Comprehensive Guide to Human Blastocyst Implantation Process

hello students today we will discuss about the implantation

my dear students whenever you are talking about the changes going in the first week of fertilization

you have the cleavage and after the cleavage there is a formation of the blastocyst now when we are talking about

the blastocyst this is the stage which is also covered by Zona pellucida so when the implantation will take place

the first prerequisite is that there has to be the removal of Zona pellucida so as soon as the Zona pollution disappears

the process of implantation starts so lets ah discuss what is the definition of implantation

so my dear students in the implantation what is happening that this is your uterine cavity and in the uterine cavity

this is the wall of uterus which is known as endometrium now in this endometrium this blastocyst is going to

implant now there is a two process will take place one is known as

addition of this blastocyst with the endometrial wall and later on it will penetrate the whole thickness of this

endometrium till the functional layer as you should know that the endometrium is having the two part functional layer and

the basal layer now when we are talking about this implantation the implantation will take

place in the functional layer that is its two layers stratum compactam and spongiosum

so the in implantation when you are defining the implantation it is defined as a

penetration this word has to be there penetration of the decidua now what is decidua decidua

means your two layers stratum compactam and stratum spongiosum of endometrium so

implantation is penetration of the decidua or the functional layer of endometrium by blastocyst

and later on this blastocyst completely invade completely invade the thickness of the

decidua that means at the end of the implantation you are not able to see the developing zygote or the embryo into the

cavity the uterine cavity is completely empty what does it mean that initially if you

will see this is your cavity and inside the cavity you are able to see there is a

blastocyst but this blastocyst will disappear inside the wall of the endometrium and at one end you will find

there is no developing blastocyst or the embryo so this is what is about the definition that definition will have the

two word one is the penetration and second is the penetration is followed by the complete invasion of the endometrial

wall by a blastosis clear now the second thing comes is what is the duration so my dear students the implantation

will start after The Disappearance of the zone of elucida and the implantation is done by the blastocyst stage so we

know that the modula will form on the third day and on the fourth day the blastocyst will form and once the

blastocyst will enter into the uterine cavities is still surrounded by the Zona pelucida so The Disappearance will start

from the sixth day so the implantation will start from the sixth day that means the implantation is a feature of the

first week of but it will not complete in the first week it will complete into the second week on the 12th day or the

13th day of fertilization that means if you will open the book you will find that

fertilization is a feature of both first week as well as second week because the process starts at the end of first week

but it complete on the 12th day or 13th day after fertilization in the second week

now what is the site of implantation now when you will see the pelvis now this is your anteriorly

placed pubic symphysis this is your sacrum now in the female pelvis here you will have the urinary bladder

posteriorly will have the rectum and in between you will have this uterine cavity this is your cervical canal

now here you can see that this uterine cavity is having the anterior wall and it is having the posterior wall

so when we are talking about the implantation site the most of this time the blastocyst implant on the posterior

wall in more than 50 percent cases in remaining cases the implantation occurs

on the anterior wall but it should be in the upper part of the body of uterus

so what is the site of implantation the site of implantation occurs in the upper part of the body of uterus on posterior

wall it can occur in the anterior wall but it should not be in the lower part so the upper part of the body of uterus

is a normal side of implantation which can be on the positive oil in more than 50

cases and or it can be in the anti-wall in remaining cases clear so what are the type of implantation in

human answer is interstitial now what do you mean by interstitial type interstitial means that this is

your cavity of uterus and when there is a formation of the blastocyst this blastocyst ultimately disappear from the

cavity and it completely invade inside the wall so interstitial means when the

blastocyst completely enter into the wall of the endometrium this is known as interstitial type clear

then what is the process of implantation so my dear students there are two process

now one process is necessary for the endometrium that is known as decidual reaction

so this decidual reaction is a process which is taking place into the endometrium

the remaining part is a process of your blastocyst and this process of blastocyst is responsible for the

implantation so let's discuss about the first process decidual reaction

so let us discuss the decidual reaction first now what will happen in the decidual reaction decidual reaction take

place into the endometrium second thing is that in the decidual reaction

this is our decidua you will know that there are three layers in the uterus inner side is known as endometrium then

this is the second layer is known as myometrium and the outer's most is perimetric

now this endometrium is further having the three layer this is your spongiosum then you will have the

compactam and this is the basal layer now these stratum spongiosum and compactum are known as functional layer

of endometrium now in this functional layer what is happening

the cells of the stroma or you can this say the cells of the endometrium enlarges

now this enlargement occurs because of the increase in the glycogen material

increase in the lipid material increase in the fluid material so the cells will enlarge into the size and there is a one

very important thing is that when the implantation is taking place your endometrial is already under the

secretory phase so in the secretory phase when the implantation is taking place in the

endometrium the cells are changing themselves and that change is known as residual

reaction and what is the changes are taking place that the cells will swollen up they increase in the size they are

getting more and more glycogen more and more lipid more and more fluid why so that they can provide nutrition to the

