Embryology (week 3, week 4-8, and abnormal development) Flashcards
What is the formation of the germ layer called
Gastrulation
Where is the primitive streak found
formed in the midline of the epiblast by the invagination of cells
When can the axis of the embryo be determined
by the formation of the primitive streak
The epiblast cells displace to between the hypoblast around day 15 and from what
a trilaminar disc - specialised germ layers
What is the three layers of the trilaminar disc
Endoderm
Mesoderm
Ectoderm
What is NEURULATION
neural tube formation
What is the formation of the notochord
Cells sink down from primitive streak in the ectoderm and sit below the mesoderm
What does the notochord induce and how?
The formation of the neural tube
sends signal up for the ectoderm to thicken forming a neural plate, the neural plate then sink down forming a neural tube
What induces the mesoderm to thicken
the neural tube
What three parts does the mesoderm separate into
in order of the closest to the neural tube to the furthest away
Paraxial mesoderm
Intermediate plate mesoderm
Lateral plate mesoderm
What does the paraxial mesoderm segment to from
somites
What does the intermediate plate mesoderm go on the develop
urogenetial system (reproductive and urinary)
The lateral plate mesoderm splits to from what
somatic mesoderm
splanchnic mesoderm
What does the lateral plate mesoderm go on to develop
The body cavities
The pleura
The peritoneum - forms the lining of the abdominal cavity
What is the space between the splanchnic and the somatic mesoderm in the later plate called
intraembryonic coelom
What is the 4th - 8th week of development called
Organogenetic period
What days does the heart start to beat
day 24
How many pairs of somities from from the paraxial mesoderm
43
Where does gut formation occur
the endoderm
During what period does limbs bud and the neck from
Organogenetic period
What further development happens to the neural tube during the Organogenetic period
forebrain, midbrain, hindbrain and spinal cord development
What surrounds the mesoderm
the ectoderm
The lateral plate mesoderms splits to from the splanchnic and somatic mesoderm what membranes do these form
Therefore what is the intraembryonic coelom space inbetween the membranes formed
Splanchnic - viscera pleura
somatic -parietal pleura
intraembryonic coelom - the pleural cavity
What do the somites divide further into 3 parts
Dermatome
Myotome
Sclerotome
What does the dermatome develop into
the dermis of the skin
what does the myotome develop into
the muscles of the body
what does the Sclerotome develop into
the bones and vertebra of the body
What cavity surround the entire embryo
the amniotic cavity
What initially provides nourishment while the placenta matures and is fully formed
the yolk sac
What surround the embryo in the amniotic sac
nutrients
What is Teratology
study of when things go wrong during development
what are environmental factors that cause abnormal development called
teratogens
What are the causes of abnormal development
Drugs tobacco radiation alcohol infectious agents
ALSO
Genetic factors - structural or numerical
increased mothers age
How do these factors affect foetus development
as transfer through the placenta from the mother to the foetus
What is the risk of teratogens depend on
The time of the exposure - e.g. critical development
the dosage of substance
the embryos susceptibility
What period week has the greatest risk of teratogens and why
weeks 3 - 8
period of greatest sensitivity as this the most crucial development point
what time period has low effect of teratogens but has the highest risk of death
week 1 - 2
how can malformations be diagnosed prenatal
Blood
ultrasound
amniocentesis
What is the main thing that happens week 4 in the development of the foetus
folding of the embryo
