Female Reproductive Cycles Made Easy!
Summary
TLDRDr. Mike's video offers an in-depth look at the female reproductive cycle, detailing the ovarian and endometrial cycles. It explains the development from primordial to mature follicles and the crucial role of hormones like estrogen and progesterone. The video also covers the phases of the uterine lining, from menses through the proliferative and secretory phases, and the significance of ovulation around day 14. It concludes with the importance of implantation and the impact on the menstrual cycle.
Takeaways
- 🔬 The female reproductive cycle is approximately 28 days long, encompassing both the ovarian and endometrial cycles.
- 🌱 The ovarian cycle involves the development and maturation of the egg, starting from a primordial follicle to a mature follicle that ovulates.
- 🌡️ Hormones play a crucial role, with follicle-stimulating hormone (FSH) and luteinizing hormone (LH) being key in regulating the cycle.
- 📈 Estrogen levels rise as the follicle matures, providing negative feedback to the hypothalamus to regulate FSH and LH release.
- 📉 A surge in LH, often 24 hours before day 14, triggers ovulation, where the mature egg is released from the follicle.
- 🌕 The luteal phase follows ovulation, characterized by the formation of the corpus luteum, which produces progesterone to prepare the uterus for implantation.
- 🩸 The endometrial cycle includes the menstrual phase (bleeding), the proliferative phase (thickening of the endometrium due to estrogen), and the secretory phase (further development due to progesterone).
- 💧 The endometrium's thickness and vascularization increase during the proliferative and secretory phases to facilitate potential implantation of a fertilized egg.
- 🔄 If fertilization and implantation do not occur, the cycle resets as progesterone levels drop, leading to the sloughing of the endometrium and the start of a new menstrual cycle.
- ⏰ The timing of ovulation and the window of implantation are critical for conception, with the endometrium remaining thickened and receptive for approximately 10 days post-ovulation.
Q & A
What are the two major cycles that make up the female reproductive cycle?
-The two major cycles that make up the female reproductive cycle are the ovarian cycle and the endometrial cycle.
How long does the average female reproductive cycle last?
-The average female reproductive cycle lasts from 0 to 28 days, although it can vary between 25 to 34 days.
What happens during the follicular phase of the ovarian cycle?
-During the follicular phase, the primordial follicle matures into a primary, secondary, and then a mature follicle, which eventually ovulates.
What is the role of the zona pellucida in the process of fertilization?
-The zona pellucida is a protective layer surrounding the egg that plays a crucial role in fertilization by allowing sperm to penetrate but preventing further sperm entry once fertilization occurs.
Which hormones are primarily responsible for the follicular phase of the ovarian cycle?
-The hormones primarily responsible for the follicular phase are Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH).
Why do estrogen levels initially inhibit FSH and LH, and then later stimulate them?
-Initially, estrogen levels inhibit FSH and LH to prevent the over-stimulation of follicles. Later, as estrogen levels rise significantly, they stimulate FSH and LH, leading to a surge in LH that triggers ovulation.
What is the significance of the LH surge that occurs just before ovulation?
-The LH surge is significant because it triggers the final maturation of the follicle and the release of the egg during ovulation.
How does the endometrial cycle prepare the uterus for implantation?
-The endometrial cycle prepares the uterus for implantation by going through the proliferative phase, where the endometrium thickens due to estrogen, and the secretory phase, where it becomes more vascularized and glandular due to progesterone.
What happens if fertilization and implantation occur during the female reproductive cycle?
-If fertilization and implantation occur, the developing embryo releases human chorionic gonadotropin (hCG), which signals the corpus luteum to continue producing progesterone, maintaining the thickened endometrium and preventing menstruation.
What is the role of progesterone during the luteal phase?
-During the luteal phase, progesterone is produced by the corpus luteum to maintain the thickened endometrium, creating a suitable environment for potential implantation of a fertilized egg.
Outlines
🌱 Overview of the Female Reproductive Cycle
Dr. Mike introduces the female reproductive cycle, emphasizing the interplay between the ovarian and endometrial cycles. He outlines the cycle's duration, typically 28 days but variable, and highlights the key events within the ovary and uterus. The discussion includes the development of egg cells, the role of hormones, and the preparation of the uterus for implantation.
