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Reproductive System

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

The reproductive system is a group of organs responsible for reproduction. The organs and gametes of the reproductive system differs between genders- female gametes are called eggs and male gametes are called sperm. The reproductive system is also where offspring are fertilized.

The reproductive system for some unusual reasons is one of the favorite systems for a student to get interested in don't know why. Well the human reproduction system, there's a specialization in that males we make many sperm while females they make very few. Why is that? Well males do kind of are specialized while having lots and lots of gametes because the chances of any one sperm making are pretty slim so we use a whole bunch of them whereas females they focus in on quality. The way that they pull this off is that in males when we undergo meiosis or meiosis we undergo the normal way of doing it and we wind up with 4 cells and if you notice every time you divide the cell you're getting smaller but remember females when they make an egg they're trying to provide lots of resources and with humans we really do a good job of making our offspring have as much resources as possible in fact women don't release their eggs into the ocean they keep them inside their body to feed them even more resources and one of the things that they will do is that when they undergo the first division of meiosis you'll see instead of having equals set of chromosomes one of the cells gets jerk and it winds up with very little cytoplasm basically already is replaced by the chromosomes you don't need and when this cell undergoes meiosis again you wind up with a wee little nubbin over here I believe they're called bar bodies it's just this little dumping ground these polar sorry polar bodies where they just put the chromosomes that they don't need and that leaves you an egg that's roughly the size of the starting cell.

Now let's take a closer look at human female anatomy and we'll go over some of the basic parts so the ovaries sit here and there and what they do is inside of them they have thousands upon thousands of cells awaiting to become eggs and once a month one of them is given the go signal and that follicle starts to develop until finally it produces an egg through a process known as ovulation when the egg bursts out. The fallopian tubes are sitting here and they got little ends that kind of collect the eggs so one month this fallopian tube will collect an egg this month the next month that one will and so the egg comes along the fallopian tubes. Now if a woman is having intercourse with a man and he produces some semen eventually the sperm will typically fertilize the egg within the fallopian tubes. The fertilized egg will then make its way down to the uterus where that fertilized egg or zygote will embed in the wall of the uterus and during the course the woman's normal cycle she will have thicken the uterine wall with lots of extra blood vessels to help feed that child. Now once the child starts developing, eventually it's going to have to leave the woman's body and that's when it has to go through this narrow muscular pathway called the cervix and then automatically through the vagina really of course there was the man deposited semen in the vagina and the semen had to make their way through the cervix into the uterus and then randomly pick hopefully the right fallopian tube to enter.

Now I mentioned that menstrual cycle, now I don't want to go into all the details of all the hormones involved but basically it's the 28 days cycle of preparation for an egg, the actual release of the egg and that's an event called ovulation and here what we see is the developing follicle and it develops and then pops out the egg then it starts producing some chemicals to help make sure that the uterus stays ready for that egg and so this diagram here showing how in preparation the walls of the uterus get thicker and thicker and thicker but if theat egg never gets fertilized, then this corpus luteum that now used up follicle it starts to generate the hormones that it were was releasing start to drop down and eventually the woman's body gets rid of the additional lining that it made because she's not pregnant and that's when you have the menses, the menstrual flow when she releases that, that's commonly called the period, alright?

Let's take a look at the male anatomy, now it works in many ways similarly we have gonads women had an ovary, we have testis. In the testis we make our sperm those get stored in the epididymis where they are stored up until they mature and then they're released through the vas deferens and then they go zipping along this long tube and by the way if you've ever heard of vasectomy that's when a guy has that tube snipped and tied close and thus preventing him from having children. Now as they pass through there was a number of other glands the prostate gland, the seminal vesicle, the Cowper's gland they all add various chemicals to combine together to form the actual semen which is a combination of the sperm plus a number of different chemicals such as fructose to help give them food and some alkaline substances to help protect them against the acidity of the woman's in birth canal. Then ultimately they join together into the urethra. Now men are different from women, we have one tube that both urine passes through and that's our reproductive tract, women their urethra is separate from their vagina, we're close to each other but separate and then this is the urethral it's the tube that leads out of the penis to allow the semen to ultimately get into the vagina and finds its way to the egg and fertilize the egg.

And that's the reproductive system.