those alright we're gonna go through our lab on mitosis meiosis and gametogenesis so if you could look in your lab supplement and turn to this page this page 1 in your lab supplement has the objectives for today's lab I'm going to keep coming back to this throughout class just to make sure we're covering everything so the first objective has us just looking at some terminology somatic cell gamete zygote haploid diploid so in the reading those terms are defined pretty simply here for you somatic
cells are all body cells so the key word for somatic is body cells so every cell in your body outside of the sex cells sperm and egg we call somatic cells so majority of the cells that make you you are somatic cells they contain 23 different chromosomes and you have a pair of each of those one set of 23 you got from your mom and the other 23 in all of your body cells you got from your dad so you're a combination of the chromosomes from your mom and dad but each 23 for a total of 46 so there's 23
different human chromosomes we inherit one of each from our parents so we call that chromosome number 2n and is the number of different chromosomes we have in the body and how many did I say we have 23 different chromosomes and we have two pairs of those so we say the somatic cells are 2n we have two pairs of 23 chromosomes or one pair I guess I mean if you want to be technical one pair of each right so 23 from our mom 23 from our dad and then the gametes are the sex cells so it's another name
for sex cells so sperm and egg are gametes and they each have 23 chromosomes and that's important because when sperm and egg come together during fertilization in the nuclei of the sperm and egg fuse 23 plus 23 is 46 and that makes a somatic cell so that's the beginning of you and that very first cell formed from sperm and egg the nucleus of each uniting to get 46 chromosomes is called a zygote so a zygote is a one cell organism it that's how we start that's the very first step when those two nu
clei fuse with sperm and egg so how many chromosomes are in the zygote did I just say sperm and egg fuse each bringing their chromosomes together 46 46 so diploid means two chromosomes of the same kind so we have 23 different chromosomes so we have two sets 46 that means we're diploid and if you have one set of chromosomes we see that cell is haploid so that's just some terminology to kind of get things going here now I have a PowerPoint also for the first part of today's lab this is the mitosis
meiosis portion so to review mitosis a couple of things to remember this is from generally impede mitosis is just making a copy of a cell so anytime we need to replace or repair or add another cell we undergo mitosis so what are some times in our lives from beginning to end that we might need to do those things replace repair add new cells yeah yeah our skin Slough Soph we need to replace more so that occurs in the bottom layer of our dermis epidermis our epidermis the stratum basale of epiderm
is undergoes mitosis cardiac muscle cells do they replace themselves not necessarily if they're if they die they're gone but during periods of growth as the heart starts from the size of a baby to a size of an adult we would replace heart muscle cells in that case there are some tissues that can grow back like the liver can regenerate if you lose a part of your liver you know it's a an auto accident you kept lacerations on the liver that can repair and make new cells to replace the damaged ones
bone cells definitely replace themselves if you fracture a bone you can repair that your body will repair that by mitosis so those are examples of replacing and during periods of growth anywhere from infancy to end of puberty that's all mitosis you know occurring constantly making new cells so again when we look at mitosis it's just making a copy machine the cell that we're copying is the same mitosis begins as the long threads of DNA in the nucleus start to coil having already replicated these
threads emerge as the double strands we know as chromosomes so in mitosis before we kick into mitosis ourselves are hanging out an interface where you have a nuclear membrane you have this kind of loosely held DNA called chromatin and all the organelles of the cell just kind of doing their thing undergoing metabolism but when it comes time to replace or repair a cell we kick into mitosis and all those organelles disappear except for those that are important for cell division like the centrioles
and the nuclear membrane breaks down so this is the first stage of mitosis when we're getting ready to divide the chromosomes start to coil and form are the DNA starts to the coil and form chromosomes those x Lake structures so those are these X Lake structures are called chromosomes and these are strands of DNA that have been replicated so remember last week when you had to replicate the DNA right we gave you one side and we had to make a copy of DNA essentially right so this is replicated DNA
so this is one chromosome that's been copied to make another chromosome and then it's attached by a centromere so this is one chromosome that's been copied or replicated so if I count the number of chromosomes in the cell I have 1 2 3 4 5 6 chromosomes in this cell each has been copied but we found it as one chromosome when they're tethered together by that centromere remember the centromere that we learned in general A&P that's what attaches those two sister chromatids together those two pieces
of DNA so we have 6 chromosomes here and 3 are blue and 3 are red so we have one set from mom say the reddish color ones came from mom and the other set came from dad so that's total of 6 chromosomes 3 different chromosomes right we have a pair of each type meanwhile protein fibers grow from the migrating centrioles forming a latticework of spindles for recent scientists don't fully understand the nuclear membrane suddenly disintegrates so this is prophase again again we know nuclear membrane c
entrioles are on either side we can see chromosomes in the middle but they're not quite lined up in the middle they're just kind of hanging out and this spindle is being secreted by these centrioles and the spindle is going to attach to the chromosomes and push them to the middle that's the next phase of mitosis and what is that called metaphase meta means middle so they're lined up in the middle with amazing accuracy a spindle from each centriole attaches itself to each of the chromosomes assis
ted by the protein fibers the chromosomes move center stage in a microscopic tug-of-war the spindles pull each chromatid toward opposite poles so this is the next phase when the chromosomes are being pulled apart what is that phase anaphase being pulled apart so Ana apart so for the lab exam you're gonna have to look at pictures our slides of the different phases of mitosis and be able to identify it so it's a little bit of a review from general ap not many other spindles push against each other