🔬 Ovarian and Endometrial Cycles in Detail
This section delves into the two phases of the ovarian cycle: the follicular phase, where egg cells develop and are protected by follicles, and the luteal phase, post-ovulation. The video explains the transformation from primordial to mature follicles and the critical role of hormones like estrogen. It also touches on the hormonal regulation by the hypothalamus and anterior pituitary gland, focusing on follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
📈 Hormonal Dynamics and Ovulation
The paragraph discusses the hormonal fluctuations during the female reproductive cycle, particularly the feedback mechanisms involving estrogen, FSH, and LH. It explains how estrogen levels initially inhibit and later stimulate these hormones, leading to the LH surge that triggers ovulation. The paragraph also covers the formation of the corpus luteum and its function in producing progesterone, which is crucial for the luteal phase.
🩸 Menstrual Cycle Phases and Endometrial Changes
Dr. Mike describes the three phases of the endometrial cycle: menses (bleeding), proliferative (thickening of the endometrium due to estrogen), and secretory (preparation for implantation due to progesterone). The paragraph explains how hormone levels affect the endometrial lining's thickness and function, and the importance of the implantation window for a fertilized egg.
🌟 Implantation and the Beginning of a New Cycle
The final paragraph addresses the outcome of ovulation and the potential for fertilization and implantation. It explains how the presence or absence of a fertilized egg influences the continuation or termination of the menstrual cycle. The discussion includes the role of human chorionic gonadotropin (hCG) in maintaining the corpus luteum and the subsequent production of progesterone, which supports the early stages of pregnancy or leads to the start of a new cycle if implantation does not occur.
Mindmap
Keywords
💡Female Reproductive Cycle
💡Ovarian Cycle
💡Endometrial Cycle
💡Hormones
💡Follicular Phase
💡Luteal Phase
💡Ovulation
💡Menstrual Phase
💡Estrogen
💡Progesterone
Highlights
The female reproductive cycle is composed of two major cycles: the ovarian cycle and the endometrial cycle.
The cycle typically spans from 0 to 28 days, with variations possible between 25 to 34 days.
The ovarian cycle involves the development and maturation of the egg, including follicular genesis and ovulation.
The endometrial cycle prepares the uterus for implantation through various hormonal changes.
The follicular phase of the ovarian cycle occurs from day 0 to day 14, marked by the development of the egg.
The luteal phase follows ovulation, from day 14 to day 28, where the corpus luteum produces progesterone.
Follicle-stimulating hormone (FSH) is crucial for the development of follicles into mature eggs.
Luteinizing hormone (LH) surges just before ovulation, triggered by high estrogen levels.
Estrogen levels rise during the follicular phase, providing negative feedback to regulate FSH and LH.
The endometrial lining undergoes three phases: menstruation, proliferation, and secretion.
Menstruation involves the shedding of the uterine lining, typically lasting about 5 days.
The proliferative phase is driven by estrogen, thickening and vascularizing the endometrium.
The secretory phase is influenced by progesterone, preparing the endometrium for potential embryo implantation.
If fertilization and implantation occur, the corpus luteum continues to produce progesterone, preventing menstruation.
The absence of implantation leads to a drop in progesterone levels, resulting in menstruation and the cycle restarting.
Human chorionic gonadotropin (hCG) is produced if implantation occurs, signaling the corpus luteum to maintain progesterone production.
