cavity eventually is
The space where the fetus develops
On day 12, the _____ forms
Extraembryonic mesoderm
The layer of the extraembryonic mesoderm that is closest to the yolk sac ? Farther?
Splanchnic , somatic
At 13 days, the ____cavity forms
Chorionic
Gastrulation happens in week
3
Gastrulation definition
Converts the bilaminar embryo into the trilaminar embryo
Germ layers produced by Gastrulation …
Ectoderm, mesoderm, endoderm
The ectoderm develops into
Neural system, skin and appendages that relate to external environment (eyes, ears)
Mesoderm develops into
Musculoskeletal tissue, limb buds, genitourinary system, body wall and membranes that line cavities
Endoderm develops into
Foregut, midgut, hindgut, GI tract and appendages (liver, pancreas), respiratory tract, bladder
Endoderm replaces the
Hypoblast
Ectoderm come from the
Epiblast
Epiblast cells migrate through the ______ and _______ towards the _____ membrane
Primitive node, streak, oropharyngeal
The future mouth forms from the
Oropharyneal membrane
The future anus comes from the
cloacal membrane
What is holoprosencephaly? what causes it?
Injury to the anterior midline of germ disc (around the oropharyngeal membrane)
High does alcohol?
Genetics
What is caudal dysgeneis? What causes it?
Injury to the caudal aspect of the germ disc (near the cloacal membrane)
Genetics
Environmental insults
Cyclopia is caused by
Holoprosencephaly
Sirenomelia is caused by
Caudal dysgenesis
Sacrococcygeal tumors are associated with
The primitive streak (remnants)
The primitive node is often called “____”
The organizer
Splitting of the primitive node causes
Conjoined twins
What is the ampulla and what happens there?
The widened part of the distal uterine tube; where the sperm and the egg meet
What is the purpose of the fimbrae
Sweep up released oocyte into fallopian tubes
The myometrium is made of?
Where is it in relation to the endometrium
Smooth muscle
On the outside
When is an oocyte considered a zygote
During the two cell stage after fertilization; around 30 hours
When is a zygote considered a morula
16 cell stage and above
Explain the purpose of the trophoblast and what it eventually turns into during development?
Provides nutrition & support for the developing embryo
Eventually becomes the placenta
24 hours after being released, if an oocyte does not come into contact with sperm ….
It starts to degrade
Another name for inner cell mass
Embryoblast
When does the blastocyst shed the zona pellucida?
Prior to implantation
Around 41/2-5 days
Why is cervical implantation not ideal? Is the pregnancy viable?
Very inferior
Growth of the fetus in the narrow area would cause lots of pressure, not enough room to grow
HIGH RISK but viable
In normal implantation, the oocyte moves ______ towards the ____
Proximally, uterus
Where is the zygote implanted in a peritoneal pregnancy ?
How does this happen?
Is this viable?
Abdominal
The zygote moves distally and falls out of the fallopian tubes
No!
What type of cells on the blastocyst invade the uterine wall for implantation
Trophoblast cells
What is the difference between the syncytiotrophoblast and the cytotrophoblast cell populations? Be specific
The sync = ‘together with’ the endometrium
Multinucleated region because cells push into endometrium and lose cell walls
The cyto = stem cell population
Cell walls in tact
What releases hCG?
Syncytiotrophoblast
What cavity will eventually surround the developing embryo
Amnionic cavity
When a pregnant persons water breaks, what is the fluid that is actually being released?
Amnionic fluid
Why would it be beneficial to insert a needle into the Amnionic fluid during a pregnancy?
What can we do with the extracted liquid?
Extract cells that have sloughed off the developing embryo, allows us to understand how the development is progressing
Perform a karyotype and do genetic testing
Why would it be beneficial to insert a needle into the Amnionic fluid during a pregnancy?
Extract cells that have sloughed off the developing embryo, allows us to understand how the development is progressing
Why might a woman not know she is pregnant? Aka, why might a woman be spotting when she is actually pregnant,?
Trophoblastic lacunae (lakes of blood) may rupture and be released at certain points during early development
The mesoderm splits into two layers, what are they? Which is closer to the yolk sac?
Which is closer to the trophoblast cells? (Which ones)
What is the cavity that forms?
Splanchnic & somatic
Splanchnic
Somatic
Chorionic cavity
What does the Splanchnic mesoderm form
organs
**internal
What does the somatic mesoderm form
Body wall
*external
At the end of the 2nd month, has the yolk sac fully regressed?
NO
When is the yolk sac no longer present?
End of 3rd month
The primitive streak is formed on the
Epiblast surface
All cells technically develop from which layer
The epiblast
The first wave of cells that migrates to the primitive streak will replace the _____and turn into the ____
Hypoblast, endoderm
Cells migrate from the ____ towards the primitive streak
Epiblast
The second wave of cells migrating to the primitive streak develop into the
Mesoderm
The epiblast eventually turns into which layer
The ectoderm
A teratogen refers to
The agent responsible for birth defect
Sacrococcygeal tumors are located
On the lowest part of our spinal column
What structure fails to divide that causes cyclopia
Forebrain into right and left
What fails to divide that causes sirenomelia
Caudal end
The ___ membrane develops faster/sooner because …
Oropharyngeal , the cells migrate through primitive streak towards it
The body plan is decided by the
Primitive streak
Where does the gut tube develop from
The endoderm
The cytotrophoblast is the ___- for the ____trophoblast
Stem cell population, synctio
