Lesson video

Hello, and welcome to this lesson from the unit "Hormones and human reproduction." The title of today's lesson is "Hormonal Control of the Menstrual Cycle." So we'll be looking at the names of the different hormones involved in controlling the menstrual cycle and the processes that take place.

My name's Mrs. Barnard, and I'm going to be taking you through today's lesson.

So by the end of today's lesson, you should be able to explain the roles of FSH, LH, oestrogen, and progesterone in controlling the menstrual cycle in human females.

So we've got quite a few key words in today's lesson.

So we've got ovulation, FSH, oestrogen, LH, and progesterone.

So if you want to write down those definitions, then you can pause the video, but otherwise we will be going through it as we go through today's lesson.

So our lesson today is in two parts.

The first one is about the hormones, FSH, LH, and oestrogen, and the second one is progesterone.

So let's get started with these first three hormones here, FSH, LH, and oestrogen.

So a little recap.

The menstrual cycle involves processes that take place within the female reproductive system, and that's our reproductive system labelled there, hopefully everybody recognises that.

And these processes are controlled by hormones that are secreted by the ovaries and the pituitary glands.

So the ovaries are glands too.

Our pituitary gland is up there in the brain and our ovaries are there at the bottom.

The process involved in the menstrual cycle are ovulation and menstruation.

So menstruation is traditionally where we start numbering the cycle and that is when the lining of the uterus breaks down.

So that will be because an egg has not been fertilised and therefore does not need to implant in the uterus lining.

So it will pass out through the cervix and the vagina along with the uterus lining that is not required.

Then as we continue the cycle, the uterus lining regrows preparing for another possible fertilised egg.

Then ovulation occurs, and we can see ovulation at the bottom there, between days 15 and 19, you might be able to just see that little yellow egg that's coming out.

If it's fertilising the fallopian tubes, this menstrual cycle will stop because the hormone levels will change.

But otherwise it will pass into the uterus and then the whole process begins again with that unfertilized egg and the uterus lining passing out.

So this process occurs in a cycle, so really you could number it from anywhere.

We just traditionally number it from zero, first day of menstruation, and each cycle lasts a number of days.

This does vary.

So even in models where it is shown as 28 days, that can vary between different females.

So 28 is the average length, and also the number of days that each part of that cycle takes place over also varies between different individuals.

So let's look at exactly what happens at each point in this cycle.

So at days 0 to 5, the uterus lining breaks down and menstruation takes place.

Then day 6 to 14, the uterus lining starts to reform and thicken.

And on day 14, again, there is variation there, an egg is released, and that process is called ovulation.

At days 15 to 90, the uterus lining continues to thicken as the egg travels down the fallopian tube.

And finally, at days 20 to 28, the uterus lining is maintained in case the egg is fertilised.

And if the egg is not fertilised, the cycle will then continue.

If the egg is fertilised, hormonal changes are different, and therefore the menstrual cycle doesn't continue in its normal form.

So time for a quick check: The two processes that hormones control in the menstrual cycle are what? So we've got two there.

So pause while you decide and you write this down, and then we'll come back and check that you've got it right.

Okay, so the two processes that hormones control in the menstrual cycle are menstruation and ovulation.

So if you've got those right, they're well done.

So another check for you: Put these steps in the right order to show what happens in the menstrual cycle.

So you've got: Uterus lining continues to thicken as the egg travels down the fallopian tube.

Uterus lining breaks down and menstruation takes place.

Uterus lining reforms and thickens and an egg cell is released on day 14.

And uterus lining is maintained ready for a fertilised egg, so put those statements in order.

Okay, let's see if we've got this order correct.

So number one then, uterus lining breaks down and menstruation takes place.

Number two, the uterus lining reforms and thickens as an egg cell is released on day 14.

Number three, uterus lining continues to thicken as the egg travels down the fallopian tube.

So therefore finally, the uterus lining is maintained ready for a fertilised egg.

So if you've got those in the right order, then well done.

So follicle stimulating hormone, or FSH, is released from the pituitary gland.

Now, sometimes I remember in the cycle that F is for first.

So FSH is the hormone that is released first from the pituitary gland at the start of the cycle.

And it travels in the blood as hormones do, carried in the blood plasma, down to the ovaries.

The reason it will work on the ovaries is 'cause the cells of the ovaries will have specific receptors on their surface that are complimentary to this FSH hormone.

And we can see there that it's gonna travel all the way down to those ovaries.

And in those ovaries, it's going to cause a sack that has an egg inside to develop.

Now that am-sac is called a follicle.

And in this image here, you can see that we've got those eggs inside follicles.

But once FSH comes down, it causes one of those follicles to mature, so to get bigger.

So FSH causes the follicles containing an egg to mature and it stimulates it to secrete oestrogen.

Okay, so then the ovaries will secrete oestrogen.

So have a little look at this image here.

So we've got the egg inside the follicle that's underdeveloped to start with.