Transcripts
hi everyone Dr Mike here in this video
we're taking a look at an overview of
the female reproductive cycle we're
going to take a look at what's happening
at the ovary what's happening at the
uterus what's happening in regards to
all the various hormones that are being
released and a lot more let's take a
look now to begin we need to understand
that the female reproductive cycle is
actually two major Cycles it's what's
happening inside the OV so the ovarian
cycle but also what's happening at the
uterus so the endometrial cycle both of
these two things are super important so
we're going to take a look at the
ovarian and uterine cycle and the
various changes that occur associated
with each and we're going to have a look
at the various hormones associated with
these changes as well now to begin we
need to understand that the ovarian and
uterine Cycles or the femal reproductive
cycle goes from 0 days to 28 days now
this is an approximate it can be lower
it can be higher but only by a little
bit it could probably be as low as 25
days and as high as 34 is days but it's
variable the average is 0 to 28 so we're
taking a look at the 0 to 28 female
reproductive cycle first of which is the
ovarian cycle so remember that there are
many things happening in the ovaries
what's happening is that this is where
our uyes are our egg cells now this is
where the genetic material resides and
this genetic material needs to replicate
it needs to undergo two phases of
meiosis but it also needs to be
nourished and protected and so this is
what's happening in the ovarian cycle is
follicular Genesis which is the
development of the follicles that
protect the egg but then also what
happens after the egg is ovulated we're
going to have a look at the endometrial
cycle as well so this is what's
happening at the uterus to prepare it
for implantation and the hormones
ovarian cycle to begin with there are
two major phases associated with the
ovarian cycle the first phase is that of
what we call the folicular
phase the follicular
phase the second phase is what we call
the luteal
phase the
luteal
phase now as you can see because we've
broken it up in accordance with days
here that from 0 to 14
we have the folicular phase and then
from day 14 to 28 we have the luteal
phase let's take a look at this to begin
with because the follicular phase is
associated with taking the uite or the
egg for example so here's the uite or
egg in a primordial form now that
primordial uite will turn into a primary
uite and this primary uite and I'm not
going to write that up yet this primary
oite is surrounded by a thin layer of
cells and this thin layer of cells we
call pregranulosa
cells pregranulosa
cells and the whole thing with the
pregranulosa cells and
the uite and this is called a
primary
uite this is called a
primordial follicle
primordial follicle now this primordial
follicle will start to mature and
develop and over time what's going to
happen throughout this follicular phase
so going from day Zer to day 14 is this
primordial follicle will get that
oite and those pregranulosa cells will
turn into granulosa cells more
cuboidal shaped cells and the uite will
be surrounded by this thing called a
Zona
paluca which helps prot protect it and
is very important when it comes to
fertilization once the sperm gets into
that zone of paluca it's like the screen
doors of the house all shut and don't
let any more sperm in so now we've got
these
granulosa granulosa cells and we've got
the zon of
paluca as well zon of
paluca and this is what we call a
primary follicle so it goes from a
primordial follicle to a primary
follicle now this whole time it's still
a primary uite so don't get that
confused even though the follicle name
changes it goes from a primary follicle
into a secondary
follicle and the secondary follicle is
very similar still has the zone of
paluca except there's one major change
well a couple first of which is you can
have a couple of layers of granulosa
cells so I'm just going to draw it up
like this and you're going to have some
additional cells called ther cells so
you have these ther cells now on the
outside here so these are
ther
cells and you still have your granulosa
cells and you still have your zone of
paluca
granua
cells this now is called a secondary
follicle
secondary
follicle and this secondary follicle
will turn into now I haven't told you
about what they do I will I promise I'm
just going through the phases the
secondary follicle will turn into a
mature ultimately a mature follicle now
what this mature follicle does by day 14
is it ovulates now what that means is
that you have these granular cells like
this you have these F cells that have
now developed even further right on the
outside and the uite
has ovulated and it takes some cells
with it because it still needs to be
nourished right now that's an important
point because I haven't told you what
any of these cells do as it goes from
Day Z to day 14 the development of this
follicle these follicles which we call
the follicular phase from a primordial
follicle to a primary follicle to a
secondary follicle to what we call a
mature or graffian so let's call this an
anol or let's call it a
graphion or you could even call it a
mature follicle
right this is the one that ovulates now
the granulosa cells and the Thea cells
are super important what the granulosa
and ther cells do is they ultimately
produce estrogen now specifically one
type of estrogen that's most important
here is called estral now here's the
thing this whole process
going from here to around about here is
independent of any hormones it really
doesn't need hormones to do this right
now if we have a look down and look at
the hormones what's happening during
this process let's first focus on
luteinizing hormone and follicle
stimulating hormone now remember these
hormones these two here they're
