HORMON PADA SISTEM REPRODUKSI MANUSIA
a. Hormone pada sistem reproduksi pria
1. Gonadotropin hormone (GnRH), dihasilkan oleh kelenjar pituitary anterior (hipofisis anterior) yang terdiri dari:
· Luteinizing Hormone (LH), berfungsi merangsang sel-sel Leydig testis untuk menghasilkan tostesteron
· Folicle Stimulating Hormone (FSH), berfungsi merangsang perkembangan spermatosit dalam proses spermatogenesis, khususnya merangsang sel-sel sertoli pada perubahan spermatid menjadi sperma. Perhatikan animasi dibawah ini!
Untuk melihat kontrol hormon pada sistem reproduksi pria, kamu dapat melihat pada video dibawah ini.
The hypothalamus produces a releasing hormone, GnRH, that regulates the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. FSH stimulates sperm production by the testes. LH stimulates the testes to secrete androgens-- male sex hormones. Testosterone is the most important androgen secreted by the testes. Androgens shape the development of the male reproductive system. They stimulate sperm production, and trigger development of secondary sex characteristics such as beard growth
Negative feedback regulates the function of the male reproductive system. An increase in testosterone and other androgens inhibits the brain and pituitary, decreasing secretion of releasing hormone and LH. This in turn reduces androgen secretion. A drop in androgens allows the brain and pituitary to stimulate the testes, maintaining optimum androgen levels.
2. Androgen
Merupakan hormone steroid. Salah satu hormone ini adalah tostesteron. Tostesteron disekresikan oleh sel-sel Leydig testis. Tostesteron berfungsi dalam perkembangan sel germinal dalam proses spermatogenesis. Selain itu, tostesteron sangat penting dalam menentukan sifat kelamin sekunder para pria, contohnya tumbuhnya rambut pada area tertentu, perbesaran suara dan perkembangan otot yang terjadi ketika masa pubertas.
3. Estrogen
Dibentuk oleh sel sertoli ketika ada stimulus oleh FSH. Hormon ini berperan dalam proses pematangan sperma.
b. Hormone pada sistem reproduksi wanita
1. Gonadotropin Hormone (GnRH), dihasilkan oleh kelenjar pituitary anterior (hipofisis anterior) yang terdiri dari:
· Luteinizing Hormone (LH), berperan dalam merangsang pelepasan oosit skunder dari folikel tersier (de graf) sehingga terjadi ovulasi.
· Folicle Stimulating Hormone (FSH), merangsang pertumbuhan folikel telur pada ovarium.
2. Estrogen, disekresikan seiring dengan perkembangan folikel. Estrogen juga diproduksi oleh korpus luteum dan plasenta. Fungsi estrogen adalah:
· Merangsang pembentukan kembali (proliferasi) sel penyusun endometrium.
· mempengaruhi serviks menghasilkan lendir yang bersifat basa pada vagina sehingga mendukung kelangsungan hidup sperma ketika masuk ke vagina
· Sangat berperan dalam menentukan sifat kelamin sekunder wanita.
· Berperan dalam kontraksi uterus ketika proses persalinan.
3. Progesterone, dihasilkan oleh korpus luteum (folikel yang telah melepaskan ovumnya), berfungsi sebagai:
· Mendukung fungsi estrogen dalam penebalan endometrium
· Merangsang sekresi lendir pada vagina
· Merangsang pertumbuhan kelenjar susu
4. Oksitosin, disekresikan oleh hipofisis wanita, berperan merangsang kontraksi uterus pada saat persalinan
5. Prostaglandin, disekrsikan oleh membrane janin, berfungsi meningkatkan intensitas kontraksi uterus rahim ketika proses persalinan
6. Relaksin, dihasilkan oleh plasenta dan korpus luteum pada ovarium, berfungsi merelaksasi dan melunakkan serviks serta melonggarkan tulang panggul sehingga mempermudah persalinan.