coming blastocyst or the developing embryo here so this is the one change which is taking place here into the

endometrium during the process of implantation now these changes are taking place into the blastocyst so what

is the first change now I told you that this is the zone of elucida and inside the zone of elucida this is your

blastocyst which is lined by the trophoblastic cell and inside one end you will have

embryoblast and this cavity is there which is known as blastocele killer now this Zona palacida avoid the

abnormal implantation so first what will happen there is a disappearance of the Zona palacida which is known as hatching

so what is the first step in the implantation at the blastocyst answer is hatching of the blastocyst that means

disappearance of layer so now this is The Disappearance of your

zonopallocida now the second layer is addition of blastosis to the endometrium now

this part will take place from which end of the blastocyst this is the question of your exam that which part of the

blastocyst first show the addition to the endometrium or maternal epithelium answer is

polar trophoblast or you can say the embryonic Pole so this embryonic Pole or the polar and

side of the trophoblast first will go and attach with the uterine epithelium or endometrium so what will happen here

that you know that this is your maternal side so this is suppose this is your endometrium

so this polar trophoblast first go and just show the addition

and this addition will stimulate further changes now this addition is known as partial or

superficial implantation which is taking place on the seventh day now when you will move into the second

week of the development this partial implantation completes into the deep implantation

so this addition is important now as soon as the addition will take place there is a splitting of the

trophoblast into the two layer now what will happen here in the next stage so in the next stage you will find

that the polar trophoblast shows the splitting so now what will happen in the next stage now this is our prophoblast

on the Polar side and now there is a formation of one more layer which is known as Synthesia layer

since issue trophoblast now these since isiotrophoblast cells releases the proteolytic enzymes and

these proteolytic enzymes start to replace more and more endometrial cells so that this blastocyst

invade what it invade it invade the decidua so these Sensational layers is

responsible for the penetration of the blastocyst through the uterine endometrium which is known as deep

implantation so what is happening first disappearance of Zona palacida then the polar

trophoblast shows the addition with the maternal endometrium

now this is known as partial implantation on the seventh day now because of this there is a splitting

occurs in the polar trophoblast first and there is a formation of sensation trophoblast these sensitio trophoblasts

have the capability of deep penetration so they will release the enzymes and these enzymes will displace the

endometrial wall cells or the decidual cells so that slowly this blastocyst will go deep and deep into the maternal

endometrium clear so what will happen that ultimately you will find that this will disappear from

the uterine cavity and there is a formation of a small puncture here

into the endometrial wall and through this puncture your blastocyst will enter and it appears inside the decidua and it

is covered by the synial layer now this Gap or the puncture into the endometrium through which the blastocyst enters

inside the wall of the endometrium later on filled by a coagulum and this coagulum is formed by the fibrin

material so this is known as fibrin coagulum and later on this coagulum is further

replaced or healed by uterine epithelium clear so what are the steps in the implantation first hatching second

addition of the blastosis to the endometrium third addition is followed by the Deep implantation that is the

penetration of the blastocyst now there is a differentiation occurs along with this penetration at the polar

trophoblast and that's why the Sensational layer is responsible for the penetration and lastly there is a defect

of the endometrium is healed so there is a one more change occurs in this Sensation that there is a formation of

the primary Villi with the lacunes and these lacunes are later on filled with the maternal blood that we will discuss

in the coming part of the our discussion of embryology classes so my dear students

what is the applied aspect so you can write down abnormal implantation in two way

one the implantation occurs abnormally inside the uterine cavity and one the abnormal implantation occurs

outside the cavity now in the uterine cavity if abnormal implantation occurs in the lower part

then it can lead to a condition is known as placenta previa

if implantation occurs outside the uterine cavity it can go in the ovary it can go into the fallopian tube it can

go into the mesentery in the abdomen or sometimes it can go into the pouches that is pouch of Douglas

so these are implantations are known as ectopic pregnancy clear ectopic pregnancy in which the

most common type is fallopian tube pregnancies so how to write in the exam the steps of

the implantation first hatching of blastocyst that means disappearance of the Zona pellucida second you have to

write down the addition of the Polar end or the trophoblast with the uterine endometrium which is defined as a

superficial or the partial implantation followed by the penetration and erosion of the decidua by the Synthesia

trophoblastic layer which is known as deep implantation and then what is happening there is a

formation of the lacunar spaces Into The Sensational layer and those will those will fill with the maternal blood and

simultaneously the penetrating area or the defect which has been created by the invading blastocyst is closed with the

help of fibrin plug which later on healed or covered by the endometrial lining killer you can draw this diagram

also in the exam which is showing that how this endometrial wall first is having a defect and through this defect

this blastosis is going deep and deep now these are the polar trophoblasts which has already been differentiated

into a multi-nucleated layer is the synthesiotrophoblast and these Institute trophoblasts are responsible for the

Deep invasion of this developing embryo clear so now at the end of this session of the implantation you are you are

having a idea what are the steps of implantation how to write in exam and what is the

important things to write down in each and every point so this is all for the session thank you