in a ratcheting action that stretches the cell the chromosomes then unwind and the nuclear membranes reform with mitosis complete the nuclei and cytoplasm separate creating two new cells in this ongoing cycle that sustains all life now see how that cytoplasm is pinching inward this animation it happens a little later in the animation actually happens toward the end of anaphase is when that pinching in occurs so the last phase of mitosis where the pinching in occurs but the nuclear membranes hav
en't appeared yet would be called telophase so look for that figure-eight appearance for telophase in the microscope and then you'll see the dark chromosomes in either side of the cell and this process of the cytoplasm pinching inward is called cytokinesis that's another term that you should be aware of so the pinching in of the cytoplasm is called cytokinesis so we have two new selves so going back chromosome number stays the same we had six chromosomes at the end of mitosis we still have six c
hromosomes but are they as sister chromatids anymore are they look do they look like X like structures no now they're single-stranded not stranded but one half of each it's still double-stranded DNA but we only have one half of that X shaped structure that we started out with so the chromosome number stays the same now the other process is much more detailed but it's still very similar to mitosis and that's meiosis so where does it occur testes and ovaries that's it so two locations from for mei
osis testes ovaries and it forms gametes so the cells at the end of meiosis are sperm and egg so the role of meiosis is to cut that chromosome number in half another name for meiosis is the reduction division so it's the division of cells that reduces the chromosome number by 1/2 so there's a meiosis 1 phase and a meiosis 2 phase and at the end of that if you think of meiosis kind of like mitosis times 2 instead of getting 2 cells at the end like we do in mitosis at the end of meiosis we get 4 c
ells so it's almost like mitosis runs twice but there's some slight differences in those processes which we'll look at meiosis is the process that results in the formation of sperm cells and egg cells the cells that will undergo meiosis are typically found in the testes and ovaries of males and females respectively these germline cells are diploid having two sets of chromosomes but will undergo meiosis to produce haploid cells having one set of chromosomes during fertilization these haploid cell
s fuse to form a diploid offspring that single cell that's diploid when sperm and egg fuse like mitosis meiosis is preceded by an interphase during this time DNA replicates and each chromosome becomes doubled consisting of two identical strands of DNA meiosis involves two but they're still considered one chromosome so we have a total of two chromosomes starting out in this cell the green chromosome and the purple chromosome and where did each of those come from mom and dad okay so they replicate
d that's what makes them look like an x as DNA replication happened we have another copy of that DNA attached to that parent copy so now we're gonna undergo meiosis to get this chromosome so there's in in this example this would be one type of chromosome and we have a pair of them right so there's two chromosomes here divisions the first division meiosis one halves the number of chromosomes and in the second division meiosis two the sister chromatids are split the end result is four haploid cell
s so this meiosis one is going to take these two chromosomes and go through prophase 1 metaphase 1 anaphase 1 telophase 1 just like we saw in mitosis same look and we end up with two cells at the end just like with mitosis then this cell is going to undergo meiosis 2 and undergo prophase 2 - anaphase - telophase - just like mitosis to get these two cells and the same thing is gonna happen with this one it's gonna go through meiosis two and end up with these two cells so it's just like mitosis mi
tosis except for there some slight differences now let's look at each of these divisions in more detail meiosis one begins with prophase one individual replicated chromosomes become visible and each chromosome consists of identical sister chromatids joined at their centromeres the spindle fibers start to form and the nuclear envelope disintegrates in addition homologous chromosomes line up next to each other and an event unique to meiosis occurs during this unique event called crossing over two
homologous chromosomes which are lined up next to each other exchange DNA between adjacent homologous chromosomes after crossing over has occurred the sister chromatids of one chromosome are no longer identical to one another so this process is called crossing over but to other terms you need to know if you look at your worksheet for today one is not that one where's the worksheet here genetic variability happens during meiosis so what leads to that the first one is it's called synapses is when
those two chromosomes came together and it formed that four-armed structure where the two x's came together that's called synapses and that structure is called a tetrad tetra means four so if I go back to my animation here so this would be synapses is one thing that leads to genetic variability and that's what happened here is when you saw those four together that process right there is called synapses is just the coming together of like chromosomes so we have 23 different chromosomes so this co
uld be chromosome number one one from mom one from dad that's the same chromosome carry the same type of information we call those homologous chromosomes two chromosomes that carry the same type of information different versions of that information because your mom and dad don't look the same but they are humans so they had those 23 chromosomes with similar information so they came together that's called synapses that structure is called a tetrad because you can see the four strands are part of
a tetrad then when they exchange that information again that was called crossing over so the arms of the homologous chromosomes overlap and they swapped DNA just little pieces of DNA so it's not completely different but this chromosome now has a little bit of mom on it and this chromosome has a little bit of dad on it they both take place at prophase one exactly so crossing over is the second one and that is also prophase one and the last one is the next stage in the process Aysen homologous chr
