0:00 hello and welcome to the review of
0:01 costanzo's physiology textbook we're
0:03 going to start this three-part series on
0:05 chapter 10 which covers reproductive
0:08 physiology starting off with sexual
0:10 differentiation and puberty if you enjoy
0:12 the video please don't forget to give it
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0:15 you want access to exclusive content you
0:17 can find that in the patreon link within
0:19 the description so reproductive
0:21 physiology centers around the gonads
0:24 which are endocrine glands so they
0:26 release hormones that go around the body
0:28 to have an effect somewhere else within
0:30 the body and these hormones support the
0:32 development and maturation of the male
0:34 and female germ cells so when it comes
0:37 to sexual differentiation of maleness or
0:39 femaleness we there are
0:41 there are three different ways of
0:43 defining sex according to this textbook
0:46 so we have genetic sex which is all
0:48 related to the sex chromosome so x y if
0:52 you're a male xx if you're a female and
0:54 then there's gonadal sex which just
0:56 relates to whether you have testes or
0:58 ovaries and then lastly is phenotypic or
1:01 genital sex which is whether the person
1:03 looks like a male or a female so it gets
1:05 into a little bit more details on each
1:07 portion here really genetic sex once
1:10 again x y is males what happens in week
1:13 7 of gestation in males with that y
1:15 chromosome there's this gene called the
1:17 sry gene which actually causes the
1:20 testes to begin developing and then the
1:22 absence of that gene and females means
1:24 that at week nine genetic females will
1:27 start to develop their ovaries when it
1:28 comes to gonadal sex we have the two
1:31 separate kinds of gonads so male gonads
1:33 and female gonads male gonads all the
1:35 testes they have these three types of
1:37 cells so your germ cells that produce
1:39 spermatogonia that will go on to produce
1:41 sperm if sertoli cells which synthesize
1:44 anti-malaria hormone that we'll talk
1:46 about later and then lathing cells which
1:48 produce our testosterone in our ovaries
1:50 or the female glonads the germ cells
1:52 obviously produce urgonia which are
1:54 surrounded by granulosa cells and stroma
1:57 to eventually form what's called an
1:58 oocyte that's going to become the egg of
2:01 a female then we also have thicker cells
2:03 which synthesize progesterone along with
2:06 granulosa cells which synthesize
2:08 estradiol now the key differences is
2:11 that in males you have anti-malarian
2:13 hormone and also testosterone being
2:16 produced and that results in a
2:18 difference in our phenotypic sex which
2:21 occurs when you're starting to
2:22 differentiate the actual male or female
2:26 reproductive tracts so for instance with
2:29 it in the womb the fetus will produce
2:31 testosterone if it's a male and then
2:33 that will stimulate the growth and
2:35 differentiation of the wolfian tracts
2:37 whereas the anti-malarian hormone will
2:39 then result in atrophy of the second set
2:43 of ducts called the malarian ducts and
2:45 these would actually would have gone on
2:47 to become the female genital tract so
2:50 since we have testosterone to cause
2:52 differentiation and growth of the male
2:55 reproductive gonads and then we have
2:57 anti-malarian hormone which causes
2:59 regression of the production or the
3:02 growth of the female genital tract then
3:04 we result in a male phenotype or female
3:08 phenotype if we have an absence of those
3:09 two hormones and although you need an
3:11 absence of these two hormones for the
3:14 differentiation and growth of the female
3:16 genital tract within the fetus you need
3:18 estrogen from the ovaries in the female
3:21 phenotype to actually help the further
3:24 growth and differentiation of the female
3:28 reproductive system so next we're going
3:30 to talk about puberty starting off with
3:32 going to troponin secretion over the
3:34 lifetime so you start to produce this
3:36 hormone called gnrh or gonadotropin
3:39 releasing hormone it's a releasing
3:41 hormone remember meaning that it's
3:43 coming from the hypothalamus so as a
3:46 releasing hormone is going to cause the
3:47 stimulation of further hormones from the
3:50 pituitary gland and those hormones is
3:53 follicle stimulating hormone or fsh and
3:56 lh or luteinizing hormone from the
3:57 pituitary gland so gnrh causes release
4:01 of the pituitary hormones fsh and
4:03 allergen and they will have effects on
4:05 the reproductive tract or reproductive
4:08 organs
4:09 so gnrh is actually going to remain
4:11 pretty low until puberty at which point
4:14 it's going to steadily rise and then
4:15 during the adult reproductive period
4:18 you're going to have pulsatile secretion
4:20 of gnrh which is going to cause
4:22 stimulation of the release of fsh and lh
4:25 initially during the adult reproductive
4:28 period you're going to have higher
4:30 levels of lh and lower levels of fsh
4:34 relatively but as we get into senescence
4:36 or you know when you're older and when
4:38 you're an older person and you're beyond
4:40 your reproductive years then fsh will
4:43 actually become higher than lh so this
4:46 pulsatile release of gnrh
4:48 during the reproductive period or you
4:51 know starting within puberty is going to
4:53 cause the release of fsh and lh which
4:55 was then going to act on our female
4:58 gonads or male gonads as well to release
5:00 testosterone and estradiol testosterone
5:03 and estrodial will then be responsible
5:05 for the appearance of our secondary sex
5:07 characteristics at puberty now the
5:09 reason why gnrh starts to become
5:12 pulsatile during puberty is still
5:14 unknown but there does seem to be
5:16 familial patterns in terms of the timing
5:19 so whether it's occurring when you're
5:20 older or whether you're younger that
5:22 seems like there's a familial pattern
5:24 but the exact reason why gnrh starts to
5:27 become pulsatile in the first place is
5:30 very much unknown at this point now it
5:32 is also unsure whether melatonin plays a
5:35 role in this onset of puberty and that's
5:38 because it can be a natural inhibitor of
5:40 dnrh release and melatonin is extremely
5:43 high during childhood and starts to
5:46 decline during adulthood so maybe that
5:48 plays a role but that's really uncertain
5:50 at this point so what happens during
5:52 puberty is that we get this volatile
5:55 flow or secretion of g and rh
5:58 in studies they have found that if you
5:59 just give a long-acting gnrh analog then
6:03 you still do not stimulate puberty so
6:06 you really need the pulsatile secretion
6:08 of gnrh to initiate puberty and what
6:11 happens is obviously you get the growth
6:13 of pubic hair the growth of the
6:15 reproductive organs and then you end up
6:18 getting a growth spurt and then you
6:20 start to produce sperm or differentiate
6:23 sperm and then also start to create the
6:25 menstruation cycle the first of which is
6:27 called the menarch and that's all
6:29 because of that pulsatile geometry
6:31 releasing fsh and lh which is going to
6:33 tell testosterone and estrogen to then
6:36 be released so that is going to be the
6:38 conclusion of this chapter a nice and
6:39 short one to get started in reproductive
6:41 physiology we're going to cover male
6:43 reproductive physiology in the next one
6:45 followed by female reproductive system
6:48 after that if you enjoyed the video
6:49 please don't forget to subscribe as it
6:51 helps our channel grow and other people
6:53 see it and once again if you'd like to
6:55 get access to exclusive content you can
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6:58 description feel free to drop a comment
7:01 otherwise we'll see in the next one
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