Female Reproductive Cycle | Menstrual Cycle

Summary

This video explains the female reproductive cycle, focusing on the menstrual phases. It details the roles of estrogen and progesterone in the cycle, including menstruation (shedding of the endometrial lining), the proliferative phase (regeneration of the endometrium and arteries), and the secretory phase (preparing the uterus for a potential pregnancy). The video covers the hormonal changes, uterine anatomy, and how these hormones affect the uterine lining, cervical mucus, and blood flow. It also discusses what happens if fertilization occurs, as well as the effects if it doesn’t, including the formation of the corpus albicans.

Takeaways

• 🔄 The menstrual cycle has three phases: menstruation, proliferative, and secretory.
• 🩸 Menstruation involves shedding the stratum functionalis, a layer of the endometrium, along with blood from the spiral arteries.
• 🌱 The proliferative phase, days 6-14, regenerates the stratum functionalis and spiral arteries, driven by estrogen.
• 🧬 Estrogen also leads to the creation of uterine glands and thin cervical mucus, aiding sperm movement toward the egg.
• 🚼 Around day 14, ovulation occurs, releasing an oocyte for potential fertilization.
• 🧪 The secretory phase (days 15-28) is driven by progesterone, which thickens the stratum functionalis and enhances blood supply via spiral arteries.
• 🥣 Progesterone stimulates uterine glands to secrete a nutrient-rich fluid to nourish a potential embryo.
• 🛑 If fertilization occurs, human chorionic gonadotropin (hCG) from the embryo maintains progesterone production.
• ⚠️ If no fertilization occurs, the corpus luteum dies, progesterone drops, spiral arteries weaken, and menstruation begins again.
• 🧫 The cycle restarts if no embryo forms, and the corpus luteum turns into scar tissue called the corpus albicans.

Q & A

What are the three phases of the menstrual cycle?

The three phases of the menstrual cycle are menstruation, the proliferative phase, and the secretory phase.

What happens during the menstruation phase?

During the menstruation phase, the stratum functionalis (the upper layer of the endometrium) is shed, resulting in blood loss from the spiral and coiled arteries.

What are the two layers of the endometrium and their functions?

The two layers of the endometrium are the stratum functionalis, which is shed during menstruation, and the stratum basalis, which remains and regenerates the stratum functionalis during the next cycle.

What role does estrogen play in the proliferative phase?

During the proliferative phase, estrogen helps regenerate the stratum functionalis, stimulates the growth of spiral and coiled arteries (angiogenesis), and starts the formation of uterine glands.

Why is thin cervical mucus important during the proliferative phase?

Thin cervical mucus is important because it allows sperm to pass more easily through the cervix, facilitating fertilization during ovulation.

What happens during the secretory phase?

In the secretory phase, progesterone thickens the stratum functionalis, promotes the growth of spiral and coiled arteries, stimulates uterine glands to produce nutrient-rich fluids, and forms a thick cervical mucus plug to protect the uterus.

What hormone drives the secretory phase, and where is it produced?

Progesterone drives the secretory phase, and it is produced by the corpus luteum in the ovary.

What happens if fertilization does not occur by the end of the secretory phase?

If fertilization does not occur, progesterone levels drop, the spiral arteries spasm and rupture, leading to the shedding of the stratum functionalis, which results in menstruation.

What is the corpus luteum, and what happens to it if fertilization does not occur?

The corpus luteum is a hormone-producing structure formed from the Graafian follicle after ovulation. If fertilization does not occur, it degenerates into the corpus albicans, a scar-like tissue, and stops producing progesterone.

What is the function of human chorionic gonadotropin (hCG) if fertilization occurs?

If fertilization occurs, the embryo releases hCG, which signals the corpus luteum to continue producing progesterone until the placenta is developed around the 12th week of pregnancy.

Outlines

00:00

🧠 Introduction to Female Reproductive Cycle Phases

The speaker introduces the video as a continuation of the female reproductive cycle, referencing the ovulatory cycle. Progesterone and estrogen production by the corpus luteum are discussed, setting the stage for explaining the three phases of the menstrual cycle: menstruation, proliferative phase, and secretory phase. The endometrium's two layers—stratum functionalis and stratum basalis—are introduced, focusing on how the stratum functionalis sheds during menstruation, along with blood from spiral and coiled arteries.

