Female Reproductive Cycle | Ovulation & Menstrual Cycle: Overview

Summary

This video provides a comprehensive overview of the female reproductive cycle, focusing on the hormonal regulation of the ovarian and menstrual cycles. It explains the roles of FSH, LH, estrogen, and progesterone, and how these hormones control the development of follicles, ovulation, and preparation of the endometrium. The phases of the menstrual cycle, including menstruation, proliferative, and secretory phases, are discussed in detail. The video also covers key concepts such as the corpus luteum's role and the consequences of fertilization not occurring.

Takeaways

• 🧬 The female reproductive cycle involves different stages, starting with primordial follicles in the ovaries, which are present from birth and remain inactive until puberty.
• 🔬 Before puberty, these primordial follicles undergo mitosis, forming primary oocytes that are frozen in prophase I of meiosis.
• 🧠 At puberty, the hypothalamus releases Gonadotropin-Releasing Hormone (GnRH), which stimulates the anterior pituitary to produce FSH and LH, initiating follicular development.
• 🌟 Follicle-Stimulating Hormone (FSH) is responsible for converting primary follicles into secondary follicles, which eventually mature into Graafian follicles during the follicular phase (days 1-14).
• 💡 The rising estrogen levels from the Graafian follicles initially inhibit further FSH and LH release. However, a late surge in estrogen levels stimulates an LH surge, triggering ovulation around day 14.
• 💥 Ovulation releases the secondary oocyte, and the ruptured Graafian follicle transforms into the corpus luteum, producing progesterone during the luteal phase (days 15-28).
• 🔄 The menstrual cycle has three phases: menstruation (days 1-5), proliferative phase (days 6-14), and secretory phase (days 15-28). Estrogen helps regenerate the endometrial lining during the proliferative phase.
• 💧 Progesterone from the corpus luteum supports the thickening of the endometrial lining and the formation of a cervical mucus plug during the secretory phase.
• ⚠️ If fertilization does not occur, the corpus luteum degenerates, leading to a drop in progesterone levels, causing the endometrial lining to shed (menstruation).
• 📅 A typical menstrual cycle lasts about 28 days but can range from 21 to 40 days. Deviations from this range may indicate pathological conditions.

Q & A

What happens to oogonia before puberty?

Before puberty, oogonia undergo mitosis, producing many primordial follicles, which are primary oocytes surrounded by a layer of simple squamous follicular cells. These oocytes remain arrested in prophase I.

What triggers the development of a primordial follicle into a primary follicle?

The release of gonadotropin-releasing hormone (GnRH) from the hypothalamus triggers the anterior pituitary to release follicle-stimulating hormone (FSH), which stimulates the conversion of primordial follicles into primary follicles.

What are the key stages in the development of a follicle during the follicular phase?

During the follicular phase, primordial follicles develop into primary follicles, which further develop into early secondary, late secondary, and finally graafian follicles under the influence of FSH.

What role does luteinizing hormone (LH) play during the follicular phase?

Luteinizing hormone acts on the thecal cells to convert cholesterol into androgens, which are then converted into estrogens by granulosa cells. LH also contributes to the formation of the LH surge that leads to ovulation.

What is the LH surge, and why is it significant?

The LH surge occurs around day 14 of the menstrual cycle and triggers ovulation by increasing the permeability of blood vessels around the ovary and activating proteolytic enzymes that help release the oocyte from the follicle.

How does the corpus luteum form, and what is its primary function?

After ovulation, the ruptured graafian follicle transforms into the corpus luteum, which produces progesterone. Progesterone plays a critical role in preparing the endometrium for potential embryo implantation.

What are the three phases of the menstrual cycle, and what happens during each?

The three phases of the menstrual cycle are: 1. Menstrual phase (days 1-5), where the endometrium is shed. 2. Proliferative phase (days 6-14), where estrogen stimulates the regeneration of the endometrial lining. 3. Secretory phase (days 15-28), where progesterone causes further thickening of the endometrium and prepares it for embryo implantation.

What happens if fertilization does not occur after ovulation?