omosomes after crossing over has occurred the sister chromatids of one chromosome are no longer identical to one another in metaphase one homologous chromosomes line up along the equator of the cell for each pair of homologs the orientation on the equator is random so what that means is this chromosome could have went on this side of the cell and this chromosome could have went on this side so how they line up on the on the middle of the cell is random so when the cell divides like this one here
is mostly mom right so this cell when these two cells divides this half is gonna have mostly moms characteristics on that chromosome right but if it if it they randomly went the other way the green one went on this side then this cell would have mostly dads characteristics on it so if this happens to be the sperm that makes baby that child's gonna look more like dad cuz it inherited that chromosome that had mostly dads DNA on it and you've seen that in families haven't you like all I can tell w
hose baby this he is right or she is because they look so much like the parent or sometimes you have a kid that looks nothing like either parent cuz there's so much variability that happened in this process but the goal is is variability in meiosis so this process of independent assortment is what we call this a random assortment we call that happens during what phase yeah metaphase one so independent or random assortment either term is acceptable and that's the third one for letter C and the st
age is metaphase one now there's another link to variability that's not on the worksheet and that is which sperm is gonna fertilize the egg there's millions of sperm and one ejaculate from a male during orgasm so which one is gonna fertilize that's random also so we call it random fertilization is another source that could be letter D it's not on the sheet so you don't need to know it for the lab exam but it's important to know that that's another reason for that for variation so that's why when
you see a woman who has twins one's a boy one's a girl or even if there are two girls and they look nothing like one another that's because they're fraternal twins which it was two eggs that were ovulated by the mother and two different sperm that fertilized each of those eggs so there are no more related than brothers and sisters born five years apart they were just shared a womb together okay so back to meiosis currently the large purple chromosome and the small green chromosome are on top ho
wever the small purple chromosome could just have easily have ended on top each different orientation results in gametes with different combinations of parental chromosomes this process is called independent assortment once the chromosomes are lined up the ends of the spindle fibers attached to each centromere in anaphase one the chromosomes move apart from one another along the spindle fiber to the opposite ends of the cell at this point each chromosome is still double-stranded and has two sist
er chromatids however we are separating homologous chromosomes into two different cells so that each new cell will have only one member of the homologous pair and will be haploid in telophase one the spindle fiber disintegrates and cytokinesis cell division begins thus in meiosis one which fur presses from prophase one to telophase one two cells are created and each cell has half the number of chromosomes compared to the original cell so we still have this X form the homologous chromosomes which
worse but they were separated now this chromosome was separated from the other one just like it on the other side so there's two chromosomes in this new cell would you agree with that right I'd go back to the beginning when I started out there were how many chromosomes four so meiosis one takes the cell from 46 down to 23 so at the end of meiosis one we have two cells each with 23 chromosomes all right so now we'll continue after cytokinesis is complete a second division or meiosis two starts t
his division is identical to mitosis and the resulting cells have the exact same number of chromosomes as the original cell at the end of meiosis one in prophase two we now have two cells each with two chromosomes in this stage the spindle fibers again start to form at the poles of the cell in metaphase to the chromosomes line up along the equator this is different from metaphase 1 where the homologous chromosomes were lined up in metaphase 2 each cell has only one of each homologous chromosome
in anaphase 2 the sister chromatids move away from each other along the spindle fiber and in telophase 2 along with cytokinesis we see the formation of four genetically different haploid cells okay so four different cells has the chromosome number changed from meiosis one to meiosis two yes no louder no we had 23 at the end of meiosis 1 and we still have 23 but what's the difference when looking at mitosis or meiosis 1 and meiosis 2 I made a little worksheet here for you to help with that it has
a model let's go to this here it's called lab it's called models and slides document be sure that you look at this and label it or understand the different parts so here's the model we have in lab of mitosis so what would this phase be here say it louder interphase right because we can see a nucleolus see a nuclear membrane number 2 is 2 & 3 our prophase 4 is metaphase 5 is metaphase Six's anaphase they're being pulled apart and 7 would be telophase cytokinesis is occurring and at the end we're
done so that's mitosis now if I look at this model here you can make it a little bigger okay so if I look at this model this is our meiosis model so here I have interphase interphase right now I see some chromosomes showing up so this would be prophase 1 this would be prophase 1 here I have my chromosomes coming together what do we call this process where they come together synapses and this structure this four stranded structured tetrad so I have two homologous chromosomes that have come toget
her synapses they're swapping some DNA what do we call that crossing over so this is prophase one look for the the two x's next to one another because we can take each of these little pieces out of here and put these on as a separate question on the test so don't memorize these in order I mean it helps to learn it that way in the beginning but be able to pull them out separately and a really good idea would be to print this off and make flashcards and then put it on the other side what phase it
is okay so there in order for you now but cut them up and make flashcards and be a great way to study so this is prophase one this would be what comes after they're lined up in the middle metaphase 1 anaphase 1 they're being pulled apart telophase 1 then this would be an a phase 2 they skipped over prophase 2 and metaphase 2 and went right to anaphase 2 and then this would be the end telophase 2 so now here's a little hint if you look at the model if it has the chromosomes in the version of an e
