Please make sure to [subscribe] join the forum in group for the latest videos please visit Facebook Armando Hasudungan

In this video we will look at the hormonal regulation of the female reproductive cycle

so we will be looking at the menstrual cycle basically and

Yes, so the menstrual cycle

the Hormones of

the female is

So much more complicated the Male's

but hopefully we'll be able to understand it by the end of this video, so

[we] begin with the hypothalamus and the pituitary glands which are made up of the anterior and posterior pituitary glands

We'll be focusing on the anterior pituitary gland the hypothalamus regulates hormones released by the anterior pituitary

through the portal blood here in

The female reproductive system the hypothalamus produces a hormone called gonadotropin-releasing hormone

which will travel here to the anterior pituitary via the portal blood and

It will cause the cells in the anterior pituitary gland to produce two important hormones

known as

FSH, follicle stimulating Hormone and LH luteinizing hormone

Please note that in males this same process also occurs Males also produce

Gonadotropin releasing hormone which will

Cause the anterior pituitary to release

Luteinizing hormone and follicle stimulating hormone, so what will these hormones do in the female body?

Well these hormones will travel to the female ovaries where the female eggs are produced

So let's just recap quickly. What the ovary is and where it is. So here. We have the uterus and

the Ovaries

Which connects to the Uterus via the Fallopian Tube essentially

But it's now known as a uterine tube so we [will] focus on this over here, so let's zoom in

so here is the ovary and

it has blood vessels and

This and it's through these capillaries these blood vessels that the hormones can enter

Now in each ovary there are follicles

Women have many many follicles in the ovaries and each month only some will begin to mature

But only one will ovulate and become essentially will ovulate and produce an egg

Now let's just say it's the beginning of the menstrual cycle. So just after female has shed her uterine wall just had the period

now within the ovaries females have many many many primordial follicles and

Each month only some of these primordial follicles will mature

Into primary Follicles, and they will keep maturing but only one will ovulate

So here. I'm drawing one primary follicle, and it's the beginning of the menstrual cycle

Before we continue on let's look at the let's look at the changes [of] the hormone concentrations

That come from the brain by looking at a graph

so

here we have a y-Axis which shows the concentration of the hormones in blood and

On the [x-axis] is a duration of the female menstrual cycle which normally goes for about 28 days

So the dotted line in the middle is 14 days. Which is halfway

Now just to simplify things even more the menstrual cycle can be divided into two phases

the first 14 days is known as the follicular Phase and

the Last 14 days

Is known as the luteal phase and this is important to keep in mind, so the first is the follicular Phase

II is the luteal Phase

Now initially in the beginning of the menstrual cycle there is an increase in Gonadotropin releasing hormone secreted by the hypothalamus

because it's the start of the menstrual cycle and

this should cause a steady increase in Follicles stimulating hormone and

luteinizing hormone

but instead we see a

Increase and then a slow

Dropping level of follicle stimulating hormone, and we have a steady level of luteinizing hormone

Why is this?

Well the reason is actually quite complicated, but just hold on to that thought and hopefully it'll make sense

So let's go back to the ovary

So follicle stimulating hormone

Will initially rises remember?

Because the follicular phase is the first phase of the menstrual cycle

Follicle stimulating hormone will enter the ovaries and what they will essentially do is stimulate it will stimulate

follicle Maturation of these

primary Follicles and

so some of these primary follicles will mature into

A secondary follicle, I'm only drawing one secondary follicle for simplicity

While these follicles are maturing they produce another hormone called Estrogen

Now Estrogen has many effects in

the first ten days of the menstrual cycle

So in the beginning estrogen has a negative feedback on the pituitary gland inhibiting the release of luteinizing hormone

To put it simply at low concentrations estrogen inhibits luteinizing hormone secretion from the anterior pituitary

And that is why we only see a steady level of luteinizing hormone in the blood

Because even though gonadotropin-releasing hormone

from the hypothalamus is stimulating the release of luteinizing hormone at

low

concentrations estrogen will inhibit

luteinizing hormone release

Another fact is that follicle stimulating hormone is secreted

primarily in response to Low Estrogen

concentrations, so when Estrogen levels rise

Follicle stimulating hormone levels will fall and that is why we see in the graph a steady drop in

Follicle stimulating hormone because there's a increase in Estrogen levels from the follicles

So let's draw another graph and see the concentrations of the hormones produced by the ovaries during the menstrual cycle

Which goes on for 28 days

So as the follicle matures they will produce more estrogen

which as I mentioned at low concentrations estrogen will inhibit the secretion of luteinizing, hormone and

Also the increase in estrogen concentrations will cause a decrease in Follicle stimulating hormone secretion