If fertilization does not occur, the corpus luteum degenerates into the corpus albicans, and progesterone production decreases. This leads to vasoconstriction of spiral arteries in the endometrium, causing ischemia and eventually menstruation.

What role does estrogen play in the follicular and proliferative phases?

Estrogen, produced by developing follicles, stimulates the proliferation of the endometrium during the proliferative phase and helps regenerate the stratum functionalis. It also makes cervical mucus thinner to facilitate sperm movement.

What is the significance of progesterone during the luteal phase?

Progesterone, produced by the corpus luteum, thickens the endometrium and promotes the development of spiral arteries and uterine glands. It also causes the cervical mucus to thicken, forming a plug to protect the potential embryo.

Outlines

00:00

🧠 Overview of Female Reproductive Cycle

This paragraph introduces the overall topic of the female reproductive cycle. It covers the diploid parent stem cell in the ovary, known as oogonia, which undergoes mitosis before puberty to produce primordial follicles. The discussion leads into the role of FSH and LH hormones, released from the anterior pituitary, in the maturation of follicles during the follicular phase. The paragraph highlights the process of follicular development, from primordial to Graafian follicles, and the production of estrogen, which occurs due to FSH stimulation. It also explains how estrogen levels rise and regulate the hypothalamus and pituitary in the mid-follicular phase.

05:02

📈 LH Surge and Ovulation Process

This section focuses on the role of luteinizing hormone (LH) in triggering ovulation. LH increases blood vessel permeability, leading to the release of the secondary oocyte into the fallopian tubes. LH also converts the Graafian follicle into the corpus luteum, marking the beginning of the luteal phase (days 15 to 28). During this phase, LH stimulates the corpus luteum to produce progesterone, which is essential for preparing the uterus for potential embryo implantation. This paragraph details the transition from the follicular to the luteal phase and how hormonal changes contribute to these processes.

10:04

🩸 Menstrual Cycle Phases Explained

The third paragraph explains the phases of the menstrual cycle: menstruation (days 1-5), proliferative (days 6-14), and secretory (days 15-28). During menstruation, the stratum functionalis of the endometrium is shed, along with the spiral arteries. Estrogen from the follicular phase regenerates the endometrium and stimulates cervical mucus production. Ovulation occurs around day 14, and progesterone from the corpus luteum thickens the endometrium and forms a cervical plug in the secretory phase. The paragraph also covers what happens if fertilization doesn’t occur, leading to the breakdown of the corpus luteum, the drop in progesterone, and the start of the menstrual cycle again.

📝 Cycle Variations and Conclusion

This final paragraph highlights the variability in female reproductive cycles, emphasizing that while the average cycle length is 28 days, cycles can range from 21 to 40 days without being considered pathological. Cycles shorter than 21 days or longer than 40 days are seen as abnormal. The paragraph wraps up the discussion with a recap of the main concepts, urging viewers to like, comment, and subscribe to support future educational content. The speaker expresses the hope that the video provided clarity and tied together key aspects of the female reproductive cycle.

Keywords

💡Follicular phase

The follicular phase refers to the first half of the female reproductive cycle (days 1-14) where follicle-stimulating hormone (FSH) promotes the maturation of ovarian follicles. In the video, this phase is explained in detail, emphasizing its role in preparing the primary follicle to progress through stages (primordial, primary, secondary) and ultimately leading to ovulation. Estrogen production also rises during this phase.

💡Ovulation

Ovulation is the process where a mature ovarian follicle releases an egg (oocyte) into the fallopian tube, typically around day 14 of the menstrual cycle. In the video, the narrator explains how luteinizing hormone (LH) triggers this event, which occurs after a surge of LH and increased follicular fluid pressure, allowing the oocyte to be released for potential fertilization.

💡Corpus luteum

The corpus luteum is the structure that forms from the ruptured follicle after ovulation and secretes progesterone. The video explains that LH stimulates the corpus luteum to produce progesterone during the luteal phase, which is critical for preparing the endometrium for possible embryo implantation and pregnancy. If fertilization doesn't occur, it degenerates into the corpus albicans.

💡Luteal phase

The luteal phase (days 15-28) follows ovulation, during which the corpus luteum produces progesterone to maintain the endometrial lining for a potential pregnancy. The video explains that if no embryo implants, progesterone levels fall, leading to the shedding of the uterine lining (menstruation).