x which means you have sister chromatids you can see the chromosomes has that that ex structure then you know you're in meiosis 1 so if you can just identify are they lined up at the middle either being pulled apart do I see X's you're in meiosis once you're gonna say prophase 1 metaphase 1 anaphase 1 if they're as single chromatids see they're not X's anymore in these examples then you know you're in meiosis 2 so it's gonna be this one of the anaphase 2 so look for the single strand you know th
e single sister chromatids being pulled apart in meiosis 2 does that make sense all right going back to our objectives then so we talked about mitosis we looked at the different phases of meiosis we talked about the different processes and when they occur when does chromosome reduction occur the specific stage telophase one very good telophase one crossing over we said occurred prophase 1 metaphase 1 independent resort assortment and synapses tetrad was prophase one also so comparing the two let
's go back to the PowerPoint then if we compare the two processes and these are the just the the processes described so you can watch that again if you want but if I compare the two processes mitosis and meiosis we both start out with diploid cells meiosis is going to multiply that cell will talk about this we get two gametogenesis it'll make more sense but let's just start here so we're gonna have this cell that's going to divide into two haploid cells mitosis forms two diploid cells that are t
he same as the parent cell this cell is gonna divide again during meiosis two to form two more haploid cells same thing with this one two more haploid cells so comparing the two four haploid cells at the end versus two diploid cells at the end everybody agree with that and then we have some variation you know genetic variation that happens in prophase 1 metaphase 1 in telophase 1 here's just a written description of those two processes read that on your own prior to meiosis or mitosis DNA replic
ation occurs in both meiosis and mitosis the nuclear membrane breaks down as the DNA organizes into chromosomes in meiosis chromosome pairs come together or synapse and crossing over occurs resulting in mixing of the genetic information between the chromosome pairs the paired chromosomes then align along the central plate of the cell and subsequently separate one travelling to each end of the cell in meiosis a second division sequence occurs resulting in four cells with half the number of chromo
somes mitosis involves a single division sequence resulting in two cells with no net change in the number of chromosomes so here we have two cells two chromosomes here that you have four cells with half the number of chromosomes they both started out the same okay so the next slide PowerPoint is looking at gametogenesis so now we right now that we understand what mitosis and meiosis is now we're gonna apply these processes to the process of making sperm so spermatogenesis is the process involved
in making sperm cells olá genesis oh two O's together we say in science oh oh oh Genesis it's how you would say that is the process of making eggs in the female by meiosis and gametogenesis is the two combined so making the process of making sperm and egg through meiosis we call that gametogenesis making the gametes so spermatogenesis making sperm orogenesis making egg gametogenesis either one sperm EO Genesis refers to the process of making a viable sperm so you have a haploid sperm spermatocy
te there's sperm at it I mean and we want to turn it into a spermatozoa so it's just the process of sperm development and maturation so that's just when we already have the sperm we're just developing it to become a viable swimming one-celled structure so that's oh genesis it's just sperm development the kind of a late process that occurs so we're gonna start with spermatogenesis and then end up with gametogenesis can't go back to our blackboard page here we go I have a handout here it's a blank
diagram I'm just gonna pull this up this is for you to label and practice with this is formatted Genesis here this is OA Genesis what I would recommend is that you name these cells and give them a chromosome number of either n or 2n and that's gonna help you on the test because he'll have models diagrams written questions in the lab exam related to the names and the diploid number or chromosome number of these cells so this is what's going on in the ovaries this is what's going on in the testes
and these are both from those diagrams are both from your textbook so here's the PowerPoint okay so commuter Genesis process of making gametes so these come from the starting cell that leads to sperm and egg we call those germ cells so they are destined to be sperm or egg so somatic cells are body cells that are just part of the embryo they're growing and making more of a tissue and making that tissue bigger and bigger but germ cells are destined they're like stem cells right you've heard of st
em cells so these are unspecialized cells but they're specialized to the point that they're going to become sperm and egg so they're not completely blank they are destined to be sperm and egg but they're very early cells that have not differentiated so if you have a mutation in a germ cell that was used to form you like your dad when he was forming sperm cells there was a mutation there in that process then that would be inherited you would inherit that change in your DNA and that would be a ger
mline mutation like we said is inherited somatic mutations ever we said are you know can cause cancer they can happen in any body cell just they're isolated where germ cells would be in every cell cuz you inherit that DNA from the very GetGo as a zygote so let's talk about spermatogenesis so sperm are made in the testes and the specific structures within the testes where the sperm are formed are called the seminiferous tubules so if you look at the testes do a cross-section in your textbook has
a nice picture of the seminiferous tubules look like from the outside so if you cut a testes in half they kind of look like if you know what the what ramen noodles look like it's just a network of tiny tubules and what we're looking at in this diagram is a cross-section of one of those seminarist tubules and can you see the hair like flagella at the end of a sperm that are kind of clustered toward the center of that picture so that's the center of the seminiferous tubule and the wall of that tub
e you'll is where those sperm cells are formed so out here at the very edge is where you would find the germ cells that are diploid that are destined to become sperm so as sperm develop they work their way inward inside this tube you'll until they break free and with their tails swim away and then they enter the vas deferens and out and enter the female and fertilize the egg so here's a tissue slide of a seminal first tubule in the testes so the organ is the testes the specific structure in the