05:01

🌱 Proliferative Phase and Endometrial Regeneration

The proliferative phase is described, highlighting how the stratum functionalis and spiral arteries regenerate after menstruation (days 6–14). Estrogen plays a crucial role in this process by promoting endometrial regrowth and angiogenesis (formation of new blood vessels). Additionally, uterine glands begin forming, though they are not yet secreting fluids. Estrogen also causes the cervical glands to produce thin mucus to facilitate sperm movement during ovulation, helping in sperm capacitation.

10:02

🌸 Secretory Phase and the Role of Progesterone

In the secretory phase (days 15–28), progesterone takes over as the dominant hormone, thickening the stratum functionalis and increasing the number of spiral arteries. Progesterone also stimulates the uterine glands to produce a nutrient-rich fluid for potential embryo nourishment. It thickens cervical mucus, forming a plug to protect a potential embryo by preventing substances or organisms from entering the uterus. This phase is essential for preparing the body for implantation if fertilization occurs.

15:02

⏳ Menstrual Cycle Recap and Potential Outcomes

The video outlines the end of the menstrual cycle, explaining that if fertilization does not occur, progesterone levels drop, causing the spiral arteries to spasm and rupture, leading to the shedding of the stratum functionalis. This results in menstruation, beginning a new cycle. If fertilization does occur, human chorionic gonadotropin (hCG) from the embryo signals the corpus luteum to continue producing progesterone until the placenta forms.

20:07

💔 Corpus Luteum Degeneration and Conclusion

If fertilization does not occur, the corpus luteum degenerates and transforms into a fibrous tissue called the corpus albicans, marking the end of its role in hormone production. The video concludes with a promise to review the entire female reproductive cycle in a subsequent video, ensuring viewers understand the complex hormonal interactions throughout the menstrual cycle.

Keywords

💡Menstruation

Menstruation refers to the shedding of the uterine lining, specifically the stratum functionalis, during the first phase of the menstrual cycle. It typically lasts for about five days and involves the loss of tissue and blood, which comes from the spiral and coiled arteries in the stratum functionalis. This is described as the 'shedding phase' in the video.

💡Endometrium

The endometrium is the inner lining of the uterus, made up of two sub-layers: the stratum functionalis and the stratum basalis. In the video, it is emphasized that the stratum functionalis is the layer that sheds during menstruation, while the stratum basalis remains to help regenerate the endometrial lining in later phases.

💡Stratum functionalis

The stratum functionalis is the top layer of the endometrium that is shed during menstruation. In the video, it is explained that this layer is lost along with blood from the spiral arteries during the menstruation phase, and it regenerates during the proliferative phase. Its role is critical in preparing the uterus for a potential pregnancy.

💡Proliferative phase

The proliferative phase is the second phase of the menstrual cycle, occurring from approximately days 6 to 14. During this phase, estrogen stimulates the regeneration of the stratum functionalis and the development of spiral arteries. The video highlights how estrogen drives this phase, leading to the rebuilding of the uterine lining.

💡Spiral and coiled arteries

These are blood vessels found in the stratum functionalis of the endometrium. The video describes how these arteries are shed along with the endometrial lining during menstruation and regenerate during the proliferative phase. Their rupturing and regrowth play a key role in both menstruation and preparation for pregnancy.

💡Estrogen

Estrogen is a hormone primarily responsible for stimulating the regeneration of the stratum functionalis during the proliferative phase. In the video, it is described as promoting the proliferation of the endometrial lining and aiding in the development of uterine glands and thin cervical mucus to help sperm reach the egg.

💡Secretory phase

The secretory phase is the final stage of the menstrual cycle, occurring from days 15 to 28. In the video, it is explained that progesterone, produced by the corpus luteum, stimulates the thickening of the endometrium and the secretion of nutrients from uterine glands, preparing the uterus for potential embryo implantation.

💡Progesterone

Progesterone is a hormone produced by the corpus luteum during the secretory phase. It thickens the stratum functionalis, promotes the formation of spiral arteries, and triggers the secretion of nutrient-rich fluids from uterine glands. In the video, it is highlighted for its role in preparing the uterus for embryo implantation.

