Gastrulation, the critical process of transforming a bilaminar embryonic disc into a trilaminar disc, is highly sensitive to abnormalities, particularly teratogenic exposures, which can lead to severe developmental defects affecting midline structures, caudal development, and organ asymmetry.
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in the last lecture we were talking
about the process of gastrulation
in embryology what is meant by gastrolation
gastrolation
gastrulation is the process by which the
bi-laminar disc convert into
trilominar disc is that right that is
what we discussed in the last lecture
today we will talk about the problems or
abnormalities which may occur during
gastrulation one point I would like to
highlight sometimes in mcqs they try to
put a very funny
distraction to you they give a choice
that gastrulation mean formation of stomach
stomach
and many students take it right that is wrong
wrong
because in student mind gastro means
something related with the stomach and
when they give the process of
gastrulation during embryogenesis means
formation of stomach so don't say oh
this is the easiest answer he says it is
right this is wrong
in the embryogenesis process of
gastrulation is not the formation of
stomach or formation of gastrointestinal system
system
during embryogenesis right during the
embryological development
gastrulation means the process by which
biliminal disc convert into
trileminar disc you remember biliminal
disc is seen in which week
this is developed in which week of development
development right
right
yes biliminal disc is formed during
in the second week what do you think
second week yes
second week that's very easy biliminal
disc bimin two lamina and second wave
and triliminal disc Prime in three three
lamina in third week is that right
now we will talk about that what are the
possible or different type of
abnormalities which may occur during the
process of gastrulation one of the very
important abnormality is related with
the alcohol intake by the mother right
what are the abnormalities termed the
abnormalities which develop during the
early embryological development those
abnormalities are called
for example alcohol damages the gerund
disc or female take some drug and that
damages that embryo right so
damage to embryo during its early
development is called terrato
terrato
teratogenesis what is that called parato
parato Genesis
Genesis
right during what we are studying during
gastrulation gastro lation
lation
teratogenesis during gastrulation and
those substances which produce
teratogenesis those substances are
called teratogenic substances
you will study in Pharmacology there are
many drugs which are teratogenic there
are many toxins which are teratogenic
right now we will talk about alcohol
that alcohol intake
high dose of alcohol
big amount of alcohol
intake at the time of development of
trilaminar disc damages the developing
embryonic tissue
right and how it damages
before really I tell you you know third
I told you that gastrumulation start at
the end of the third at the beginning of
the third week right let's put the
female reproductive cycle here okay
okay
let's put a different color this is
female reproductive cycle let's suppose
this female has 28 days
cycle in 28 days cycle this is a
bleeding for first four or five days is
that right
and after that when is the time of
ovulation suppose this is the 28 day cycle
cycle
so when is the ovulation time
14 days right most probably that around
the 14th day of the cycle she ovulated
and if she was producing oven at that
time and she had intercost around that
time there are chances that her ovum
gets fertilized so it means if ovum gets
fertilized look at this over I'm very
happy because it became fertilized right now
now
already you know that from 14 days and
21 day and then
28th day when this over and will of
course go into two cell stage right then
it will go into four cell stage then it
will go into morula then it will go into
blastocyst you know what all that thing
and then it will go into bilaminar
bilaminar
what is this by laminar disc and around
this time this bilaminar disc will start
converting into yes please
try laminar
desk right it is precoordal plate and
here is primitive streak and here is
Noto chord this is what we discussed
last time so this process has started at
the beginning of the
at the beginning of the third week
this is the first week of development
this is the yes
second week of development and this is
the beginning of the
third week of the development
now listen very carefully and all your
life and you're doing Medical Practice
you have to take care of this fact
female is expecting that she will have
next menstrual bleeding around these days
is that right
She is expecting to have her periods
around these days
and actually because she is pregnant right
right
of course she will miss these periods
and around this time embryonic tissue is in
in
converting bilometer into
dry lemonade disc or we say the process
of gastrulation is going on now
around this time she may think that her
periods are somewhat delayed and very
soon shortly they will start and she may
not be aware that she is pregnant
am I clear
there's if this female is
not aware that she is pregnant and even
though her Menses are periods did not
start in time but she may think they are
little bit delayed and she may not take
those special precautions which usually
she will take if she knows she is pregnant
pregnant
is that right because she is not aware
that she is pregnant so if she is a
woman who takes alcohol she may take a
large quantity of alcohol
and that may damage
the developing trilominal disk
is that right now
now
in trilominal disc around this time