ultimately
released from the
hypothalmus right specifically they're
released from the anterior pituitary
gland so what happens is the
hypothalmus the
hypo thelus will release a hormone
called gonadotropin releasing hormone
and this goes down to the anterior
aspect of the pituitary
gland which then
releases these hormones this happens at
puberty right now let's have a look at
what's happening at these hormones
lutenizing hormone and follicle
stimulating hormone they're not super
high right let's start with ltin let's
start with uh follicle stimulating
hormone so what you'll find here is that
follicle stimulating hormone at Day Zero
is up
here and it starts to drop down right
let's do the same with lutenizing
hormone right lutenizing hormone it's
here and it starts
to drop down slowly interesting now
importantly what these two hormones do
most specifically follicle stimulating
hormone is by the time we hit this phase
here we need follicle stimulating
hormone to
stimulate these secondary follicles to
turn into more mature follicles to these
anal follicles graphium follicles more
mature follicles we need FSH for this if
FSH isn't here at this step what ends up
happening is these cells just all die
off now every month right at Day Zero
you have around about 10 to 30 of these
these follicles undergoing this process
and again without FSH they'll all just
undergo a treesia and die so what you'll
find is that because FSH is released it
allows for that selection process now
here's the other thing that's important
as it selects and it's going to take
from 10 to 30 it's only going to select
one right one mature one to ovulate one
single ovam as it does this and these
granulosa and ther cells get bigger and
bigger and bigger these granulosa and
Thea cells produce estrogen so as the as
the follicle develops the estrogen right
estral specifically it starts low but it
starts to
go
higher now can you see a pattern here
right as the estrogen gets higher the
FSH and LH gets lower this is important
because the estrogen that's released
from these Thea and granulosa cells goes
back to the
hypothalmus and says and provides
negative feedback says stop releasing G
outat trop and releasing hormone stop
releasing luteinizing hormone and
follicle stimulating hormone why would
it want to do that it does that because
it's now already selected its one mature
follicle that it wants so there's no
point continually releasing these
hormones to keep this process happening
we want it these to stop and just have
that one selected one now the estrogen
will continue to go up and inhibit the
FSH and LH until something important
happens right so again we're not at day
14 yet we're not at this point what
we're going to find is as we get just
maybe like 24 hours before day 14 the
estrogen levels that are released by
these ther and granulosis cells it's
starts to just Spike right up now here's
the interesting thing while relatively
low levels of estrogen inhibit FSH and
LH high levels of estrogen stimulate
them we don't know why but it does and
so when we have this higher level of
estrogen and it stimulates FSH and LH
what we end up
getting is the FSH down here and the LH
down here but once it starts to get
right once these levels start to get
high enough we get a surge now the surge
in this case predominately is going to
be that
of lutenizing hormone we also get a
surge of
FSH but importantly we've got this big
surge of LH and again this big surge of
LH is happening just before day4 and
what this big surge of LH does is FSH
follicle stimulating hormone is really
important in the follicular phase that
makes sense right so FSH is really
important in this phase
here at day 14 where we have ovulation
let's write that down I think that's
important day 14 where we have ovulation
occurring this is
important because of
LH LH is responsible for that ovulation
beautiful so that's because of that
Spike there now the thing is that once
this
happens we've got the ovulation
occurring the egg has been taken up by
the fim and is now in the uterine tube
right the fallopian tube let's just have
a look here right this remaining thing
here if I were to draw it
across we're now in the luteal phase
right so we've now got this
big empty looking body
and this big empty looking body starts
to produce a whole bunch of
progesterone this is called the corpus
luteum hence why it's called the luteal
phase so this is called the Corpus
Corpus means body right
luteum luteal means yellow it looks
yellow right because
cholesterol we turn
cholesterol
into
progesterone and we turn
progesterone into androgens right like
testosterone and we turn
androgens into
estrogen like
estradiol all comes from cholesterol so
what's happening in this corpus luteum
phase that goes throughout this process
here is it starts to produce huge
amounts of progesterone so what we end
up getting is low levels of progesterone
through most of this process we have a
little bit of a spike here but once we
hit day 14 and this corpus luteum
happens we get this big
spike of progesterone right we get this
big spike of progesterone what happens
with all these other ones they start to
drop off again so we got estrogen
dropping off we've got follicle
stimulating hormone dropping
off and we've got oh sorry luteinizing
hormone dropping off and we've got
follicle stimulating hormone dropping
off but here for this luteal phase we've
got heaps of progesterone all right we
haven't spoken at all about what's
happening in the endometrium so
far the endometrial lining or the
endometrium or the uterus has three
major phases the first phase is called
menes and this is
bleeding now as you can see menes goes
to round about day
five day five and then after bleeding
after menes we've got the proliferative
phase we've got the proliferative
phase
proliferative and then we've got the
secretory
phase now remember this this is what's