testes is the seminal first tube you'll and you'll need to know all of these structures other than the suspect a killer cell you don't need to know that one or the basement membrane but you do need to know all these other cells in a tissue slide for the lab exam so on the very outer edge I said are the very beginning cells that are diploid so we'll pick this one here this has the label spermatogonium more than one spermatogonia so a spermatogonia the way I remember this it sounds kind of silly b
ut it's going to be a sperm okay using farm language Midwestern slang okay so it's destined to be that but it's not there yet so this is a diploid cell it has 46 chromosomes or 2n it's on the outside destined to come and become a sperm cell so 46 chromosomes and this diagram I took from or the next diagram I'm going to show here is a really good explanation explanation is figure twenty seven point nine in your text so let's go to this picture this is the one from your textbook 27.9 figure twenty
seven point nine in the newest edition it's on page 1040 and that's the one that I have attached in blackboard as a blank copy for you to label for practicing okay so what happens here is we have this stem cell and this stem cell out here on the edge as a again a spermatogonium and it undergoes mitosis to form another cell that's going to move on and become a sperm so this one is just you don't you can still call it a spermatogonium they call it a daughter cell it's from mitosis of this cell so
if this cell undergoes mitosis wouldn't I have to I'm saying mitosis so that means two cells that are each 46 what everybody agree with that right so this one is gonna stay the type-a daughter cell stays here to keep that DNA for a future sperm and then this one is going to come down and divide and leave the edge of that seminarist tubules so this one's going to come down it's gonna divide by meiosis one into two I'm sorry into a primary spermatocyte and a primary spermatocyte is 2n undergoes m
eiosis one to form secondary spermatocytes so secondary spermatocytes if they underwent meiosis one what would the number here be for chromosome haploid or diploid haploid so 23 chromosomes in each of these so the secondary spermatocytes has 23 chromosomes or haploid the primary spermatocyte had 46 or diploid then this cell is gonna divide into two to form these two cells so this one divides by meiosis two to form these two this one divides through meiosis two to form these two so we have a tota
l of four after meiosis two just like we saw in the generic example we went through and these are called spermatids so how many chromosomes and the sperm attends 23 are haploid again right so you write the letter n there so you can label that in there these are all N and their names early spermatids these are also n there's only two of them secondary spermatocytes and this is 2n 46 chromosomes primary spermatocyte and then out here on the very edge spermatogonium also 2n so then this process of
taking these spermatids and forming the cytoplasmic bridge condensing the material the intracellular material into a neck and a flagellum so they're active swimming sperm then we call them spermatozoa but that whole process going from spermatid to spermatozoa that process is called sperm EO genesis oh genesis so when does this process occur when we go from spermatogonia to spermatocytes so we're starting sperm development it starts at puberty so boys don't start making sperm until 12 13 14 all t
he way up until death it slows down for sure because there's other cells that influence firm development and that's the cells that secrete testosterone so these cells in between the seminiferous tubules are called interstitial cells inter means between so there between the seminarist tubules these little clusters called interstitial cells their job is to secrete testosterone so these cells become a little sluggish as men age and they don't secrete as much testosterone which doesn't support as mu
ch sperm development so sperm development slows down with age but it still occurs and if a nine-year old man is able to participate in intercourse he could you know father a child or they could even go and retrieve the sperm from the epididymis and take sperm that way and you know do it through in vitro fertilization and that has happened so it begins at puberty talked about what is formed in meiosis one it forms two secondary spermatocytes at the end of mitosis two we have four spermatids again
they're not moving cells they're non-modal but they're close to the inside edge so they're close to that hollow center ready to fly ready to swim but they have to undergo sperm e oh genesis to have the flagellum the head in the neck and proceed so that's the different parts so sperm e oh genesis is that process of spermatid to sperm so how long does it take from becoming a spermatid to being a mobile sperm about twenty four days so here is a diagram nicely labeled with all the different chromos
ome numbers so this is a great study tool it has the name of all the different cells it shows you the chromosome number along the way and just know that it works from the edge of the tubulin in word so let's watch this animation this is a really good animation that illustrates the process spermatogonia are the cells from which sperm cells arise the spermatogonia divide by mitosis one daughter cell remains a spermatogonium and the other becomes a primary spermatocyte the primary spermatocyte divi
des by meiosis to form secondary spermatocytes secondary spermatocytes divide again to form spermatids the spermatids differentiate into sperm cells and they're often swimming alright so let's look at the worksheet and we still have that pulled up somewhere no I don't all right so we'll go back to this and look at so number 11 and what organ does spermatogenesis occur the organ testes and the structure Semin if first two alleles good and then we'll go through the rest of these after we finish up
our Genesis okay one other thing I want to refer you to and that is the worksheet that has the different structures on it this one so we looked at those here's a mitosis slide so if you look at this slide what which phase of mitosis is this representing anaphase and this one they're kind of lined up along the middle metaphase this one also metaphase how about this one here cytokinesis yeah at the end of which phase telophase telophase because we're at the end you can see there they're almost se
parated but not quite you can see visible chromosomes no nuclear membrane yet so that's telophase and each of these with just a regular circle and the visible nucleoli the nucleolus in the middle of that nucleus these are all interphase so if you don't see any chromosomes and you just see a pink or dark circle in the center that's a nuclear membrane and that's just a resting phase interphase so I put this put this up here that's kind of a something to refresh your memory on so here's a slide of