💡Estrogen

Estrogen is a hormone produced mainly by the developing follicles in the ovary. It plays a key role in regulating the menstrual cycle, particularly in the follicular phase, where it helps thicken the endometrial lining and prepares the body for ovulation. The video highlights estrogen's dual feedback effects on the hypothalamus and pituitary gland, first inhibiting and then stimulating GnRH release as levels rise.

💡Progesterone

Progesterone is a hormone secreted by the corpus luteum in the second half of the menstrual cycle. It thickens the endometrial lining and promotes a supportive environment for a fertilized egg. The video explains how the drop in progesterone levels (if no pregnancy occurs) leads to the breakdown of the endometrial lining and the onset of menstruation.

💡Gonadotropin-releasing hormone (GnRH)

GnRH is a hormone produced by the hypothalamus that regulates the release of FSH and LH from the anterior pituitary. The video describes how GnRH triggers the release of these hormones, initiating follicle development and ovulation. It also explains how estrogen modulates GnRH secretion in different phases of the cycle.

💡Hypothalamus

The hypothalamus is a region of the brain responsible for regulating hormonal cycles. In the video, the hypothalamus is highlighted for its role in releasing GnRH, which then stimulates the pituitary gland to secrete FSH and LH, key hormones in the female reproductive cycle.

💡Luteinizing hormone (LH)

LH is a hormone secreted by the anterior pituitary gland, which peaks during the mid-cycle and triggers ovulation. The video explains how the 'LH surge' leads to ovulation and the transformation of the ruptured follicle into the corpus luteum, which then produces progesterone.

💡Menstruation

Menstruation is the process of shedding the endometrial lining that occurs at the beginning of the menstrual cycle if fertilization does not happen. The video explains that it marks the end of the luteal phase and the start of a new cycle. The withdrawal of progesterone leads to the breakdown of the endometrium, resulting in menstrual bleeding.

Highlights

Ovaries contain diploid parent stem cells called oogonia.

At birth, a female has all the oogonia she will ever have.

Before puberty, oogonia undergo mitosis to produce primordial follicles.

Puberty triggers the conversion of primordial follicles into primary follicles.

Follicle-stimulating hormone (FSH) is responsible for follicle development.

FSH stimulates the conversion of primary follicles into secondary and Graafian follicles.

Luteinizing hormone (LH) acts on thecal cells to produce androgens.

Estrogen levels rise during the follicular phase, days 1 to 14.

High estrogen levels inhibit the release of FSH and LH.

A surge in LH triggers ovulation and the formation of the corpus luteum.

The corpus luteum produces progesterone during the luteal phase, days 15 to 28.

The menstrual cycle consists of the menstruation, proliferative, and secretory phases.

Menstruation involves the shedding of the endometrial lining and spiraling arteries.

Estrogen regenerates the endometrial lining during the proliferative phase.

Estrogen also thins cervical mucus to facilitate sperm movement.

Progesterone thickens the endometrial lining and produces a cervical plug.

If fertilization does not occur, the corpus luteum degenerates, stopping progesterone production.

A decrease in progesterone causes the endometrial lining to shed, starting a new cycle.

Normal female reproductive cycles range from 21 to 40 days.