happening at the endometrium the
secretory phase so if we look at
endometrial changes that occur so just
so we've got enough room I'm going to
drop these because I didn't do units
it's okay I'm just looking at gross
changes that happen so that's not a
problem I didn't do any units on purpose
and it's important to understand the
unit changes here because some are
measured in
microliters uh micrograms per microl or
mil some are measured in pics nanog so
they're all you can't compare them in
regards to their concentrations this is
just general uh spikes for example and
Peaks and troughs now the endometrium
what happens menes menes is bleeding
goes for about 5 days if we have a look
at the thickness of the uterus it like
this it's going to be thick and then it
starts to bleed away and Slough off so
if this whole thing was the what we call
the functional layer of the uter of the
endometrial lining we're focusing on the
functional layer the functional layer is
the layer that can implant the
fertilized embryo but also can thicken
become more vascularized and produce
enzymes and uh various secretions like
mucus during menes the uterine lining
gets thinner and that's because bleeding
is occurring it's sloughing off this
sloughing off is happening because the
hormone levels are really low that's
important but as you can see in the
proliferative phase it starts to get
thicker again now it's getting thicker
again because we're starting to get an
increase in estrogen levels what
estrogen does is it increases the
thickness of the endometrium right so it
starts to get thicker that's great as
you can see as we move through and not
just uh estrogen is being produced we
now start getting progesterone
progesterone reinforces this and says
hey endometrium get thicker get more
vascularized and by the so here we got
the proliferative phase this is simply
just saying get thicker get thicker get
thicker get thicker right then the
secretory phase is saying now start to
develop glands start to develop glands
and this is in big part due to
Progesterone that we can now produce
enzymes that we can now produce mucus
and so forth and then what we end up
getting is once these hormones like
progesterone start to drop back down
again towards 28 days and once estrogens
drop back down again and then once
follicle stimulating hormone lutenizing
hormone have dropped back down
again the hormones are low again at the
end of day 28 and like I said the low
hormones is what causes the sloughing so
towards the end of day 28 we start to
get that drop down again so we've got
Menses which is bleeding that's
happening at this stage proliferation
this is all right so let's think about
it like this right follicular phase is
very much so due to FSH luteal phase is
very much due to
LH like I said FSH helps to produce
estrogen right so the proliferative
phase is really important uh when it
comes uh estrogen is really important
when it comes to the proliferative phase
the secretory phase luteinizing hormone
which produces ovul ovulation of Corpus
Lum and ultimately produces heaps of
progesterone is very much so due to
Progesterone
now this there's a huge amount of
overlap obviously because LH is
important here and FSH is important here
progesterone is important here and
estrogen's important here but broadly
generally speaking these are the
important hormones involved mostly in
these Cycles or this uh these phases of
the Cycles so importantly day 14
ovulation right day 28 hormone levels go
low again from Day Zero they start to go
back up estrogen is inversely
proportional to the FSH and LH so
they're going outat tropin until the
estrogen levels get quite High then they
both Spike that spiking of the LH maybe
24 hours before day 14 is what
stimulates ultimately ovulation to occur
the LH helps stimulate the Corpus Lam to
produce progesterone and this
progesterone as you can see will last
around about 10 days right so the this
progesterone is really important lasts
around about 10 days
is and then drops back down down why
well this Corpus Lum will release the
progesterone for round about the 10 days
and what it's doing is it's basically
said it's basically said to the egg that
it's ovulated remember where's this egg
now this egg has gone into the fim and
has been taken in and is in the uterine
tube and it's in the ampul and hopefully
fertilization occurs if fertilization by
sperm occurs that egg which then starts
to grow and divide as it moves through
the uterine tube can hopefully implant
in this nice thick endometrium that's
developed right in this window is here
so this is we've got this important
window here where it needs to implant if
it and so we've got this progesterone
being released to keep the endometrium
nice and thick for that implantation
window but if there's no sperm and
there's no fertilization there's no
implantation what ends up happening is
that once it does if it does get
fertiliz and implanted it starts to
produce a hormone called human chonic
gonadotropin so if it does implant right
if it does implant and start to divide
and so forth it will release
human
chonic gadat
tropen basically it pretends to be gadat
tropen and it is like a phone call back
to the Corpus lium saying hey
everything's good I'm here keep
producing progesterone so if that does
get implanted that doesn't stop at 28
days it keeps going that means if it
keeps going it stays thick so that the
embryo can develop and you don't get
Menses you don't get bleeding but if
there's no implantation there's no human
caronic Gat tropin there's no phone call
back after 10 days it stops producing
progesterone and the tissue starts to
diminish and sloughs Away you get
bleeding that's mens's the whole cycle
starts again so I hope that this helps
and this makes
sense hi everyone Dr Mike here if you
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