Estrogen is an important hormone

Especially for females because Estrogen is basically males equivalent of testosterone, Estrogen

Peripheral effects include stimulating bone and muscle Growth it stimulates endometrial growth

Maintains female Secondary characteristics and maintains a female the glands the breasts amongst many other things

So just to draw this graph up to

Ten days of the Menstrual cycle. We see a steady a steady

low concentration of luteinizing Hormone due to the inhibitory effects of estrogen remember in the first ten days and

We also see a steady drop of follicle stimulating hormone due to the increase in estrogen levels as well. Which has a negative feedback

So what happens after 10 days?

well after 10 days estrogen levels will continue to rise as the follicles mature in the ovaries and

After 10 days as estrogen levels rise. It will have a positive Feedback and

It will stimulate the release of luteinizing hormone

so at low concentrations estrogen will inhibit luteinizing hormone secretion however at

High concentrations, Estrogen will stimulate luteinizing hormone secretion

Now things are changing

the increase in gonadotropin releasing hormone and estrogen will stimulate

then luteinizing Hormone secretion

And you see this massive spike in luteinizing hormone concentration

It's this massive

luteinizing Hormone concentration that will trigger

ovulation of the Most Mature Follicle in the ovary

The ovulation of the follicle will release what we know as the female egg the oocyte

or Oocyte

After ovulation the luteinizing hormone levels will drop back down

gonadotropin releasing Hormone will slowly drop as well

follicle stimulating hormone also had a small spike as a side effect of the surge of luteinizing hormone release

so luteinizing Hormone triggers ovulation and

oocyte is released after

The Follicle ovulates the follicle will turn into a corpus luteum which is a dead follicle, basically

Now that is why the first 14 days of the menstrual [cycle] is called the follicular Phase

Because it all has [to] do with the follicles and its maturation and the last 14 days is known as the luteal phase

Because we have the formation of the corpus luteum

The corpus luteum will essentially slowly degrade

However it also has a purpose it in that it secretes hormones. It secretes three hormones estrogen again

inhibin and Progesterone

So what we see in the concentration levels of these Ovarian hormones

Estrogen will increase until

ovulation and then drop slightly

Inhibin was not present until after ovulation then it begins to increase thanks to the corpus luteum

Progesterone levels will were low until after ovulation during the luteal phase

so at

21 days of the female reproductive cycle progesterone is increasing inhibin is increasing and

Estrogen is still detectable and all these hormones are all produced. Thanks to the corpus luteum

So what do these hormones do?

Well inhibin has a negative feedback

And it will essentially inhibit the secretion of follicle stimulating hormone because we are at the luteal Phase

We don't need any more follicles to mature just yet

So that is why inhibin is preventing follicle stimulating hormone release to prevent follicle maturation

So here. I wrote as the secondary corpus luteum develops inhibiting secretion will suppress follicle stimulating hormone

release

Progesterone is the most

important Hormone in

The Luteal phase and has many functions [one] of which is having a negative effect on the hypothalamus

inhibiting the secretion of gonadotropin releasing hormone

Now after ovulation during the luteal phase

The progesterone levels will increase slowly and the estrogen levels will decrease

Slowly kind of and this will suppress gonadotropin releasing hormone release

and

So progesterone will inhibit gonadotropin releasing hormone release

Which will also [effect] the release of luteinizing hormone and follicle follicular stimulating hormone?

So during the luteal phase as progesterone and inhibin increase

This will essentially cause a decrease in

gonadotropin releasing Hormone, luteinizing Hormone and follicular stimulating hormone

But the main effect of progesterone is that it will stimulate endometrial growth

the endometrial lining is the lining of the uterus which will shed each month or

Or the endometrium is where the egg?

Will implant if it's fertilized

by sperm

okay, let's just say there was no fertilization because this is just a normal menstrual cycle and

Of course all good things have to come to an end the corpus luteum in the ovary will degenerate

allowing a new set of Follicles to mature

So as the corpus luteum degenerates all these hormones that are that were produced by the corpus luteum

the estrogen, inhibin and progesterone, they will decrease like so

so when the corpus luteum degenerates

Progesterone will Decrease and

this will mean that progesterone cannot inhibit gonadotropin releasing hormone release and

So gonadotropin releasing hormone levels will increase and this will allow a new menstrual cycle to occur

also

because of the decrease in Progesterone and estrogen in part

means that these hormones cannot maintain the endometrium the endometrial lining in the uterus and

so the endometrium will shed and this is known as the period and

After the endometrial lining sheds this allows a new cycle to occur and though

And then you see a increase in gonadotropin releasing hormone again and the cycle continues

Hope you enjoy this video. Thank you