hi everybody and welcome back to miss angler's biology class i am miss angler and in today's video we are going to be looking at fertilization and implantation now if you're new here don't forget to give this video a thumbs up subscribe and turn those notifications on so that you get the newest videos every tuesday and thursday for grade 8 to 12 a biology so let's get into the video now today we are going to look at specifically the changes that occur in a zygote after fertilization and then into implantation now it's important that before we get into the details of how this occurs you need to be very familiar with your meiosis stages so i suggest you go and click the link above now to make sure you understand how meiosis works but you also need to make yourself very familiar with the structures needed in the female reproductive system as well now to make sure that we are all on the same page it's also really important to know the structure of your egg and sperm cell you can also go look at my spermatogenesis and ogens videos which i've just linked above now where i explain how each of these cells are produced you will need to know that for tests and exams and you will also need to know the functions of all of the structures that we find within these cells you also will be asked to draw them label them so i suggest that you're very familiar with both of these types of cells first before we get into fertilization and then implantation now getting into the actual steps of fertilization you'll see a diagram like this it's very common to see this in textbooks as well as exams except of course the exam ones generally have fewer labels because they want you to be able to identify certain things now let's just trace the development of a egg all the way through to fertilization so at this point you should all be very familiar with the ovarian cycle and if you haven't again please go and have a look at my menstrual cycle video where i explain that and essentially at this point ovulation has occurred and that is when a um egg cell has been released out of the ovary it's mature now and it is sitting in the fallopian tube so it bursts out and we end up in this space over here and so now our egg is going to wait in the fallopian tube this is the site of fertilization that's a very common question that we see in exams and essentially what happens is um sperm cells are going to make their way over to the egg they sense the egg via a chemical message that they can receive from the eggs they know where to swim and basically they all start to try and burrow into the egg only one sperm cell is successful though and that's important um for every one egg there can only be one sperm cell in a later video i will explain how it's possible then to have you know twins but essentially one sperm cell burrows in and it leaves behind its tail and its neck and the only part that actually goes into the egg cell is the head of the sperm cell and that's where the nucleus is now when you are describing this in an exam i need you to make sure that you speak about the fact that after the sperm cell has burrowed in the sperm nucleus and the egg nucleus are going to fuse and this is an important step because this is where we are taking a cell which is in which represents haploid and our other cell which is also haploid we're taking two pieces of information that are haploid and we are forming a zygote cell which is diploid it has its full complement of chromosomes now once fertilization has happened in other words the sperm cells have oh the sperm cell has um inserted its nucleus with its dna and the two nuclei have gone and combined with one another they form a zygote now that zygote is still one cell as you can see on the inside of this particular cell there is only one cell membrane which is this here that i'm just going to quickly draw around the edge that you can see then what happens is we undergo mitosis and that is what you are seeing in this section over here and so what we end up having is one cell becomes two cells two become four four become eight and so on and so we're going through a process of mitosis and that's also why you need to be very familiar with the process of mitosis and its purpose again if you can't remember this from grade 10 it was some time ago i suggest you also go and have a look at the lady video that i've linked above now once mitosis has occurred um enough we end up with a solid wall of cells called a morula now it still has this protective layer on the outside that we can see so that is not the cell everybody remember it's all of these little pink structures on the inside that is the cells and it forms a marula now if we go back down into our diagram of our uterus i want you to just trace the image as we've gone along so fertilization has happened in the fallopian tube and slowly but surely our fertilized egg our zygote now that's what we need to call it the zygote moves along the fallopian tube inside the fallopian tube there are cilia which are tiny little hairs that beat backwards and forwards and they're basically like a conveyor belt move the egg from where it was fertilized so over here and they're going to move it all the way down until we get to here where we are right now and we are trying to implant this egg because eggs cannot grow in the fallopian tube there's not enough space and so as the egg makes its way now down into the main compartment of the uterus it's going to keep growing and what it's going to do is it's going to form something called a blastocyst so you'll see it's the next step the difference here is if you have a look the blastocyst is hollow on the inside and that is because this is the early stage where we're actually starting to grow our tissue layers where we're going to grow our triploblastic layers which you may remember from grade 11 where we have our three tissue layers which grow into the three different compartments of our body now eventually that blastocyst is going to literally sink into the wall of the uterus and if we just have a look over here where i'm pointing to now we can see that the blastocyst is sinking into specifically the endometrium now remember the endometrium was thickened and made more vascular and glandular by progesterone and estrogen assisted in initially regrowing the layer after the menstrual cycle had completed and technically now pregnancy has occurred from this point onwards if you took a pregnancy test it would be positive now i know that particular diagram is intimidating there's a lot going on there and you feel a little bit lost so let me explain with a very very simple diagram one last time to summarize first things first we have an egg cell and a sperm cell that come together via fertilization where the sperm cell uses its acrosome to burrow into the egg cell and we end up fusing the nucleus of the sperm and egg together remember they're haploid cells and we want to make a diploid cell so they're going to fuse their nuclei together and they are going to form a structure called a zygote a zygote is diploid has all the chromosomes it needs and it's going to undergo my ptosis and mitosis is going to produce the first group of cells called a morula which is a solid ball of cells that is going to continue to undergo mitosis and we are going to form a blastocyst which is a hollow ball of cells and you can see the ball is hollow on the inside now to take it a step further some of you may have this information in your textbook and i'd like to point it out it is important if it is not in your textbook to make note of this the outer layer of the blastocyst which in this particular diagram is represented by this white uh layer of cells on the outside here that is known as the trophoblast and that is the outer tissue layer it is the tissue layer that is going to grow into your skin and your nervous system whereas the yellow colored layer of cells on the inside is going to become all of your internal organs and so it's important to remember that once we're a zygote and we are now diploid which means we have a full set of chromosomes we are then going to undergo mitosis all the way through here all the way until you're born in order to go from just a group of cells of four or six to billions of cells that you are now now as always i like to finish off my lessons with a terminology recap and you can use all of these terms to create flash cards to study from we looked at first of all sperm and egg cells which of course we know are the gametes that we need in order for fertilization to occur and we spoke about what fertilization was it is when the nuclei of a egg cell and a sperm cell come together and they fuse and they go from being two haploid cells to a singular diploid cell which remember refers to the amount of chromosomes that they have once they have fused together they form a cell called a zygote that zygote undergoes mitosis and it replicates from two cells to four to six to eight etc and it becomes a solid ball of cells called a morula now it's important to remember all of this is taking place in the fallopian tube and it's slowly making its way down to the uterus once it receives the marula in the uterus it continues to develop into the blastocyst which is a hollow ball of cells that hollow ball of cells has an outer layer called a trophoblast and that trophoblast is going to grow into your external tissues like your nervous system and your skin and the inner layers are going to become all of your internal organs that blastocyst is going to implant or go through implantation where it sinks into the endometrium lining and the endometrium surrounds that ball of cells and it continues to develop into an embryo now if you've liked this video don't forget to give it a thumbs up subscribe and turn your notifications on everybody because i post every tuesday and thursday and i hope you've all enjoyed this video and i'll see you again soon bye you