Embryology Flashcards
When does gastrulation occur?
Third week of development, marking the start of the embryonic period
What is gastrulation
Bilaminar disc, epiblast and hypoblast Converted into a trilaminar disk Ectoderm, mesoderm, endoderm
How does gastrulation occur
Primitive streak forms in the epiblast, leading to migration and invagination of epiblast cells
Why does gastrulation occur
To ensure the correct placement and precursor tissue to allow subsequent morphogenesis to take place
How many weeks after fertilisation is the embryonic period
3 to 8
teratogenesis Effects which stage of development the most and why
Pre-embryonic - lethal effects
embryonic - the most sensitive - As this period where systems were developed
fetal - less sensitive - period about growth and function maturation of systems
What structure appears on epiblast layer during gastrulation
Primitive streak, with no laptop
What happens to hyperblast layer in the formation of trilaminar disc
Is displaced, does not form any of the three layers of the trilaminar disc
Name the three layers the epiblast differentiates into
Ectoderm
mesoderm
endoderm
Which two parts of the trilaminar disc which are not 3 layers
Future anus and future mouth
Ectoderm will feature develop
ecto= outside
Organs and structures that maintain contact with outside world
such as the nervous system and the epidermis
Mesoderm future develop
Supporting tissues, muscle cartilage and bone vascular systems including heart and vessels
Endoderm will future develop
Internal structures, epithelial lining of GI track, respiratory tract
Immotile cilia can result in
situs inverters
Howard left and right asymmetry produced
Ciliated cells at the node result in leftward flow of signal molecules. Site-specific signalling cascade initiated. Absence of signal results in right sidedness
Which layer does the notochord form in
Mesoderm
Notochord in neurulation leads to
Solid model cells running down the midline. Send signal to overlying ectoderm to differentiate into neur ectoderm.Electrical signal causes overlying ectoderm to thicken. Slip a shape neural plate Edges elevate out of the pain of the disc and card towards each other creating the neural tube
Name of first cavity inside embryo
Intra embryonic coelom
What do somites derived from
Pariaxial mesoderm
Total number somites
31
Somites broken down to form
Sclerotome - eventually form bone
Folding in the head to foot plane is called
cephalocaudal Folding
What is folding achieve
Draws together the margins of the disc
creating a ventricle body wall
pulling amniotic membrane around the disk
Embryo becomes suspended within the amniotic sac
pulling connected stalk ventrally
Fording allows everything to be put in my place
Three stages from fertilisation to birth
The embryonic 1-2 weeks
embryonic 3-8 weeks
fetal 9-38 weeks
These are weeks post fertilisation
Gestation age
Time since last menastration. Embryonic age +2 weeks
Three stages of pre-embryonic period
Cleavage
compaction
implantation
What is cleavage
Forms morula
What is Compaction
Forms blastocyst
Ideal location for fertilisation to occur
Anterior posterior ampulla of fallopian tube
What you call a fertilised oocyte
Zygote
Explain cleavage
Cleavage forms morula series of mitotic divisions begins 30 hours after fertilisation results into blastomeres of equal size zone of lucida glycoprotein shell ensures only one sperm fertilised egg
During cleavage the cells can be described as
totipotent - Has the capacity to become any cell type
What embryonic stage can create implantation genetic diagnosis account
morula In cleavage
Explain compaction
Formation of first cavity
full blastocyst
inner cell mass - embryoblast
Outer cell mass - Trophoblast
Cells in compaction can be described as
Pluripotent the capacity to become one of many cell types
What needs to occur before implantation can occur
Hatching, blastocyst hatches from zone pullucida
can now interact with uterine surface to implement
How many cells does the conceptus have during implantation
Hundred, eight in Embryoblast and 92 trophoblast
What happens in the week twos
Two distinct sailors emerge from
the outer cell mass trophoblast
x syncytiotrophoblast
x cytotrophoblast
inner cell mass embryoblast becomes bilaminar disk
x Epiblast
x Hypoblast
Bilaminar disc
Epiblast and hypoblast
What region of the uterus does implantation occur
Implantation is interstitial, uterine epithelium is breached and the conceptus implants within the uterine stroma
Why does implantation occur
To establish maternal blood flow in the centre
Basic structural units of materno-fetal exchange
Chorionic illness
Conditions linked implantation defects
Ectopic pregnancies
centre Praevia
abembryonic pole
Primitive yolk sac formed
Embryonic pole
Rapid development of syncytitrophoblast
which later is the yolk sac membrane in contact with
cytotrophoblast
Primitive yolk sac membrane is pushed away from cytotrophoblast by
And a acelluar extra embryonic reticulm
Which layer interacts with the maternal blood vessels
syncytiotrophoblast - Indeed maternal sinusoids
What is the secondary yolk sack made from
The primitive yolk sac
What Suspends embryo
Connecting Stalk
What is the amniotic sac formed from
From from spaces within the epic last