most of the cells are pre-programmed
that which tissue they will be making
when the trilominar disc is being formed
ectodermal mesodermal and endodermal
cells are already pre-programmed that
what tissues will be made out of
ectoderm what tissues will be made out of
of
mesoderm and what what which tissues
will be made out of
endoderm is that right so this is a very
very sensitive time from here onward
this is the beginning of third week from
third week of castration up to the
eighth week of gestation it's the most
this is the most dangerous time to lay
during the development of the embryo
why because during this time
three layers ectoderm mesoderm and
endoderm will form and then
they will start giving rise to the
tissues and organ system
and up to the eighth week of up to the
eighth week most of the body tissues and
organs are made
they're well established after this
further development is usually maturity
of the organ system the formation of
organ system is done again listen
carefully formation of organ system like
central nervous system or respiratory
system or cardiovascular system or
gastrointestinal system or endocrine
system so most of our body tissues
almost all of our body tissues and organ
systems have started forming from the
trilominate disc during this time and
most of the tissues are
basically formed by the
eighth week of gas station
after that organ system simply become
larger and mature
is that right now why I am stressing so
much on this because if during this
mother take some substance
right which is teratogenic substance
which is toxic to the developing
embryonal cells a little damage to
embryo May produce a very big damage to
the developing system
for example
here there's a very small area which is
going to make central nervous system
and here
and if alcohol damages that area
when baby will be bombed you will find
there's a big damage to central nervous system
system
is that right
so this is the most vulnerable
time most vulnerable window time window
through which the damage is done to the
developing embryo you may be thinking
I'm repeating I tell you it's worth
repeating again and again again and
again right with the females who are in
relationship and if they are there is a
chance that they may become pregnant
right and if they become pregnant around
this time they have to be very very
careful what type of substances they
ingest what types of drugs they are
putting in their body am I right now
let's come to exactly situation here the
female trilamina disc Plus
what is this
alcohol and what happens right
right
this is crocoder plate here is your yes
primitive streak and
here was your yes please what is it ectoderm
ectoderm
measure them very good and just last
lecture we discussed the lower most area
will be yes
and you should not forget we put a lot
of time to understand what was here notochord
notochord
right this is present between the
actor domain
Androderm and
pressed between the ectoderm and
androdum and on the sides of it it has
mesoderm now
this is a diagram you should not forget
I should make alcohol is a dangerous
thing now
this is the mother she is taking alcohol
alcohol is lipid soluble or not lipid soluble
soluble
alcohol is lipid soluble or not lipid
soluble it is a highly lipid soluble so
when she will take alcohol it will
rapidly absorb from git
go into her blood and any substance
which is a highly lipid soluble will
efficiently cross placenta any substance
any drugs or any substance which is
highly lipid soluble will dissolve into
placental barrier and go to the placenta
and baby
is highly lipid soluble so it will be
going to the product of conception here
I will not use the word placenta because
so at so early stage placenta is not
developed so I will say that alcohol
from maternal blood will
dissolve into biological barriers
and cross and reach up to the product of
conception and now look here these are
the drops of alcohol
going to destroy yes
these cells which are in the middle part right
right
these are midline cells midline
cellular structure from pre-codile plate
and anteriorly it may be destroyed
they are very very sensitive to the
higher doses of alcohol and if this area
is destroyed then all the structures
which will develop out of this area they
will be abnormal
now when the baby develop what really
happens that this area right Plus
here is also damaged by this
now what really happens all these
midline structures
which are damaged by alcohol
right will affect the baby development
and when this baby will develop look
here these structures are in abnava
because you know this was the disc you
are damaging this area of the disk when
baby developed this part of the disc
fold and this becomes the front of the
head and neck
so this frontal area is also damaged
for example the eyes of the baby
and Central structures
they are underdeveloped if Central
structures midline structures are
underdeveloped eyes will become near or
they will become far
they will become near if these Central
structures are not formed or they are
under formed then eyes will become more
near right for example normally
I should be something like this right
right this is the abnormal baby
you understand what has happened
mid lane structures are these structures
are absent so eyes become very near to
each other
for this
problem we use the term that there is hypo
hypo
telomen telescope
hyper mean if in any disease eyes go
away from each other we say hyper
terrorism in this problem I will come
very near to each other we call them
hypothelorism what is it called
hypotenourism plus do you think this
part of the central nervous system the
forebrain it will dwell up well
no so there will be under development of forebrain
