Comprehensive Guide to Fertilization: Process, Steps, and Effects

hello students in today's lecture I will talk you about fertilization now whenever we will talk about the

development in the first week of the life what will happen as soon as there is a ejaculation occurs the sperm is

going to meet with the secondary oocyte and we know that the secondary side and sperm meet into the ampullary part of

the fallopian tube and that process is known as fertilization so in the first seven days there are

three things which is always there and you have the questions on them the first is fertilization

second is known as cleavage now cleavage is a process of mitostic activities and the third and the last

step is implantation that means when there is a first seven day life if you are talking about from the fertilization

the fertilization is on the first day and the first week end with the implantation in the uterine cavity so

let's discuss about the fertilization how to write in your University exam so my dear students the always we

require two gametes for the fertilization female gamete which is in the form of secondary site and we need a

male gamete that is known as spermatozoa now these both gametes meet into the fallopian tube and before meeting you

need the priming of these two gametes so when we are talking about the fertilization the first thing comes is

definition of fertilization so the definition of fertilization means when there is a Fusion of

male and female gametes and these gametes when they will fuse you are having a product and that

product is known as zygote and here if you will see you will realize that the sperm and the oocyte

both are haploid in nature and when we are talking about the zygote it is deployed in nature so what is the

definition of the fertilization fertilization is a process of the fusion of the male and female gamete to form a

zygote and by the process of fertilization the two haploid cells fuses to form a diploid cell clear

so where the fertilization take place fertilization take place in the amp law of Fallopian tube

so as I told you the there is a prerequisite is always there for the male gamut to become or to achieve the

capability to fertilize a ovum what does it mean that suppose if you are having a collection of the freshly

ejaculated semen outside the female body what I am saying outside the female body if you are collecting the some C1 into a

vessel now the sperms which are present into this semen are right now not having the capability to fertilize the over why

because these sperm has to go under the priming the process is known as priming and that priming can be take place by

two ways either you will place these spermatozoa inside the female genital tract

or you may do artificially inside the lab with the help of some enzymes so my dear students these spermatozoas

has to go under some priming and that priming is the prerequisite and after that the spermatozoa will get or will

achieve the capability to fertilize the over so what is that prerequisite the first process is known as capacitation

what is that capacitation now in the capacitation we are doing a process that is known as

conditioning that is known as conditioning of your spermatozoa and the conditioning is also

known as maturation of spermatozoa so by the conditioning or maturation of spermatozoa the

spermatozoir is going to achieve the ability to fertilize now C for capacitation c for

conditioning and this conditioning will take place in the female genital tract when there is a contact of the sperm

with the female mucosa and female mucosa produces some enzymes and those enzymes will change the

property of the head of the sperm and what are these two things those will change there are two things which change

that is known as the conditioning first thing is known as there is a removal of glycoprotein code

there is a removal of glycoprotein code from the head of the sperm and second thing is there is a removal of

semen plasma protein

so these two things has to remove from the head of the sperm to make or to allow or to mature the spermatozoa so my

dear students whenever you are reading or whenever you are writing the Fertilization in your exam this is my

sincere suggestion that always write the capacitation in the bold letters because it is a very important prerequisite

which causes priming or maturation of the spermatozoa and it is defined as a c for capacitation c for conditioning so

capacitation defined as a conditioning of the spermatozoa and in this process when the spermatozo are passing through

the female genital tract and there is a contact of female mucosa the female mucosa releases the enzymes which will

remove the glycoprotein code and the saminal plasma proteins from the head of the sperm clear so this is the first

process which is known as capacitation now there is a second prerequisite is known as

acrosomal reaction acrosomal reaction now what is the acrosomal reaction now acrosomal

reaction means that the head of the sperm start to release the enzymes now what

these enzymes these are hyaluronidase and acrosine

these enzymes released from the head of sperm once they will contact the secondary oocyte so my dear students

these two things capacitation and

the acrosomal reaction are compulsory or you can say the prerequisite for a spermatozoa to

penetrate the different barriers of secondary oocyte and to fertilize it clear so when we are starting the

writing in exam first we will Define the fertilization then we will Define the process of priming where you have to

detailed about the capacitation and acrosomal reaction now we'll move to the steps of

fertilization so my dear students what will happen that when we are talking about

the female genital tract now suppose this is your female genital tract here is our

fallopian tube now the spermatozoa is entering till the sampula now in this ampulla what will happen the secondary

oocyte which has been released from the ovary by ovulation also

Approach at this point now in this temporary reason both the male and female gametes meet

so for the fertilization what will happen this male gamete pierces the barriers of the female gamete so what

are the barriers has been pierced by the male gamut so for that you should have an idea about the structure of secondary

oocyte so when you will see the secondary site there is a outermost layer and this

outermost layer is known as Corona radiator where you will have two or three layer of the cells and these are

known as Corona radiator cells clear now inside the corona radiator you will have a very important layer which