Then FSH will act on it.

The follicle will mature with the egg inside it over time.

And during this process, the ovaries will release oestrogen.

So what does the oestrogen do? So the release of oestrogen from the ovaries.

So that causes the thickening of the uterus lining 'cause we know that that egg is on its way now.

So therefore the uterus lining needs to be thickened, so that's what oestrogen does.

It also causes the pituitary gland to release LH.

So we're gonna talk about what LH does in a little while.

And it inhibits the release of FSH from the pituitary gland.

Now the reason for that is because you've already stimulated a follicle to mature.

So you've got an egg that's going to be ready for ovulation.

So therefore you don't want another egg to mature during this cycle.

So that's why you're going to inhibit FSH from being released from the pituitary glands.

So we can see that these are the two effects of oestrogen.

One is on the uterus, on the thickening of the lining, and one is back to the pituitary gland, and then that's gonna cause the release of LH.

So then the LH now travels in the blood to the ovaries where it causes the mature follicle to release the egg.

So the FSH cause the follicle to mature it then prevented more FSH from being released from the pituitary gland.

It caused LH to be released, and now this LH has moved down, and it has caused ovulation, so it's caused that egg to be released.

Again, I sometimes remember the L as in last hormone from the pituitary gland.

So I remember the FSH is first and LH is last, but it causes that egg to be released.

The oestrogen, we've already said, causes the thickening of the uterus and it also causes the release of LH, and LH causes ovulation.

So time for a quick check, lots of information there.

So put these images in the correct order to show the effect of hormones in the ovary.

So the correct order.

So pause the video while you decide, and then I'll come back and give you some feedback.

Okay, let's see how we've got on then.

So first off, the first one in order will be the FSH is first and it causes that follicle to be matured.

The second one is that then that ovary will release oestrogen.

And then the third one is that the LH will then cause the egg to be released from the follicle.

So if you got those the right way round, then well done.

So now I'd like you to put these events in order, starting with FSH.

So once you've decided the order, come back, and we'll see if you've got it right.

Okay, let's see if we've got the order right then.

So first thing to happen is the FSH is released from the pituitary gland and it travels to the ovaries.

The second is that a follicle matures and oestrogen is being released.

The third is that oestrogen causes the uterus lining to thicken and LH to be released.

And finally, the last one, the fourth one, LH causes ovulation.

So time for a practise test now.

So I've done a diagram for you here, and it's just got a model of a head there with a gland there in the brain, and it's got the uterus and ovaries and fallopian tubes, vagina on there.

So first of all, I would like you to label the diagram with the glands and the hormones that are being released.

I'd like to show the movement of the hormones using different colour arrows, and then write a description of the hormones' action.

So quite a few things to do.

So labelling it first with the glands and the hormones, show the direction of the movement of those hormones in different colours, and then write a description of what the hormones do.

So pause the video, and then I'll show you a model when you come back.

Okay then, so let's start with the pituitary gland labelled at the top there and the ovary labelled at the bottom.

Those are our glands labelled.

Then we've got FSH on this first arrow and it causes an egg follicle to mature, and oestrogen to be be released.

Then our next coloured arrow is oestrogen, which moves up to the pituitary gland and causes LH to be released.

And then we've got also on there, sorry, our oestrogen in the same colour, which causes the uterus lining to build up and it inhibits the release of FSH.

And then on the final coloured arrow, we've got that the LH causes the egg to be released, which is ovulation.

So you might have done it in a slightly different structure, but you need to have all of that information and those hormone names and glands on there.

And if you've done that, well done.

So it's time to move on to the second part of today's lesson.

So LH and FSH also cause the mature follicle to break down and to release the hormone, progesterone.

So this is another hormone name for us here.

So FSH causes the follicle to mature, and LH causes the ovulation and maturation of the follicle.

And then the mature follicle will release progesterone.

So progesterone maintains the uterus lining and it prepares it for implantation of a fertilised egg.

So progesterone prepares the uterus lining there in that image.

So we had that oestrogen at the start causes the uterus lining to develop, but then progesterone allows it to thicken and prepares it ready for that fertilised egg, because the egg has now left the follicle, so it is on its way to the uterus.

It also stops the secretion of FSH and LH from the pituitary gland.

So both of those hormones have now stopped from being secreted.

So we've got that on that diagram there.

So we can see on our diagram the two roles of progesterone.

So when the follicle breaks down, so to start with, the follicle is making the progesterone, but when that follicle eventually breaks down, then the progesterone levels will drop.

So it's maintaining the uterus lining while it's being made.

But as the follicle breaks down, there's less progesterone.

So therefore, the uterus lining is no longer needed, and so menstruation begins.

And you can see again in this image, when you've put your progesterone there, you've got the uterus lining being maintained.

But as the follicle starts to break down, the progesterone levels decrease and therefore menstruation is going to start to take place.

So time for a quick check.

