Hello, and welcome to this lesson from the unit, "Reproduction in Humans".

The title of today's lesson is "The Human Menstrual Cycle", and we're gonna look at the importance of the human menstrual cycle, what it is, and the stages that take place as we go through it.

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

So by the end of today's lesson, you should be able to explain how the menstrual cycle prepares adult human females for sexual reproduction.

And as with all of our lessons, we've got some keyword to look out for today, and our keywords are ovaries and ovulation, menstruation, fallopian tubes, and hormones.

So I'm gonna put the definition slide up, so you might want to pause the video for a few seconds, and then you can write those down, but we will be going through each of them through the lesson today.

So our lesson today is in two parts.

The first is the role of the menstrual cycle.

So why do we have it, why it's useful, and the second part of the lesson is the actual cycle itself.

So what are the stages of that cycle and what happens? So we're gonna start with the first part of our lesson, which is the role of the menstrual cycle.

So the menstrual cycle involves processes that take place in the human female reproductive system, and here's a reminder of what that looks like.

Now, you should have learned about this reproductive system before.

So can you recall any of the key parts, the key organs of this system? Maybe you could discuss it with the person next to you, and I'll just pause for a few seconds and then we'll see what you can recall.

Okay, let's see what you've got then.

So for, to start with, we have got the ovaries, and then we've got the fallopian tubes.

So there's two of those, one each side.

And then we've got the uterus and the cervix, which is the opening to the uterus, so that's usually pretty sealed up, and then we've got the vagina.

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

But if you got most of them right, that's also really good.

Okay, so the menstrual cycle.

So the menstrual cycle is approximately 28 day cycle.

Now we say approximately because it is different depending on different women.

So it can be quite short, so it could be down to 24 days, and it can be up to 35 days, and sometimes the menstrual cycle isn't exactly the same for one woman.

So one month it might be 28 days, and another time it might be 32, 33 days, so it's quite variable.

We usually say it's about 28 days approximately, and the menstrual cycle prepares an adult female's body for pregnancy.

So here we go, this is the uterus being prepared, ready for a fertilised egg cell.

And what happens within the uterus is it makes the right conditions in order that a fertilised egg may develop and might grow, and then offspring will be formed.

And that's a foetus that's growing inside a uterus, and you will have learned about the stages of foetus development from zygote, to embryo, to foetus in previous lessons.

So hormones are chemical messengers in the body, so they control lots of processes within the body.

We've talked about sex hormones before, and those are the ones that control puberty.

So they also control the menstrual cycle, and these hormones are released by the brain and the ovaries because the ovaries are glands so they release hormones.

The hormone levels change during the cycle in order to control the process.

So they go up and down to make the changes that take place each month, and then they cycle back around and make those same changes every month.

So when we say month, around 28 days.

Okay, so let's have a quick check then.

So I would like you to complete these sentences.

So the menstrual cycle happens in adult human what> Each cycle lasts how long? The cycle is controlled by chemical messengers called what? So pause the video.

Okay, so let's see how you got them.

So the menstrual cycle happens in adult females, each cycle lasts approximately 28 days, and the cycle is controlled by chemical messengers called hormones.

So if you've got all three of those right, then well done.

Okay, let's move on.

So the menstrual cycle begins at puberty.

Now the start of puberty is different for each individual again, but in most females, it starts between the ages of eight and 14, and the menopause is when the menstrual cycle stops, and that occurs around the age 50.

But again, it's quite variable 'cause individuals are all different, and so that sometimes it can be quite early and sometimes it can be quite late.

While the menstrual cycle occurs, reproduction can take place.

So pregnancy can happen, and offspring can be formed.

So if we have a look at this picture here, we can see that puberty starts at childhood, and continues through being a teenager until you get to be an adult.

And at some point during puberty, the menstrual cycle occurs, and therefore, and it continues through adulthood until you get to the menopause, and that's when the menstrual cycle stops.

So the menstrual cycle stops during pregnancy.