💡Corpus luteum

The corpus luteum is a structure that forms from the Graafian follicle after ovulation and produces progesterone. As described in the video, it plays a crucial role in the secretory phase by maintaining the thickened uterine lining. If fertilization does not occur, the corpus luteum degenerates into the corpus albicans.

💡Corpus albicans

The corpus albicans is the scar tissue that forms when the corpus luteum degenerates due to a lack of fertilization. In the video, it is described as the end result of the menstrual cycle if fertilization does not occur, marking the cessation of progesterone production and the beginning of a new menstrual cycle.

Highlights

Introduction to the female reproductive cycle and its dependence on understanding the ovulatory cycle.

Explanation of progesterone and estrogen production from the corpus luteum and their role in the menstrual cycle.

Introduction of the three phases of the menstrual cycle: menstruation, proliferative phase, and secretory phase.

Detailed description of menstruation as the shedding of the stratum functionalis layer from the endometrium.

Distinction between the stratum functionalis and the stratum basalis in the uterus, with the former being shed during menstruation.

Explanation of the role of spiral and coiled arteries in the stratum functionalis, contributing to blood loss during menstruation.

Proliferative phase overview: regeneration of the stratum functionalis and spiral arteries, influenced by estrogen.

Explanation of angiogenesis and the creation of new arteries during the proliferative phase.

Role of estrogen in forming thin cervical mucus, aiding sperm movement and capacitation during ovulation.

Secretory phase discussion, focusing on the role of progesterone in thickening the endometrium and stimulating uterine glands.

Formation of a thick cervical mucus plug during the secretory phase to protect the uterus if fertilization occurs.

Impact of progesterone on maintaining stable blood vessel activity in the endometrium, preventing necrosis.

Menstruation as a result of ischemia and necrosis when progesterone levels drop, leading to the shedding of the stratum functionalis.

Role of human chorionic gonadotropin (hCG) in sustaining the corpus luteum and progesterone production during pregnancy.

Corpus luteum degeneration into corpus albicans if fertilization does not occur, marking the end of the menstrual cycle.

