Embryology (early development) Flashcards
what 4 main functions do cells show
proliferation
movement (chemotaxis) differentiation
loss (apoptosis)
how do embryonic cells functon diffferently to omatic cells
mature cells normally show one characteristic at a time-
In an embryo, cells may show the proliferate, move and differentiate simultaneously
simultaneously.
how does regulator factor expression produce different outcomes
Gradients/ combinations of regulatory factors;
Spatial/ temporal changes in these factors, or in the responses to them.
Embryonic development is usually considered to start with….
fertilisation which leads
immediately into preimplantation development (PID) of the conceptus.
wher and over what time period does PID occur
within the fallopian tube over a period of 6 days,
what is PID characterised by
characterised by a series of cleavage
divisions that results in the formation of the morula (a ball of undifferentiated cells).
what does the morula form
develops into a blastocyst-
what are the key features of the blastocyt
has an outer layer of trophectoderm
an inner cell mass
and a fluid filled cavity.
when does the blastocyt implant into the uterine lining and hwa happens when it does
(by 10 days post-fertilization)
inner cell mass
becomes a bilayer disk.
what does the bilayer disk gve rise to
all of the tissues of the human fetus by
a series of complex changes…
what is the bilayer dsk composed of
hypoblast and epiblast cells
what are the complex changes which the bilayer disk undergoes
Gastrulation and Neurolation
describe the process of gastrulation
convertes bilayer disk to trilaminar embryo, containing the three layers of germ cells.
(precursors to all tisues in the body)
when does gastrultion occur
14-18 post-
fertilisation.
does neurulation start after astrulation
NO
Neurulation is initiated before gastrulation is complete.
describe the process of neurulation, what controls it
differentiation of
the ectoderm to generate the CNS,
under the control of the notochord in the
mesoderm
how does the neural plate form a sealed tube
develops two folds which
increase in size until they meet over the neural groove and fuse to form the neural
tube.
when does fusion of the 2 neual tubes occur
Fusion occurs during week 4 of development as the CNs becomes a sealed
tube.
what is occuring in parallel with neurulation
precursors of other tissues are developing within the
embryo, and it is being converted from a flattened structure into a 3D embryo.
during the third week of development whcih strcire outside the embryo are also developing
the primordial germ cells
cardiac/ vascular progenitors
in which direcions does folding of the emryo occur
both laterally and in the anterio-posterior direction
what can be said of the embrto by the end of week 4
precursors of all internal tissues have been laid down
many external structures are also developing.
sumarise the events of week 3
Formation of trilaminar disc (mesoderm),
CNS & somites.
Blood vessel initiation. Initiation of placental villi. (3mm).
summarise the events of week 4
Closure of neural tube. Heart, Face, arm initiated.
Umbilical cord. Elaboration of placental villi. (4mm)
define conceptus
everything that is produced from the fertilised egg.
define embryo
whole product of conception, includes cells that give rise to the baby
and everything else that results from conception such as the placenta and umbilical cord.
when does embryonic development cease
after 8 weeks post-fertilisation as the conceptus
is nor clearly human and classified as a fetus.
what are the 3 layers of the trilaminar embryo which gastrulation forms
ectoderm
mesoderm
endoderm
what does the ectoderm give rise to
skin, nervous system
what does the mesodem give rise to
skeleton, muscle, kidney, heart, blood
what does the endoderm give rise to
gut, liver, lungs
what does the grrove above the neural plate act as
negative regulator to
prevent proliferation occurring at the groove.
In the second month what is happening
limbs, face and internal tissues (heart, lungs, gut) develop
looks human by day 56
how does fusion of the neural folds occur
fusion point moves anteriorly and
posteriorly with neuropores at each end.
how does brain develop
Fusion of tissues and elaborations results in brain
developments. The two halves of the brain form separately and then join.
