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  • - Welcome to the reproductive system.

  • So, let's start by asking,

  • "What is the reproductive system?"

  • It's basically a system in our bodies that includes

  • our sex organs and certain parts of our brain.

  • You can see the sex organs here on the male,

  • and here in two places on the female.

  • So, this system within our bodies allows us to reproduce,

  • it allows us to make babies.

  • And to make babies what we're doing is combining

  • genetic material from a biological mother's egg

  • and a biological father's sperm to make our offspring.

  • And we typically do this by sexual intercourse.

  • So, let's first take a brief look at a couple of

  • the most important sex organs that make males

  • and females have in their reproductive systems.

  • So, the males have the testes.

  • And these are the most important structures.

  • Sort of the structures that everything else

  • is built around in a male.

  • And that's because the testes produce

  • his contribution to a baby.

  • They make these small mobile cells

  • that carry his genetic material into a female

  • to fuse with her genetic material to cause a pregnancy.

  • And these small mobile cells are his sperm.

  • Another important male organ is the penis.

  • And the penis is used to deliver

  • his sperm inside the female mate

  • to increase the chance that it meets her egg.

  • So, those are really the major male organs.

  • Now on the female side,

  • one of her major organs is the ovary

  • and she has two just like how males have two testes.

  • And in fact the ovaries and testes are homologous,

  • they came from the same precursor in development.

  • Now the ovaries are responsible for producing the female's

  • genetic contribution to a baby, that is the egg.

  • The ovaries, though, are a lot different to the testes,

  • in that the testes are constantly producing

  • lots and lots of sperm.

  • To the tune of of millions per day.

  • Where as the ovaries only release one egg per month.

  • So, the next really important female organ

  • is called the uterus.

  • And the uterus is basically a really thick muscular organ

  • that's capable of stretching out

  • and it's actually where the baby's actually developing

  • during pregnancy until birth.

  • The next really important female structures are the breasts.

  • And the breasts are important because they produce milk

  • during the pregnancy and afterwords

  • via a process called lactation.

  • And lactation happens due to a series of hormones

  • that generally get released around pregnancy.

  • So, this breast milk that gets produced can feed

  • and nourish the growing baby

  • and it actually plays a roll in creating

  • a stronger immune system for the baby.

  • So, we've seen some of the major structures

  • of both male and female reproductive systems.

  • But is that all the reproductive systems are?

  • Actually, no.

  • Besides producing the sperm and egg,

  • the reproductive systems produce chemicals

  • whose signals have a really strong influence

  • over activities in our bodies.

  • We call these chemicals, hormones

  • and because they come from our reproductive systems

  • we refer to them as our sex hormones.

  • For example, the male's major sex hormone, testosterone,

  • which is actually produced in the testes,

  • is responsible for many masculine traits.

  • Such as body hair, the deepening of your voice,

  • muscle growth, and there's possibly even a link

  • to levels of aggression in males.

  • On the female side of things, the ovary is the primary

  • producer of some major female hormones,

  • like estrogen and progesterone.

  • Estrogen and progesterone play a major roll in the timing

  • of egg release from the ovaries.

  • Estrogen is also responsible for the development

  • of a lot of feminine traits.

  • For example, breast development.

  • So, there's the making of the sperm and the egg,

  • there's the production of the major sex hormones.

  • What else does the reproductive system do?

  • Well it does one more really important thing.

  • And that's coordinate the meeting of the sperm and the egg.

  • And it does that by the males penis and the females vagina.

  • These two organs are used to ensure

  • that the sperm and the egg meet each other.

  • So, the penis actually deposits sperm within the vagina,

  • so that sperm has a better chance of reaching

  • and fertilizing the egg released

  • inside her reproductive tract.

  • So, you might be thinking, "Does the reproductive system

  • "do all this stuff on it's own?"

  • I mean what tells it what to do?

  • And that's a good question.

  • The reproductive system is actually controlled by the brain.

  • There's an area in the brain called the hypothalamus

  • that sits just about there on the inside of the brain,

  • just about in the middle.

  • And the hypothalamus actually releases a hormone

  • called gonadotropin releasing hormone or GNRH.

  • GNRH effects another part of the brain called,

  • anteriorpituitary which sits right about there

  • just under the hypothalamus.

  • And anteriorpituitary in response to GNRH releases

  • two hormones lutenizing hormone or LH

  • and follicle stimulating hormone or FSH.

  • And its the lutenizing hormone

  • and the follicle stimulating hormone

  • that primarily effect the male and female sex organs.

  • So, the male's testes and the female's ovaries

  • to control their functions.

  • Finally, a word on pregnancy,

  • as pregnancy is a huge part of reproduction

  • and certainly the most long lasting part.

  • So, pregnancy results when a sperm successfully

  • fertilizes an egg to create a zygote.

  • A zygote is a first cell in a new organism

  • that has genetic material from both mom and dad.

  • And that genetic material has come from the sperm

  • and the egg that have fused.

  • The zygote goes through a series of developments

  • and eventually implants itself within the inner wall

  • of a woman's uterus to grow.

  • So, that's in here,

  • remember that thick muscular organ we talked about?

  • The third step is what we'll really broadly call gestation.

  • Gestation is basically the development

  • of the fetus into a baby.

  • So, the development of all the fetus's organ systems

  • including their brains, spinal cord, lungs,

  • cardiovascular system, their reproductive system,

  • all the systems in their body.

  • Gestation readies the developing infant to be born.

  • And it takes about nine months.

  • When the babies ready to come out of the uterus

  • and into the world a number of hormonal

  • changes take place in the mother's body.

  • This signals her to start getting ready to push

  • the baby out of her body, in other words,

  • give birth to the baby.

  • She then goes through a process called labor,

  • also known as parturition, to give birth to the baby.

  • After the baby's born,

  • the last step is to give him or her a name.

- Welcome to the reproductive system.

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生殖システムへようこそ (Welcome to the reproductive system )

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    Amy.Lin に公開 2021 年 01 月 14 日
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