Transcripts

iron engineer it's in this video we're

gonna continue our discussion about the

female reproductive cycle if you guys

haven't already seen it go and watch the

ovulatory cycle first because it's

completely dependent upon being able to

do this video okay alright so now if you

guys remember we left off with

progesterone production right from the

corpus luteum and then we had estrogen

production also right so let's bring

estrogen over here so we can have them

together so over here you're gonna have

a stroke gin and progesterone now before

we actually go into what these hormones

are gonna do to the uterus let's map out

the three phases of the menstrual cycle

okay so the three phases in order first

one is going to be menstruation now the

menstruation face is the shedding face

that's how what they can actually go you

know will actually put like a little

like a thing here to kind of describe it

so this is a shedding face what do I

mean by shedding okay in here in the

uterus you have an inner lining so

there's an inner lining of the uterus

just called the endometrium okay so

again what are the two layers here

there's actually the specific layer is

called the endo metrium now the

endometrium is actually composed of two

like sub layers or strata if you will

you see this like lime green one right

there that lime green one is actually

called the stratum function Alice okay

so this green one right here is actually

called the stratum function Alice okay

it's that green layer right there this

blue layer below it is actually called

the stratum base Alex okay so one more

time endometrium is the inner lining of

the uterus which is made up of simple

columnar epithelial tissue and it

consists of two different sub layers one

is the stratum function Alice which is

this green lime layer right there and

then the

other one is the Shraddha massage which

is this actual blue layer here during

menstruation the stratum function Alice

is the one that gets shed out of the

uterus so what is actually being shed

out of the uterine lining it's actually

going to be the stratum function Alice

that's being shed okay now about how

long is the menstruation period now

again assuming that it's an average that

average is about days one to five

obviously it could change from person to

person right depending upon whether they

have that actual menstruation period or

whether they have heavy menstruation you

know men arrayed you okay now days one

through five is the period in time in

which this actual stratum function house

is being shed so now let's show that

then so what also is being broken down

oh before I do that let's actually

discuss something really quick you see

the stratum bus house right there you

see that red artery that's going through

it that's a straight artery then the one

in the stratum function Alice is

actually going to be spirally and coyly

artist let's write that down right now

so that you guys have that in your mind

so the stratum function Alice is really

really important it has these things

called the spiral and coiled arteries

okay I know it might seem insignificant

but it is extremely important that we

understand this and differentiate that

in the stratum bus Alice it consists of

straight arteries now specifically these

are branches of the yeren artery which

comes off the internal iliac artery so

these spiralling coyly arteries in these

straight arteries are going to be

arteries that are coming off of the

uterine artery which is a branch of the

internal iliac artery now whenever the

stratum functionals being shed what are

you actually losing with it the spirally

and coiled arteries that's why there's

blood being lost so not only is there

tissue loss there's also going to be

blood loss and that blood that you're

losing is the vessels those spiralling

coyly arteries but what are you keeping

those straight arteries which are

than the stratum ViSalus okay that's the

first step so that's our menstruation

phase and what was the ministrations

consisting of specifically the shedding

of the stratum function Alice with the

blood that's carried by the spiral and

coyly arteries cool now what did you see

that actually remains here - raddimus

Alice remains so this next phase is

actually called the pro literate 'iv

phase now the proliferative phase is

actually going to be whenever you're

regenerating your actual stratum

function out of the endometrium so the

proliferative phase you actually

regenerate your stratum function Alice

layer so you shat it off in the

menstruation phase and then you

regenerate it within the proliferative

phase another thing that you're going to

regenerate is you're gonna regenerate

these spirally and coyly arteries so

you're gonna regenerate this spiraled

and coiled arteries and I'm gonna

explain how this happens okay so first

off what days is the proliferative phase

actually occurring from it's occurring

approximately from about days 6 to 14

now if we come back over here for a

second - the actual follicular phase you

guys remember what days with a

follicular phase days 1 through 14 and

what was the primary hormone working in

that area FSH right what was the primary

hormone being produced estrogen so now

let's go ahead and see what this

estrogen that we produced over here what

it's actually doing in the uterus we

heard he told you what it's doing it's

regenerating the stratum function house

so let's show that what is it going to

regenerate here it's gonna regenerate

the stratum function Alice that's why

they call it the proliferative phase

because it's gonna cause proliferation

right of the endometrium

all right specifically the stratum

function what else did I say it was

gonna do it was gonna regenerate those

spirally and coyly arteries what does

that call whenever you actually make new

arteries you know that's called

angiogenesis

it's kind of a long-term autoregulation

but this is where you're making these

new spirally and coyly arteries and

again who's doing this this is actually

going to be the job of Astra j'en now

you know what else a surgeon is doing

not only is this regenerating the

straddle functionality not only is it

regenerating the spiralling coyly

arteries but you know there's also

uterine glands that we have to have

these little uterine glands that are

secreting specific fluids he's starting

the process of making these uterine

plants and these uterine glands are