So it starts at some point during puberty, and then it continues through adulthood.

But then when a woman becomes pregnant, the menstrual cycle stops in order that a pregnancy can be maintained because the hormone levels will need to be different during pregnancy, and the cycle stops at that point.

And then after pregnancy, at some point after childbirth, not usually immediately, the cycle continues, okay? And then it stops at the menopause.

After the menopause, the cycle stops forever, and at that point, it is not possible a woman to have a baby.

Okay, so it's time for a quick check now.

So what I would like you to do is to select the stages of life when the menstrual cycle does not take place.

So childhood, adulthood, pregnancy, or after menopause.

So if you just pause the video, and then we'll come back and see how you've got on.

Okay, let's see how you've got on with this one then.

So select the stages of life where the menstrual cycle does not take place.

So the correct answer is pregnancy and after menopause.

It begins in childhood when puberty starts, and it continues into adulthood.

So the menstrual cycle can take place in either of those stages, but it is paused during pregnancy.

So it stops for a while and starts again after pregnancy, and then it stops completely after the menopause so the menstrual cycle will not take place again.

So if you've got those right, then well done, and time to move on to our practise task.

So some pupils are discussing the importance of learning about the menstrual cycle, and Aisha says it's important to learn about why our bodies change through puberty.

, and Jacob says it's important to know how reproduction takes place.

So Aisha and Jacob have both given good reasons for learning about the menstrual cycle.

So what I would like you to do is write down the key facts that you think that they should know about the menstrual cycle using the information that you've learned in the previous slides.

Okay, if you pause the video while you do this, then we'll come back and we'll see which key facts that you have got.

Okay, so we said that Aisha and Jacob needs some key facts in order to support their good reasons for learning the menstrual cycle.

So these are the key facts that you should have.

So the changes occur in the female reproductive system.

Ovaries release hormones, the hormone level cycle through 28 days on average, and this is in preparation for reproduction, and this allows the uterus to provide the right conditions for a foetus to develop and grow.

So hopefully, you got those as key facts.

You might have put 'em in a different order, and that's fine, but those are the ideas that we need to move forward.

So well done if you did that.

So let's move on to the second part of our lesson, which is the menstrual cycle, and we're going to be looking at the different stages of menstrual cycle, and roughly how long each one lasts.

Let's look at the menstrual cycle.

First of all, a general overview.

So during each cycle, the lining of the uterus thickens to provide the right conditions to receive a fertilised egg cell, also called a zygote.

So you can see in this picture where the uterus lining thickens there on the inside.

The other thing that occurs is that an egg cell is released from the ovary.

So either ovary, so each cycle, one ovary or the other will release an egg cell, and that process is called ovulation.

If the egg cell is not fertilised when it reaches the uterus, then the uterus lining will fall away in a process called menstruation.

So as you might imagine, most eggs are not fertilised because if a woman can produce an egg almost every month, they don't have that many babies in their lifetime.

So most of the time, those egg cells are not fertilised.

So therefore, the eggs will pass out along with the womb lining, and this is sometimes called.

So the egg cells will pass out along with the lining of the uterus, and this is sometimes called a period, and this is where a female will lose two to seven teaspoons of blood per cycle.

So this blood doesn't all come out in one go.

It comes out over a number of days, and it is called menstrual blood, and it passes down through the cervix, which is the opening to the uterus, and down through the vagina, and out of the body.

So the processes of the menstrual cycle all last a number of days.

Now these the number of days that each stage takes can vary from from person to person, from woman to woman.

But overall, all of those stages together take on average 28 days.

So we're gonna have a look at each stage in a little bit more detail.

So first of all, we've got days naught to five.

Now, because it's a cycle, we don't necessarily need to start on day zero, but we do because this is the time when it's most clear that there's a start of a new cycle, which is when the period happens or menstruation happens.

So on days naught to five, the uterus lining breaks down and menstruation takes place.

So that's the stage of having a period.

And then on days six to 14, that uterus lining starts to build up again, and then on day 14, the ovary will release an egg cell in a process called ovulation.