a seminarist to Buell so out on the edge here these cells would be permits we're on a very edge it's going to be a sperm stuck in the edge spermatogonia MIT spermatogonium so if it's right here on the very edge if you see a cell pointer on the edge spermatogonia how many chromosomes 46 if I point to these cells here that don't have tails yet but they're here what would these be spermatids how many chromosomes are what's the description for chromosome number 23 haploid or n okay and then if I go
in the middle here these might be secondary spermatocytes but it's really hard to see if they're you know secondary or primary but we can with a reasonable degree of confidence say that these are the spermatogonium that are on the edge these are the spermatids here on the inside lining and if they have a tail attached then they would be spermatozoa right at the very end of that development and what do we call these cells in between the seminar first two alleles here st. loader interstitial cells
yes interstitial cells so here's another one that's been labeled for you which is nice so you can look at that use that for a study tool so this is all in that handout I attached okay so now let's compare this process to what goes on in the ovaries so in the ovaries not on the edge the ovaries are just a mass of tissue so they're just some cells and tissue different types of cells you know about the size of a plum maybe a little smaller than that maybe a large grape is about the size of what an
ovary is in the human so there's this these cells that are germline cells just like we saw in spermatogenesis but in egg or in the ovary they're called Livonia or one of them we call algo neum it undergoes mitosis one is gonna stand all going in because we don't want to lose that DNA so one is gonna stay an old going in and one is going to grow and develop and become the different cells of oogenesis so an old gone IAM that grows and develops becomes a primary oocytes so just like we had the pri
mary spermatocyte that had 46 chromosomes that the ovary has a primary OS a ol site with 46 chromosomes so it undergoes meiosis one to form two secondary oocytes but we don't get to secondary oocytes like we would expect what we get how many eggs do we need what is the body what is the human body designed to grow and develop how many babies one that's ideal right for our species one child is enough because how long does it take before that child is mature and ready to leave home 25 six years no
but it's pretty helpless right when its first born it's not like a like a pony that comes out and is running across the pasture hours after birth right maybe not running but hobbling wobbling across the pasture you know newborns can't do that so we're designed to have one baby so we only need women we don't need a million eggs right men need a million sperm because a lot of those sperm aren't gonna make it up the reproductive tract to find that egg so more volume or higher numbers I should say s
perm are going to ensure fertilization but women you know females only need one egg to be fertilized so only one egg is actually developed in this process of oconee of oogenesis so we had the oboe Neum and at the end we're gonna have one healthy mature egg after meiosis one and meiosis two so here's what happens just lichens spermatogenesis this primary oocytes splits but instead of having two secondary oocytes we have a polar body look at how much smaller it is most of the cytoplasm and the ten
sive this original cell went to this secondary oocytes because this is the one that we want to become a mature egg this one is a polar body it's just kind of fizzles away doesn't have enough information to become an active living cell so we call it a polar body okay so that's meiosis one meiosis two what happens meiosis two occurs and we have a mature ovum and this might in another polar body right because this is gonna split into two after meiosis 2 so we have ovum and another polar body and th
is polar body if it has enough information it could undergo meiosis 2 again and we could and we should have four at the end right just like we've said with meiosis we always have four haploid cells at the end so if this one did divide again in meiosis two we could have one two three four cells like meiosis two should provide but with eggs we really only need one mature egg so these polar bodies degenerate and they don't really have any function so this is where all the action is this is what we
want so this is a haploid cell so Olga Nia becoming primary oocytes that's just mitosis we just make a copy of that cell they're both 46 they're both diploid cells when do these form before that woman is even born is when all these primary oocytes are formed so this mitotic process of making of taking all Gonia and making a primary oocyte happens before birth 7,000,000 primary oocytes there'd be a lot of babies wouldn't it so we don't need that many in our lifetime a woman only produces one egg
a month during a reproductive years to be fertilized so that number is cut down throughout life so only a million of the seven million produced will remain at birth some of them degenerate the undergo a proptosis and then from birth to puberty only 300,000 remain that's still a lot of kids in a woman's lifetime so she's never gonna use all 300 those eggs so what happens then is the primary oocytes enter meiosis one but they're stuck in prophase 1 metaphase 1 until puberty so this development thi
s meiosis is occurring during childhood but it stops until puberty so it's stuck in that prophase 1 metaphase 1 phase so here's an ovary so on the very edge are these primary oocytes and the cells around them are called follicle cells they just nourished that nucleus that developing ol site so they're just supportive cells and they're found they're much smaller sometimes found near the edge but not always and then when it comes time for puberty and ovulation leading to fertilization some of thos
e cells will be picked to develop and become a mature oocyte a secondary oocytes to be ovulated and that's what this one is this is a secondary oocytes that was ovulated released from the ovary into the fallopian tube waiting to be fertilized by a sperm so the process of going from primary oocytes to secondary oocytes then is each month after puberty during the menstrual and ovule Ettore cycle is when this development from primary oocytes meiosis so what which stage of meiosis are we in 2n 2n me