gonna be really important in the next

phase that we talk about but again what

is it doing it's leading to the starting

the production of these uterine glands

they're not secreting anything they're

just making these uterine glands so

what's the next thing that they also do

up here so not only was it regenerating

the stratum function Alice and the

spiraling core the arteries but it was

also making uterine glands look what

else it does it's also really smart too

you know here this is the cervix of your

uterus there's specific glands within

the cervix of yours

you know these glands these actually

like like mucous glands look what

estrogen does to these glands it tells

these glands to start producing a mucus

but this mucus that it produces is very

thin so there's brown stuff that I'm

drawing here this is a mucus but this

mucus is very very thin mucus why is it

important to have a thin mucus because

what happens around day 14 to about do

you know day 14 or 15 the female

actually undergoes what's called

ovulation right and injects that Oh a

site out into the ampulla the fallopian

tubes

if sperms if someone's a little swimmer

decides to run up through this actual

female reproductive tract do you want it

to be blocked by a thick mucus plug no

you do not you want it to be nice and

thin and if it's thin it's gonna be

easier for it to actually move towards

the actual egg so not only do you want

it to be skin but you also wanted to

consists of very specific chemicals that

we talked about in fertilization that

helps with called capacitation of the

sperm so what is it doing here to the

cervical mucus production it's making it

thin so what

estrogen doing here also it's also

causing thin cervical mucus production

for what so that it's easier for the

sperm to move up to the egg and it also

contains chemicals that help with help

ending capacitation of the sperm

activating the sperm helping it to clean

its head right of cholesterol and local

proteins and different types of things

like that okay that's what's happening

within this proliferative phase which is

around a six through fourteen okay

and again what is it doing just to recap

again it's causing proliferation of the

actual stratum function Alice of the

endometrium it's helping the actual

angiogenic effect to make more spirally

in coyly arteries it's leading to the

production of these actual uterine

glands they're not secreting anything

just undergoing the production of them

and on top of that it's making a thin

cervical mucus that the sperm cells it's

easier to be able to get to the egg and

helps to activate the egg right I'm

sorry activate the sperm okay for

capacitation now we go into the next

part over here what is that last phase

so this last phase here it's actually

called the secretory phase now what was

the primary hormone that was involved in

the proliferative phase just so that we

can continuously recap on that what was

the primary hormone estrogen right he

was the primary hormone that was

stimulating the proliferative phase

what's the primary hormone do you think

that's going to be stimulating the

secretory phase progesterone now who was

actually synthesizing and secreting that

pedestrian let's come back remember in

the ovary we had the luteinizing hormone

convert the graafian follicle into the

corpus luteum and then it stimulated the

corpus luteum to pick progesterone that

progesterone right there that was

produced by the corpus luteum

is gonna act on the uterus what is it

gonna do here in the actual uterus it's

gonna do some of the similar effects to

what estrogen did what did estrogen do

he caused

regeneration the stratum function house

right well guess what progesterone does

he makes the actual stratum function

Alice Eve

a little bit thicker so he makes it a

little bit thicker and then on top of

that you're gonna have to have blood

supply that part of the area right there

right so what is it going to do to this

area it's gonna help to make the

spiraling corley arteries a little bit

longer right so it's gonna make more

spirally and coyly arteries guess what

else is going to do you know how those

uterine glands were synthesized and they

were made guess what the progesterone is

gonna do progesterone is actually gonna

stimulate these uterine glands to start

producing a nice type of fluid

nutrient-rich broth I know it's a heck

of a nasty word to say but that's what

it's doing it's e creating a nice

nutrient-rich broth which is rich in

glycogen which is a polysaccharide right

a polymer of glucose a lot of lipids and

a lot of specific types of proteins so

again if we look at everything it's

doing here let's map out what

progesterone is doing again the first

thing he's doing is proliferating again

so proliferating the stratum function

Alice so making it a little bit thicker

what else is he doing angiogenesis right

making those uh spirally and corley

arteries even bigger right more of them

and it's also causing the see creation

of the uterine glands within the

endometrium but it's not done at that he

has to do something else a surgeon was

causing these cervical glands to produce

a thin cervical mucus but you know if

hypothetically if a sperm that this

little swimmer would have got up there

and fertilize that egg if it fertilizes

that around day 14 technically we should

have it at least I'm uh some type of a

blastocyst that's actually going to be

implanting into the actual uterine wall

hypothetically that's not always the

case right but let's assume that there

is an embryo and planted into the

uterine wall do you want anything to

just have free access up into this

uterus no you do not so what does this

actual progesterone do it switches

the cervical mucus production by the

cervical dance and look what happens to

it he plugs this sucker up he forms a

thick thick thick cervical mucus that

plugs up the cervix why why do you want

to do that because you want to keep this

area private you don't want to have

anything have access up into this area

so you form a thick cervical mucus plug

to prevent any type of substances or any

type of organisms up into this area to

protect the actual potential embryo so

what's the last thing that it does it

also causes a thick cervical plug to be

formed okay now we're at the last part

right and what was the secretory phase

so we said that the specifically for the

actual proliferate if it was day six

through fourteen on average the