Now it's not always day 14.

As we said, these stages can vary in length, so the egg cell could be released a few days earlier or a few days later than that.

In the next stage, the uterus lining continues to thicken as the egg cell continues on its journey down the fallopian tube.

Now in the fallopian tube, this is where fertilisation can take place.

So this is where a sperm can meet the egg, and they can fuse together.

And at this stage, we're still preparing the uterus in case that egg does become fertilised in the fallopian tube.

And then on days 20 to 28, the uterus lining is maintained in case that egg cell is fertilised and has become a zygote.

And if not, then the egg cell will pass out through the cervix and through the vagina, and the uterus lining will start to break down again, and then the whole cycle begins again.

So time for a quick check.

So starting with menstruation, can you put these images in the correct order to show the menstrual cycle? Okay, let's see how you did then.

So starting with menstruation, so that is C, number one.

And then we would move to building that lining back up again, which is D.

And then number three, we would go to B, and then finally, we would go to A, okay? That fertilised or non fertilised egg passing down into the uterus.

Okay, another check for you now.

Could you please put these statements in the correct order to describe the menstrual cycle? So the stages are ovulation occurs as an egg is released from the ovary, the uterus lining reforms and thickens, firstly, menstruation occurs as the uterus lining breaks down, and uterus lining is maintained to prepare for a fertilised egg.

So could you put those in order, please? Okay, let's have a look at how you did with those then.

So a little bit of a clue there.

Number one was firstly, menstruation occurs as the uterus lining breaks down, and then the next one is the uterus lining reforms and thickens, and then the next one is the ovulation occurs as an egg is released from the ovary, and then finally, the uterus lining is maintained to prepare for a fertilised egg.

So we've got a confidence grid now for you to have a go at.

So for each of the statements below, I want you to decide whether you think they're correct or incorrect, and then how certain you are of that.

So either you're sure that it's correct, or you think it's correct, or you're sure it's incorrect, or you think it's incorrect.

So repeat that for each of the statements below, and then we'll check back and see how you got on.

Okay, let's see then.

So the first one, menstruation always lasts five days.

This is incorrect, okay? Because it's different depending on the individuals.

The next one, a female menstruates because the lining of the uterus breaks down.

That one is correct.

The next one, the length of the menstrual cycle is always the same.

That is incorrect.

Again, it depends on the individual.

And the last one, females lose a lot of blood during menstruation.

This is incorrect.

It's five to seven teaspoons, so it's not a lot.

Okay, so your next practise task below are diagrams of the stages of the menstrual cycle in the correct order.

But what I would like you to do is write a description for each diagram to make it clear what is happening during that stage of the menstrual cycle.

So using the knowledge that you've learned in this lesson, I'd like you to detail what is happening at each stage.

So when you've finished, let's check back and we'll see how you've got 'em.

Okay then, let's see how you got on.

So these are the pictures, so put 'em in little boxes.

You might have done them as a comic strip, or just pictures in your books, but the description should be as follows.

So first stage, menstruation occurs as the uterus lining breaks down.

The second one, the uterus lining reforms and thickens.

The third one is that an egg travels down the fallopian tube and the uterus lining thickens.

And finally, the uterus lining is maintained to prepare for a fertilised egg.

And then obviously, the cycle then begins again.

Okay, so well done if you got those correct, and well done with your work on today's lesson.

Now it's time for our summary.

So the summary of the human menstrual cycle.

The menstrual cycle involves processes that take place within the adult female reproductive system.

Adult human females have a menstrual cycle that is controlled by hormones, and prepares them for sexual reproduction.

On average, the menstrual cycle is 28 days with different stages that can vary in length.

The uterus lining thickens to create the conditions needed for the development of a fertilised egg cell.

In each cycle, an egg cell is released from an ovary into the fallopian tube in a process called ovulation.

After ovulation, the uterus lining will break down, and it leaves through the vagina in a process called menstruation.

Okay, so well done for your work in today's lesson.