iosis 1 or meiosis 2 are both both yeah meiosis 1 is gonna cut the chromosome number in half right so the primary role site to the secondary oocytes is meiosis 1 then meiosis 2 begins but that secondary oocyte is stuck at metaphase 2 so when this is when this secondary oocytes is released at ovulation it's stuck in metaphase 2 so the chromosomes are lined up on the center of the cell it's ready to separate right but that has not happened yet until fertilization if fertilization occurs then it sp
lits and metaphase 2 completes and meiosis 2 completes only after fertilization so it's stuck in metaphase 2 until fertilization so some questions you might see in the lab exam is when these cells are formed okay so a primary oocytes is formed when a primary oocyte is just mitosis from ogo Neum so during after birth let's go back primary oocytes are formed during fetal of the fetal period and then their number is just reduced up until puberty so secondary all the sites are not formed until after
puberty so primary oocytes are formed during the fetal period so again this is a nice chart because it tells you when everything is occurring so before birth childhood puberty - menopause so these are the reproductive years here so here we can see again mitosis takes thatö ago Neum forms a primary olla site and that primary oocytes is gonna just hang out until puberty then it's 1 then it will be chosen to enter meiosis and become a secondary oocytes and it'll be stuck there until penetrated by
a sperm once it penetrates when it's penetrated by a sperm then it becomes a mature ovum so after fertilization we have all of them so this is again 4 cells we know that meiosis produces four haploid cells but again three of those cells are polar bodies that are not useful not necessary for reproduction the egg is what we care about the ovum now there's another column of information here I'm going to go back and talk about that so these cells like I said that supportive cells around the developi
ng nucleus and cytoplasm of this Oh site are called follicular cells follicle cells so when the follicle bursts and releases that secondary oocytes some people feel pain and ovulation and when I taught health years ago at UWL sometimes we talk about fertility and reproductive system and I had a student come up and say you know I'm worried that I might have ovarian cancer or some problem because I get really bad pains every month it lasts for a couple of days and I can't hardly sit down I'm in su
ch pain I have to take ibuprofen and I it's not want to have my period I'm not having my period when I have these pains and it's really bad sometimes and what she was experiencing was ovulation pain is when that ovary ruptures and releases that secondary oocyte prostaglandins are released and that causes pain over that side so if you're female you may have noticed if you notice some people can't feel of ulation some can you may have noticed you have a dull aching pain about two weeks before the
minister period would start and it alternates now the ovaries don't always go left right left right you know evenly sometimes might be left left right right left right there's no real pattern to it but we know that the ovaries both you know take turns only one ovary releases one egg each month but when you get to be over 35 but there seems to be a peak between the age of 35 and 40 where there's a period of time where women tend to release two eggs and that's where you see an increase in fraterna
l twins because they released to AIDS that particular month does anybody know anybody who had twins they've got pregnant over 35 you know somebody yeah and they were not identical correct oh okay okay it's hard to tell while newborns look the same right yeah but typically they're not because it was two eggs two different sperms so two different babies but anyway so these follicle cells so then that follicle is called a corpus luteum luteal refers to the color yellow it's like a Latin or Greek pr
efix I'm not sure which one but so this is a special you know organ within it's a tissue is to say within the ovary that starts secreting hormones and it secretes progesterone and if this egg became fertilized by sperm and pregnancy starts that corpus luteum is going to continues to secrete progesterone which supports the uterus and maintains a pregnancy so that's a really important structure and it's the remainder of those follicle cells after the egg has left after the second areola site has l
eft and some women will find when they are early pregnant that they have a little discomfort on the side even though they're pregnant and babies in the uterus you know down low between the hips they feel that akon that one side and again that's a corpus luteum cyst that can remain there that that was the egg that was there from one baby or when that secondary oocyte was ovulated that formed baby some people the cyst gets quite large and can be damaging or dangerous I know someone who they talked
about maybe having surgery to remove that cyst I don't I don't know I don't think she ever had to have surgery but it was a concern for a while so I don't know what happened there but that's the corpus luteum but now if pregnancy did not and it'll grow bigger until the placenta grows and the placenta is what attaches to baby and we'll be talking about that next know two weeks when we talk about reproduction and fetal development then the placenta will take over all that hormone production and t
he corpus luteum will shrink down and become less important so this is just comparing well one more thing I should talk about is there's an animation I'm gonna go to that talks about the corpus luteum before we go any further questions exactly yep yep and that happened with one of my pregnancies it's just one of those weird things and it was not my last one it wasn't an early one it was just one of those weird things and it's a good thing to know that because some women who have a lot of early p
regnancy losses early bleeding and loss of the pregnancy after a positive test it can be something as simple as low progesterone and taking out getting a blood test testing checking for juster on levels they can supplement a woman with progesterone until that placenta kicks in and then the placenta does the job and they don't have to supplement with progesterone anymore and it can prevent the loss of a pregnancy so really important test okay so let's watch this corpus luteum and if pregnancy doe
sn't take place secondary oocytes here is not fertilized then this breaks down and becomes a corpus albicans so it's a white structure that we see on the ovary and what do we call a person that has white skin white hair and red eyes albino alba means white so that's where corpus albicans comes from then I'll help you remember that word Alba meaning white luteal means yellow a primordial follicle consists of an O site surrounded by a single layer of squamous granulosa cells a primordial follicle