is known as Zona pallucida what is that Zona palusida so this is your Zona palusida

now inside the Zona pellucida you will have a third layer which is known as vitiline membrane

what is that vitiline membrane vitiline membrane is a another name of the plasma membrane of secondary oocyte

so from outside to inside when you are seeing the secondary side you will find the three layer this is the outermost

layer which is known as Corona radiator then this is Zona palucida and this is vitiline membrane

and this is your cytoplasm of oocyte which is known as o plus and inside the soup lab you will have the nuclear

material of the female gamete so my dear students what will happen when the

spermatozoa will approach the secondary suicide it will first Pierces this layer so the what is the first step

of fertilization penetration of Corona radiator then it will pierce this layer that is the second step that means

penetration of Zona pallucida then there is a third step penetration of vetteline membrane then there is a fourth step

Fusion of male and female nuclear material clear so when you are writing the steps of the fertilization you have

the idea of the three layers of the secondary side Corona radiator Zona palusida and vitiline membrane so

suppose if I am writing it in exam so what I will start there are four steps one

penetration of outer layer that is Corona radiator second penetration of Zona palucida

third penetration of vitiline membrane and the fourth step is Fusion of male and female

nuclear material so these are the four steps of fertilization

so once you will go through the force these four steps which I am not detailing here I am just explaining how

to write an exam there is a one very important thing occurs that as soon as our male gamut contacts with the

Corona radiator the acrosomal reaction starts what starts aggrosomal reaction and with the help of this acrosomal

reaction it releases the enzymes and those enzymes will start to penetrate these three layers clear so if acrosomal

reaction will not happen the spermatozoa will not able to pierce any of these three layer so these three layer

penetration is possible just because of the acrosomal reaction which occurs at the head of your spermatozoa

so now what will happen now what is happening here as soon as you will see that this is

your vitiline membrane after piercing the two layer that means your this a sperm as

pierces already the two layer this is your Corona radiator this is our Zona

palusida and now the sperm has pierced the third layer that is bitterline membrane

now once the head of the sperm come in contact with the vitiline membrane what will happen that this plasma membrane of

your had fuses with the vitiline membrane the plasma membrane of the head fuses

with this vitiline membrane of oocyte and this membrane on the interior surface of the head of the spermatozoa

already disappears while it is going deep and deep so we will remove this from here so if you will remove this

what will happen now this is in contact now here you will have the female nuclear material here we will

have the male nuclear material in the head you know the head contain the nucleus which is covered by the

acrosomal cap so once you will approach here what is happening that the posterior plasma membrane of the head

now fused with this vitiline membrane now interior surface ah acrosomal cap as well as the plasma membrane has already

been disappeared now what will happen as soon as this process of the fusion of plasma membrane

take place and male materials start to go in the female cytoplasm it produces a kind of

calcium wave and what is the effect of calcium wave now there are formation of granules and

this calcium wave shift these granules in the outer side and now they are known as cortical granules

now these cortical granules contains some enzymes these enzymes will change the property of vitiline membrane and

they will harden the vitiline membrane so what is the first effect of calcium wave calcium wave first produces or

shift the granules of cytoplasm towards the cortex and these granules releases the enzymes and

these enzymes changes the property of vitiline membrane as well as Zona pellucida so that is known as vitiline

depolarization and it is also no and it is known as Zona reaction

so what are the two things happening here what is happening as soon as the plasma

membrane of the male gamete fuses with the vitiline membrane there is a production of calcium wave

and this calcium wave is having multiple effects one of the effect is that the granules which are present in the

cytoplasm now shifted to the periphery now they are known as cortical granule and these cortical granule secretes some

enzymes these enzymes will change the property of vitiline membrane as well as the Zona palusida this is known as

vitiline depolarization and Zona reaction so by these two process

the property of fetaline membrane and Zona palacida has been changed so they are now become impermeable

they are now become mpermeable for other sperms and it avoid polyspermy

it avoids polyspermy so this is the one impact of the calcium wave what is the second effect of the calcium

wave the second effect of the calcium wave is that you know there is a presence of a nuclear material in the

female which is still in the arrest of second mutic division so this nuclear material completes its

second mutic division and it will form a pure haploid nuclear material and one polar body and this polar body will go

in the perivaterline space so the calcium wave is first creating a kind of

granules and these granules are responsible to avoid the polyspermy by changing the property of vitiline

membrane and Zona pellucida second this calcium wave is responsible to complete the second mutic division of this oocyte

nuclear material and it will produce a definitive haploid secondary site and this definitive haploid number of the

nuclei now going to merge with this pronucleus or the male nuclear material the third effect is that as we know

after the formation of the zygote there is a very high speeding divisions or the cleavage is going to take place so for

that there is a metabolic activation occurs clear so there are three things in your exam what are the

effects of calcium wave so the first effect is that it produces the cortical granules and these cortical granules

prevent the polyspermy by changing the property of vitiline membrane and Zona pellucida