So progesterone maintains the uterus lining, true or false? Now, once you've decided whether that is a true or false, you need to decide which of these statements best justifies is it: It prepares the uterus lining for the implantation of a fertilised egg? Or is it: It causes the release of an egg from the follicle? Okay, so pause while you decide and then we'll come back and see if you've got it right.

Okay, so progesterone maintains the uterus lining, this is true.

And the statement that best justifies that true answer is that it prepares the uterus lining for the implantation of a fertilised egg.

So if you got that right, then well done.

Okay, another check activity.

So we've got some images here.

I'd like you to put the images in the correct order.

So we've got ovulation occurs, menstruation occurs, and mature follicle releases progesterone.

So pause the video while you do that and then we'll check that you've got the right order after.

Okay then, so the correct order is as follows: Number one is that ovulation occurs.

Number two is that a mature follicle releases progesterone.

And number three is eventually menstruation occurs.

Obviously, there's lots of processes in between, but those are the three that we were looking at in this chat.

So let's continue with progesterone.

So days 0 to 5, progesterone levels decrease.

So therefore, menstruation will take place 'cause progesterone maintains that room lining.

And then we've got day 6 to 14 where FSH causes a follicle to mature and oestrogen to be released.

Oestrogen then causes the thickening of the uterus lining and causes LH to be secreted.

On day 14, LH causes ovulation.

On days 15 to 19, progesterone is maintaining the lining.

Then days 20 to 28, progesterone continues to maintain the uterus lining, and it prevents the secretion of FSH and LH.

And then we return to the start where the progesterone levels decrease and menstruation takes place.

So we've circled back to where we were at the start of the lesson, looking at the menstrual cycle and what happens at each stage.

But what we've done this time is we've added all of the hormones in there so that we can see what's controlling the processes at each of those points in the cycle.

So the changes are the levels of different hormones, and those different hormones control the menstrual cycle.

So we know what they cause and we know when they stop, and we know that ovulation occurs around day 14.

So then we can then refer this to a graph.

So you can see on the graph how the levels of the different hormones are changing.

So we've got those increasing levels of FSH to start with, and then they start to go down and oestrogen goes up.

We can see there's little peaks of FSH and LH at about day 14, which is when ovulation takes place.

And then we can see after ovulation takes place that our LH and our FSH levels go down as the progesterone levels come up.

And then the progesterone levels remain high while the uterus lining is thick, and then they drop back down ready for menstruation to start.

So you can see how all of those things relate to each other in that image.

So time for a check: Progesterone levels rise after day what, and this is when what occurs? So I'll put the graph there for you to refer to.

So how would you fill in those two gaps? So pause the video while you decide, and then we'll check if you've got it right.

Okay, so progesterone levels rise after day 14.

And this is because this is when ovulation occurs.

So if you've got those two right, then well done.

Let's try this one now.

So oestrogen levels rise after what levels? Okay, so pause the video while you decide, and then we'll come back and see if you've got it right.

So oestrogen levels rise after FSH levels.

So again, if you've got that right, then well done.

So time for a practise test now.

So what I would like you to do is to use the image to explain the effect of the four hormones on the following processes, follicle maturation, ovulation, uterus thickening, and menstruation.

I'd like you to include timings which indicate the monthly cycle.

So a little bit of writing for you to do here.

So pause the video while you do that, and then we'll come back, and we'll have a look at model answer.

Okay, so let's give you some feedback on that and practise task then.

So in days 0 to 5, progesterone levels released from the follicle decrease, and menstruation takes place.

On day 6 to 14, FSH is released from the pituitary gland, causing a follicle to mature and oestrogen to be released from the ovary.

And then oestrogen causes the thickening of the uterus lining, and that causes LH to be secreted from the pituitary gland, and it also inhibits the secretion of FSH.

And we continue.

On day 14, LH causes an egg cell to be released and the follicle to produce progesterone.

From days 15 to 19, progesterone maintains the uterus lining and it stops the secretion of LH and FSH from the pituitary gland.

And finally, during the days 20 to 28, progesterone maintains the uterus lining and prevents the secretion of FSH.

Okay, so there's lots of information there in that final task.

I hope that you managed to get the detail in.

If not, maybe you can go back and correct your answer to make sure that you've got everything that you need in there.

So now it brings us to the summary of today's lesson, which is "Hormone control of the menstrual cycle." So FSH is released from the pituitary gland and it causes follicle maturation and secretion of oestrogen by the ovaries.

Oestrogen causes the thickening of the uterus wall and the secretion of LH by the pituitary gland, and it inhibits the secretion of FSH.

LH causes an egg to be released from the mature follicle during the process of ovulation.

FSH and LH cause mature follicle to break down and secrete progesterone.

Progesterone prepares the uterus for the implantation of a fertilised egg, by maintaining the lining, and it stops the secretion of LH and FSH by the pituitary gland.

As the mature follicle breaks down, it releases less progesterone, which causes menstruation.

So well done for your work in today's lesson, and I'll see you soon.