becomes a primary follicle as the granulosa cells become enlarged and cuboidal the primary follicle enlarges and the granulosa cells form more than one layer the zona pellucida forms around the o site the structure is called a secondary follicle when fluid-filled vesicles develop among the granulosa cells and a well-developed capsule or Thika becomes apparent around the granulosa cells there's a lot of extra terminology in this video that you don't have to know you don't have to know all the dif
ferent names of the follicle cells just know that this is the what is this Oh a sight and then we're gonna talk about some of the structures after it's ovulated the theca possesses internal and external layers the structure is called a mature follicle when the fluid filled vesicles form a single antrum at full maturity the OSI is located in the cumulus mass during ovulation the Oh site is released from the follicle along with some surrounding granulosa cells of the cumulus mass called the corona
radiata following ovulation the granulosa cells divide rapidly and enlarge to form the yellow corpus luteum when the corpus luteum degenerates it forms the white corpus albicans okay so when this secondary oocyte is ovulating there's some follicle cells that remain around it and this is a term that unity do need to know and that's those cells are protective cells called the corona radiata and the sperm have to penetrate through those cells to get to that egg and there's another layer it's calle
d the glycoprotein so it's a protein with sugar attached to it call the zona pellucida see the white here it's smooth it doesn't look cellular it's just a smooth outer covering of that aid again called the zona pellucida that the acrosome if you remember the enzyme and the head of the sperm from general A&P that has to dissolve that zona pellucida caused a chemical reaction to allow that sperm nucleus to enter that egg once it enters once that sperm enters the egg the zona pellucida hardens almo
st like an eggshell you can just use that analogy so no other sperm will enter because there's millions of sperm working their way through the cells of the corona radiata trying to get to that egg but once that one the first firm gets there that zona pellucida hardens and shuts down and will not allow another sperm to enter because we don't want more than one sperm because that means more chromosomes and we have to have 46 chromosomes to into a viable zygote human being okay so here is the zona
pellucida that white outer layer so you will see a slide in the lab exam about the zona pellucida so be sure that you are able to identify that and then the corona radiata I would again maybe these cells around the edge here and in that other document here I have a picture of that this is the only one I could find that had the corona radiata all right yeah the corona radiata all those cells corona radiata and then this white even layer zona pellucida here's an ovary with a large corpus luteum so
these can you see these empty follicles here but this is the large corpus luteum that actually ovulated that secondary oocytes so that's what this is a picture so be sure that you look at this handout here and identify the structures so again primordial follicles so we see you know one cell not a lot of follicles around it here's a primary oocyte getting a little larger here secondary oocytes much larger has a big fluid filled space to put another picture I don't see that I have one of a second
ary follicle I'll find one and put it up on blackboard okay so going back then comparing the two processes spermatogenesis in oogenesis spermatogenesis we have 4i you know for sperm cells but again through meiosis one and two there's some genetic variation that occurred right synapses crossing over independent assortment so we still have four cells here in oogenesis but really only one egg these polar bodies are the other cells that are not functional and the ovum is only called an ovum after it
's been fertilized by sperm prior to that is called a secondary oocytes so what's a view lated is a secondary oocytes but again similar process is just the names of the of the cells are different this is a nice picture of showing the zona pellucida in pink and the dark cells of the corona radiata here's just an example of how the sperm has to work its way through those cells and then that acrosome has that interaction with the zona pellucida here we can see here this one entered and the nucleus
of the sperm combines with the nucleus of the egg to form the what is that what is it the zygote yep the zygote and we'll pick up in two weeks with how that development occurs so now let's look at your worksheet that I handed out so number one formation of OVA and polar bodies is what process Oh a Genesis and the general term for a process that involves meiosis gametogenesis yep letter B the manner in which the zygote is gonna divide so when that zygote is formed now it's gonna grow and develop
what process is that yeah mitosis mitosis an undifferentiated diploid male reproductive cell its diploid so it's 2n yep spermatogonium maturing maturation of spermatid so we're taking the spermatid and maturing it into a viable moving sperm yes Fermi Oh Genesis and the daughter cell of meiosis one in the mail so after meiosis one we have yep secondary spermatocyte and the creation of sperm that whole process from spermatogonia to spermatozoa is spermatogenesis yep so the next one the next questi
on is what are a what are the two things released in Ulan what's the one thing I repeated over and over secondary oocytes and what's the partner from meiosis one that goes with that secondary oocytes that's small little useless cell yeah the first polar body we'll call it and the layer of glycoproteins surrounding the gametes in women and females no the corona radiata zona pellucida think of it like a zone it's like the outer layer that needs to be penetrated for fertilization follicle cells sur
rounding that layer corona radiata yes so after the sperm penetrate it completes the second division resulting in two haploid cells what is that cell called after it's been fertilized ovum and the other cell is yeah the second polar body number 10 we did already number 11 we did already number 12 Oh in Genesis what organ the ovaries and what is the structure where the cell is developing and all those cells around it what are all those cells around it collectively called follicle yeah follicle we
're in what structure does meiosis to occur this is tricky now meiosis to occurs it finishes it completes after fertilization right so this is asking where does fertilization occur yeah in the fallopian tube or uterine tube and number 13 that solid structure that those follicle cells form is called a corpus luteum which secretes progesterone and that concludes lab the lab exam
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