secretory phase is approximately days 15

to 28 now everyone must realize that

this is not always the case obviously

menstrual cycles change from month to

month all the time for certain people

okay on average if I was to give you

like the average generally we say that

about 28 days is like the normal range

anything that's actually 21 or below so

anything less than 21 is pathological

okay anything that's actually greater

than 40 is also pathological so on

average we like to say that the average

menstrual cycle is 28 days with give or

take a few - 21 is the lowest anything

below that is pathological and to about

40 is the top point that you want to go

one more thing if this female is

fertilized right the embryo will implant

into the wall of the uterus and it will

start producing specific types of

chemicals one of those chemicals is

called human chorionic gonadotropin and

what human chorionic gonadotropin does

it helps to be able to continuously

stimulate the

corpus luteum to make progesterone right

so if the female is not fertilized so

she doesn't have fertilization if their

embryo isn't producing those chemicals

like human chorionic gonadotropin to let

the corpus luteum know that he can start

producing progesterone right until the

placenta develops around the 12th week

right of gestation if he it doesn't get

those signals from the embryo the canoe

corpus luteum produce progesterone no so

what happens is let's say that this egg

over here is waiting for the sperm and

it gets to about you know day 26 27 28

and there's no fertilization occurring

no fertilization occurring means no

embryos implanting no embryo implanting

means no human chorionic gonadotropin no

human chorionic gonadotropin causes the

corpus luteum to not produce

progesterone why is that significant you

know these spirally and coyly arteries

that says zoom in on one let's say here

I have my spiraling core the artery it's

activity so it's activity it's normal

vasoconstriction and vasodilation

activities is completely dependent upon

the stable levels of progesterone so

progesterone is keeping the normal

contraction and relaxation of these

blood vessels it's keeping it normal but

what happens if there's no fertilization

occurring progesterone levels start

decreasing can they regulate the

contraction and relaxation of these

vessels now no so what starts happening

as a result if you don't have this

progesterone and these vessels start

undergoing spasms where they undergo

very very basal constrictive days of

relaxation phase of constriction

vasodilation so much that over time

these vessels become very very weak and

their walls become very very fragile

that what happens is eventually after

one strong basal constriction the blood

vessels dilate so much that so much

blood rushes into this area that the

capillaries in this area rupture

if the blood ruptures in this area what

starts happening so let's say that these

vessels here rupture what starts

happening then this blood starts

accumulating

in the stratum function Alice right

because these spiraling corley arteries

have ruptured

so I say here's some blood accumulates

here also and then what else over here

to write these spiraling corley arteries

also ruptured if these guys are

rupturing can the actual oxygen and

nutrients be delivered to these actual

stratum function Alice's no if the

nutrients and oxygen aren't delivered to

the stratum function Alice's they become

what's called ischemic you know what

ischemia means ischemic means it's not

getting enough oxygen supply to that

area if they become ischemic eventually

they don't get enough oxygen to where

they become necrotic in other words they

die if these tissue cells start dying

what happens they start sloughing off

it's a heck of a word I'm sorry for the

word but it's what it is it's sloughing

these actual layers off and what is it

sloughing off its sloughing off this

actual shraddha function Alice and the

blood from the ruptured spirally in

corley arteries and whenever it's lost

out through the actual vaginal canal

because what happens is eventually the

progesterone production stops right so

what happens to the cervical plug it

goes away right that's another result of

it and look what happens here look what

you lose as a result coming out of

vaginal canal they're actually gonna

have what is this this is the stratum

function Alice and what else is going to

be a part of that stratum function house

all that blood that was lost from the

spiraling coronary arteries what is this

call whenever you're shedding the inner

lining of the actual uterus menstruation

so now guess what happened the normal

menstrual cycle ended at day 28 if

fertilization didn't occur and it starts

back over on day 1 to begin the

menstruation process all over again now

like I said if fertilization does occur

then the corpus luteum continues to act

like the hormone producing structure for

progesterone until the placenta develops

around the 12th week and then it

actually dies off if the corpus luteum

doesn't I mean if their fertilization

doesn't occur then the corpus luteum

doesn't get those signals from

embryo guess what happens to the corpus

luteum the corpus luteum starts dying

and actually starts becoming scar tissue

so he starts dying and look what happens

to it it starts turning into a nice scar

and fibrous tissue scar and fibrous

fatty tissue

what is this scarred and fatty fibrous

tissue here called this structure right

here is called the corpus albicans so

it's called the corpus albicans and the

corpus albicans is again the result of

fertilization not occurring and the

corpus luteum starts dying because it

doesn't get signals from the LH or from

the human chorionic gonadotropin and

what happens it starts undergoing death

and gets converted into fibrous tissue

what is that fibrous scar tissue called

the corpus albicans okay and can this

thing produce progesterone can it

respond to LH no so then the actual

whole ovulatory cycle has to start from

the beginning also are a ninja nerds in

this video we cover a lot of information

about the female reproductive cycle I

really hope you guys enjoyed it I hope

it made sense guys what we're gonna do

in the next video is we're gonna do a

nice little overview of everything here

just to get a quick recap and make sure

that you guys truly understand all of

this

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