second effect is that it is able to initiate the arrested second miotic division of female nuclei to complete

the division and so that you will receive a pure haploid definitive site and the third effect is that this

calcium wave is responsible for metabolic activation of your o plus clear

now the next comes is after fertilization what are the results of fertilization

so my dear students when you are talking about the results of first fertilization the first result is that it is

responsible to regain the normal diploid number of the chromosome because the two haploid cells are joining each other to

form a deployed cell so the number of that species regain second

there is a determination of the sex at the level of chromosome how

if 22x of the female fuse with the 22x of the male then you

will have the female child but if this egg will join with the 22 y of the sperm then you will have a male child

third the fertilization process of the fertilization there is a completion of

the second mutic division of your suicide which has been arrested for a long

and the fourth effect is that there is a metabolic activation occurs in the U Plus

which is which make this oocyte ready for the cleavage clear so these are the four effects of the fertilization but my

dear students there is a one very important term and that is known as Fusion of the nuclei which is a fourth

step now when we are talking about the fusion of the nuclei

there is a word come is pro nucleus male and female pronucleus now what is this pronucleus

now what will happen once the male nuclear material start to enter into the female cytoplasm it will show the some

kind of swollen and this swollen male nuclear material is known as pronucleus

now what is female pronucleus female pronucleus is formed after completion of second miotic division where you will

have a definitive haploid number of the cells so male Pro nucleus is a swollen nucleus

and female pronucleus form after the second meutic division and once the second mutic division occurs you will

have haploid number of the nucleus chromosomes in the nuclear material of the female in ooplas which is labeled as

a pro nucleus of female then my dear students there is a very important concept what will happen

in the U plus when the haploid number of the male and haploid number of the female

pronucleus join each other there is a process is known as DNA replication occurs

now this DNA replication is a compulsory step otherwise what will happen if without

replication this is having 23 chromosome this is having 23 chromosome and when these 23 23 chromosome arrange

themselves in a center along with the spindles and when there are splitting occurs what will happen

this is having a cell of 46 and this when the vertical is splitting without duplication occurs again the cells will

have 23 23. so this duplication or the DNA replication avoid this thing so whenever there is a DNA replication

occurs after the mitosis the cells always will have 46 46 if this replication will not occur as soon as

the pro nuclei are going to mix with each other as soon as the male and female nuclear material and chromosomes

align themselves on the spindles there has to be a DNA upper application so when there is a splitting of nuclear

material is taking place initially at the first part of the division there has to be the 46 46 chromosome in both the

cells which are deriving by the first cleavage so now how to write down in the exam first you

have to write down about the definition then what is the site of implantation these are the two steps of the priming

capacitation and acrosomal reaction then there are four steps of the fertilization that means penetration of

Corona radiator Zona palucida vitiline membrane and then Fusion of the pronuclei then what is the effect of the

calcium wave so calcium wave is producing three effect first is the change in the property of your zone of

elucida and vitiline membrane then the calcium wave is also responsible to complete the second mutic division and

the last effect is metabolic action what are the effects of fertilization and lastly a flowchart now how to make a

flow chart that you can see here how to make a flowchart in this flowchart I have started the flowchart from the

entry of your semen into the female genital tract so once you will have the deposition of

the spermatozoa inside the female genital tract there is a reaction occurs so the next step is the uterine

contraction start because of the release of oxytocin and this uterine contraction aspirate the male gametes inside the

uterine cavity and there is a capacitation occurs that means the conditioning of the spermatozoa will

undergoes and once the capacitation is taking place now the sperm is also having the property of acrosomal

reaction so now it will reach to the impula of your fallopian tube as soon as where you will have the initiation of

acronymal reaction and this acrosomal reaction helpful to penetrate all the three barriers and after piercing the

three barriers what will happen the head of the sperm plasma membrane merge or fuse with the vitiline membrane and it

will stimulate the calcium wave and the calcium wave will change the property of your vitiline membrane as well as Zona

pellucida to avoid the polyspermy and then there is a fusion of the male and female pronuclei and you will have a

formation of diploid zygote clear so my dear students you have to draw this flowchart in your exam whenever you are

writing about the fertilization you can draw this one more ah diagram of your second view site where you have to

draw the three layers one is Corona radiator Zona palacida and vitiline membrane and there is a perimeter line

space which is having fun polar body this one polar body is before fertilization and this is your nuclear

material once the fertilization will take place the number of polar body will increase why because the fertilization

occurs once there is a second mutic division completes so second mutic division also produces a polar body so

in this perivateral and space you have more than one polar body clear so my dear students now at the end of this

lecture I hope you have the idea how to write down the Fertilization in exam you have to start with your definition then

you have you should not for forget to write some very important word in your short note like capacitation like

acrosome reaction like the steps of fertilization what is the calcium wave what are the effect of calcium wave and

I am suggesting you that always draw the flow chart in your exam step by step showing the fertilization so this is all

for the lecture thank you