Transcripts

I ninja nerds in this video we're gonna

finish up and we're gonna cover the ream

female reproductive cycle and just an

overview since we've already gone over

in great detail okay so let's go ahead

and just doing mics nice little quick

recap so if you remember inside of the

ovary we have what's called a diploid

parent stem cell right that oh a go Neum

and if you remember you have all of

these at birth that you're ever gonna

have for the rest of your life now what

happens is before you hit puberty those

Ogoni UM's are undergoing mitosis right

undergoing excessive mitosis and

producing tons of these little

primordial follicles these primordial

follicles are just primary oocytes right

which have this single layer of simple

squamous like follicular cells around it

and it's still a primary oocytes so it's

frozen in prophase one and then what

happens is once you hit puberty these

primordial follicles a certain amount of

them due to the localized antigens in

the area are converting this primordial

follicle into a primary follicle right

and then if you remember what happens to

that primary follicle he gets converted

into an early secondary to a late

secondary into a graafian who triggers

that okay we got to come up the

hypothalamus if you remember in the

hypothalamus there was the arcuate

nucleus and then there was the preoptic

nucleus once you hit puberty they start

releasing gunatit rope and releasing

hormone this ganado troponin releasing

hormone stimulates the anterior

pituitary of these ganado Tropes

right to release FSH and LH now FSH what

is it gonna do it's gonna stimulate the

conversion of a primary follicle into an

early secondary and early secondary into

a late secondary and then a late

secondary into a graafian follicle so

what is it doing it's causing if you

notice this is a single layer this is

multiple layers that's more layers has

some follicular fluid and then a lake so

what is it doing it's causing mitosis or

proliferation of the granulosa cells

it's causing this pink membrane right

there when it goes from a primary to

early secondary at leads to the

formation of a zona pellucida which is

also in late secondary in graafian it

also is going to cause the formation of

these pockets of follicular fluid and

lekha follicular fluid which is rich in

hyaluronic acid and if you remember is

responsible for converting

not only when it goes from primary to

early secondary late secondary and

graafian it forms a sturgeon right at

least to the production of estrogen and

that was all occurring during what face

the follicular phase which was days 1 to

14 right and who was the primary

stimulus FSH and who else was released

during this time period

LH right so luteinizing hormone it's

actually acting on these cycle cells

these maroon or violet like cells and

what is it doing if you remember we had

that diagram with the thecal cells where

the thecal cells doing whenever they

receive the stimulation from LH they

were converting cholesterol into

androgens like androstenedione then the

antigens went into the nearby granulosa

cells and FSH was acting on those

granulosa cells doing what converting

those androgens into estrogens via the

aroma taste enzyme right and it was

working all of these steps ok and that

is again occurring during days 1 through

14 now what were some of the byproducts

of these reactions I told you during

their follicular phase it was estrogen

right well estrogen gets put into the

blood and around mid follicular phase so

day 7 day day 9 around that time period

estrogen levels in the blood rise and

look what happens when it gets to mid

follicular phase it comes up to the

hypothalamus and inhibits the pre optic

nucleus in the arcuate nucleus from

releasing GnRH it also inhibits the

anterior pituitary from releasing FSH

and LH if you release less FSH and loss

LH are you going to produce as much

estrogen no so as your lobes begin to

come down but guess what these cells

specifically the graphene is still

producing large amounts of estrogen and

this estrogen levels rise again but it

arises again towards the late part of

the follicular phase so like de 13 de 40

maybe even day 15 as those estrogen

levels rise again look what happens they

do something really funky they stimulate

the actual preoptic nucleus in the

arcuate nucleus to release massive

amounts of GnRH and they actually

stimulate the what the anterior

pituitary to release massive amounts of

FSH and LH

but if you noticed

FSH is actually going to be inhibited so

we're not even going to really release

FSH who's inhibiting this FSH remember

the graafian follicle as the graafian

follicle is actually nearing day 14 it

releases in heaven B and inhibin b comes

to the anterior pituitary and actually

shuts off the production of FSH that way

the only hormone is being produced

around the actual mid follicular phase

going into ovulate or e phases

luteinizing hormone and you make so much

luteinizing hormone that they call it

the LH surge and what does luteinizing

hormone do if you remember remember I

had you have blood vessels underneath

the ovary here and it was increasing the

permeability as though the blood vessels

on this side to pressurize the follicle

and make more follicular fluid and then

over in this area it was activating

proteolytic enzymes to cut around the

tissues so that we could pop that

secondary oocyte which was frozen in

metaphase to out and then eventually

into the fallopian tubes right what else

was Ellie doing not only did it trigger

ovulation which is normally at around

days 14 or 15 but it was also converting

