YouTube Transcript:
Costanzo Physiology (Chapter 10A) Reproductive Physiology Basics || Study This!

hello and welcome to the review of
costanzo's physiology textbook we're
going to start this three-part series on
chapter 10 which covers reproductive
physiology starting off with sexual
differentiation and puberty if you enjoy
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the description so reproductive
physiology centers around the gonads
which are endocrine glands so they
release hormones that go around the body
to have an effect somewhere else within
the body and these hormones support the
development and maturation of the male
and female germ cells so when it comes
to sexual differentiation of maleness or
femaleness we there are
there are three different ways of
defining sex according to this textbook
so we have genetic sex which is all
related to the sex chromosome so x y if
you're a male xx if you're a female and
then there's gonadal sex which just
relates to whether you have testes or
ovaries and then lastly is phenotypic or
genital sex which is whether the person
looks like a male or a female so it gets
into a little bit more details on each
portion here really genetic sex once
again x y is males what happens in week
7 of gestation in males with that y
chromosome there's this gene called the
sry gene which actually causes the
testes to begin developing and then the
absence of that gene and females means
that at week nine genetic females will
start to develop their ovaries when it
comes to gonadal sex we have the two
separate kinds of gonads so male gonads
and female gonads male gonads all the
testes they have these three types of
cells so your germ cells that produce
spermatogonia that will go on to produce
sperm if sertoli cells which synthesize
anti-malaria hormone that we'll talk
about later and then lathing cells which
produce our testosterone in our ovaries
or the female glonads the germ cells
obviously produce urgonia which are
surrounded by granulosa cells and stroma
to eventually form what's called an
oocyte that's going to become the egg of
a female then we also have thicker cells
which synthesize progesterone along with
granulosa cells which synthesize
estradiol now the key differences is
that in males you have anti-malarian
hormone and also testosterone being
produced and that results in a
difference in our phenotypic sex which
occurs when you're starting to
differentiate the actual male or female
reproductive tracts so for instance with
it in the womb the fetus will produce
testosterone if it's a male and then
that will stimulate the growth and
differentiation of the wolfian tracts
whereas the anti-malarian hormone will
then result in atrophy of the second set
of ducts called the malarian ducts and
these would actually would have gone on
to become the female genital tract so
since we have testosterone to cause
differentiation and growth of the male
reproductive gonads and then we have
anti-malarian hormone which causes
regression of the production or the
growth of the female genital tract then
we result in a male phenotype or female
phenotype if we have an absence of those
two hormones and although you need an
absence of these two hormones for the
differentiation and growth of the female
genital tract within the fetus you need
estrogen from the ovaries in the female
phenotype to actually help the further
growth and differentiation of the female
reproductive system so next we're going
to talk about puberty starting off with
going to troponin secretion over the
lifetime so you start to produce this
hormone called gnrh or gonadotropin
releasing hormone it's a releasing
hormone remember meaning that it's
coming from the hypothalamus so as a
releasing hormone is going to cause the
stimulation of further hormones from the
pituitary gland and those hormones is
follicle stimulating hormone or fsh and
lh or luteinizing hormone from the
pituitary gland so gnrh causes release
of the pituitary hormones fsh and
allergen and they will have effects on
the reproductive tract or reproductive
organs
so gnrh is actually going to remain
pretty low until puberty at which point
it's going to steadily rise and then
during the adult reproductive period
you're going to have pulsatile secretion
of gnrh which is going to cause
stimulation of the release of fsh and lh
initially during the adult reproductive
period you're going to have higher
levels of lh and lower levels of fsh
relatively but as we get into senescence
or you know when you're older and when
you're an older person and you're beyond
your reproductive years then fsh will
actually become higher than lh so this
pulsatile release of gnrh
during the reproductive period or you
know starting within puberty is going to
cause the release of fsh and lh which
was then going to act on our female
gonads or male gonads as well to release
testosterone and estradiol testosterone
and estrodial will then be responsible
for the appearance of our secondary sex
characteristics at puberty now the
reason why gnrh starts to become
pulsatile during puberty is still
unknown but there does seem to be
familial patterns in terms of the timing
so whether it's occurring when you're
older or whether you're younger that
seems like there's a familial pattern
but the exact reason why gnrh starts to
become pulsatile in the first place is
very much unknown at this point now it
is also unsure whether melatonin plays a
role in this onset of puberty and that's
because it can be a natural inhibitor of
dnrh release and melatonin is extremely
high during childhood and starts to
decline during adulthood so maybe that
plays a role but that's really uncertain
at this point so what happens during
puberty is that we get this volatile
flow or secretion of g and rh
in studies they have found that if you
just give a long-acting gnrh analog then
you still do not stimulate puberty so
you really need the pulsatile secretion
of gnrh to initiate puberty and what
happens is obviously you get the growth
of pubic hair the growth of the
reproductive organs and then you end up
getting a growth spurt and then you
start to produce sperm or differentiate
sperm and then also start to create the
menstruation cycle the first of which is
called the menarch and that's all
because of that pulsatile geometry
releasing fsh and lh which is going to
tell testosterone and estrogen to then
be released so that is going to be the
conclusion of this chapter a nice and
short one to get started in reproductive
physiology we're going to cover male
reproductive physiology in the next one
followed by female reproductive system
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