7. Mammotropin, disekresikan oleh hipofisis dan plasenta, berfungsi merangsang pertumbuhan awal kelenjar susu (glandula mamae).
8. Prolaktin, disekresikan oleh hipofisis ibu pada minggu kelima kehamilan, berfungsi meningkatkan sekresi air susu oleh glandula mamae.
Untuk melihat kontrol hormon pada wanita, dapat dilihat pada video dibawah ini!
The brain controls reproduction, acting via hormones produced by the pituitary gland. While a woman is menstruating, her hypothalamus begins secreting a releasing hormone, which stimulates the anterior pituitary to secrete FSH and LH into the blood. FSH-- follicle stimulating hormone-- stimulates the growth of an ovarian follicle in the ovary. The follicle consists of a developing egg cell surrounded by cells that nourish and protect it. The developing follicle begins secreting estrogen, a female sex hormone. Estrogen shapes development of the female reproductive system and female secondary sex characteristics such as broad hips and development of the breasts. Its immediate role is to stimulate regrowth of the lining of the uterus, in preparation for possible pregnancy. Low levels of estrogen also exert negative feedback on the hypothalamus, keeping blood levels of FSH and LH relatively low.Basically what is going on here is that the brain triggers development of an egg, and the follicle containing the egg signals the uterus to prepare to support the development of an embryo. Negative feedback assures that only one follicle develops at a time.
As the follicle grows, it secretes more and more estrogen. This stimulates further development and thickening of the uterine lining. Estrogen level reaches a peak just before the mid-point of the cycle. Now response of the hypothalamus and pituitary to estrogen reverses. The higher level of estrogen actually stimulates the hypothalamus to signal the pituitary to secrete a burst of FSH and LH.It is the burst of LH that triggers ovulation on about day 14 of the cycle. The ovum develops, the follicle ruptures, and the nearly mature ovum is released from the follicle and swept into the oviduct.LH-- or luteinizing hormone-- also causes the ruptured follicle to develop into a glandular structure called the corpus luteum.
After ovulation, the corpus luteum continues to secrete estrogen and increasing amounts of a second female hormone called progesterone. Both hormones contribute to further thickening of the uterine lining, in preparation for possible pregnancy. Estrogen and progesterone also exert negative feedback on the hypothalamus and pituitary, suppressing FSH and LH secretion. This keeps additional follicles from developing after ovulation.We can summarize ovulation and the following events like this: When the follicle is nearly mature, it signals the hypothalamus to trigger ovulation. The ruptured follicle-- now called the corpus luteum-- prevents additional follicles from developing, and signals the uterus to prepare for implantation and development of an embryo. What happens next depends on whether the ovum is fertilized or not.
If the egg is not fertilized, the corpus luteum has a short life span. Suppression of LH after ovulation causes the corpus luteum to degenerate. As the corpus luteum's output of estrogen and progesterone drops, two changes occur. The lining of the uterus begins to slough off-- the beginning of the menstrual period and start of the next cycle. The drop in estrogen and progesterone also reduces feedback inhibition of the hypothalamus and pituitary. This triggers secretion of FSH and LH, which stimulates the development of a new follicle.So, if fertilization doesn't occur, the corpus luteum degenerates. Without its hormones, the lining of the uterus breaks down and a new follicle starts to grow.
If the egg is fertilized, it starts to develop and implants in the wall of the uterus. The embryo secretes a hormone called human chorionic gonadotropin-- HCG for short. HCG functions like LH to signal the corpus luteum to continue its secretion of estrogen and progesterone. (Later the placenta takes over this function.) Progesterone and estrogen maintain the lining of the uterus and suppress development of any more follicles. In effect, the embryo signals the corpus luteum to stick around, maintaining the uterus for embryonic development and stopping the monthly cycle.Human reproduction is complicated! It depends on precise coordination of the ovaries and uterus, in response to hormonal signals orchestrated by the brain.