this ruptured graafian follicle the

corporate summer had to come into the

corpus luteum which is now we're getting

ready to go into the luteal phase days

15 to 28 right and what is luteinizing

hormone doing it's stimulating the

corpus luteum to produce progesterone

okay so now let's follow this estrogen

and let's follow this progesterone and

see its effects on the actual menstrual

cycle now if you remember the menstrual

cycle it was consisting of three phases

the menstruation phase which is days 1

to 5 the proliferative phase which is

days 6 through 14 and the secretory

phase which is days 15 through 28 okay

menstruation phase you remember it was

defined as the shedding or the sloughing

off of the endometrial lining but

specifically what part of the

endometrium do you remember the

endometrium is consisting of two

different types of like sub layers or

strata one was the stratum function

Alice it was the inner layer this was

the layer that was getting shed and what

else was getting shed with it

the spiraling corley arteries that

ruptured right then underneath that one

you have the stratum ViSalus it's the

basal layer this is the one that does

not get shed and it primarily is

consisting of

nice straight arteries and one of these

arteries branches off the branches of

the uterine arteries which are branches

of the internal iliac arteries right now

around menstruation you shed the stratum

function Alice with the spiraling core

the arteries then what happens what what

days are we on now after that day six

through fourteen what was the primary

hormone made in significant amounts

during that follicular phase again

estrogen what is estrogen gonna do you

remember he's actually going to

proliferate and regenerate that stratum

function Alice layer regenerate those

spiraling coily arteries that are

supplying it make a lot of actual

uterine glands not secreted from the

uterine glands but just make a lot of

uterine glands and what else was it

doing it was causing a thin cervical

mucus production within the cervix of

the uterus why so that it was easier for

the sperm cells to move up through there

right also allows for them to get

capacitated which we talked about in

fertilization so the cervical mucus

production is very very thin okay then

what happens as we get to that point of

day 14 we reach ovulation right so now

all Asian occurs and then again what

happens luteinizing hormone converts the

rupture gravity and follicle into the

corpus luteum and then tells the corpus

luteum to start producing what hormone

primarily progesterone now I didn't

mention this before but there is tiny

amounts of FSH that's also released and

that can stimulate the corpus luteum to

make a little bit of estrogen but very

very small amounts primarily

progesterone now progesterone what is he

doing - the actual uterus he's even

making in the stratum function Alice

even thicker so he's actually causing it

to proliferate even more it's making

more of those spirally and coyly

arteries it's also causing the cervical

mucus production to switch into more of

a thick cervical plug to prevent

anything from being able to get up into

the uterus where the developing embryo

might possibly be on top of that what

else was there doing it was stimulating

those uterine glands to start producing

a broth or fluid rich in glycogen

lipids and proteins which provide a

nutritive source for the possible

developing embryo okay and then you

remember what happens as you start

getting to the point if fertilization

does not occur so fertilization does not

occur in other words the sperm doesn't

actually fertilize the egg and

don't form an embryo that implants what

happens it doesn't release human

chorionic gonadotropin if human

chorionic gonadotropin is not produced

the corpus luteum begins to degenerate

and turns into the corpus albicans

and it stops producing progesterone

progesterone levels are very very

significant important for the actual

spiraling core the arteries do you guys

remember why it causes the normal

vasoconstriction and relaxation of the

actuals the actual blood vessels the

spiraling core the arteries

so whenever progesterone level actually

decreases it causes those those vessels

to spasm and eventually the contract

relaxed contract relaxed and eventually

they rupture and you ever what happens

whenever they rupture the blood starts

accumulating within the stratum function

Alice okay whenever two key minutes

within the stratum function Alice they

don't get enough oxygen or nutrients

what happens those stratum function au

cells become ischemic and then the

chronic and then eventually what happens

it gets shed out and then what happens

you start the phase back over at

menstruation and we also said one last

thing obviously a normal female

reproductive cycle is at least 28 days

but again not every one cycle is

completely perfect

we say if it's at at least 21 days you

get little buffers to bind to about 21

days anything less than 21 days is now

pathological again you get a little bit

of buffer greater than 28 days to about

40 days if it's greater than 4 days is

now pathological okay alright guys so we

covered a lot about the female

reproductive cycle this was a nice

overview I really hope that it made

sense I hope would tide a lot of the

concepts together I hope he has really

enjoyed it um an engineer's I just

wanted to make a little announcement I

hope that you guys would just you know

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engineer its until next time

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you

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