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coolerthanthouSpermatogenesis
Seminiferous tubules contains germ cells. Peripheral germ cells are called spermatogonia and actively divides themselves through mitosis and some of the end products are the primary spermatocytes (2N). Primary spermatocytes undergoes the 1st meiotic division to produce 2 secondary spermatocytes. The secondary spermatocytes then undergoes the 2nd meiotic division to produce 2 spermatids. The spermatids then goes through a major transformation to be a spermatozoon, which is sperm cells.
Menses
Progesterone and estrogen levels drops as corpus luteum degenerates. FSH and LH levels drops and the superficial layer of the endometrium is being sloughed off. Menses would lasts for 4 to 5 days.
Proliferative Phase
FSH and LH levels are only slightly elevated through most of the proliferative phase. Developing follicle, due to FSH, releases increasing levels of estrogen near the end of the proliferative phase and sustained high levels of estrogen have positive feedback to FSH and LH. This causes the FSH and LH levels to rise rapidly near the end of the proliferative phase. Estrogen causes the endometrium of the uterus to thicken and develop tube-like glands.
Secretive Phase
FSH and LH levels remain low throughout due to progesterone and estrogen inhibition. Corpus luteum secretes high level of progesterone. Progesterone causes the final development of endometrium and maintains it. Tube-like glands begin to secrete some fluid. If fertilization does not occur, corpus luteum will degenerate after 25 days (day 28) and progesterone levels drops significantly. Superficial layer of endometrium beings to slough off, menses begin.
Ovulation Phase
FSH and LH levels rise rapidly due to the rising levels of estrogen. LH cause final maturation of the follicle and ovulation to occur. Ruptured follicle develops into corpus leteum . Corpus leteum begins secreting large amount of progesterone and some estrogen. Progesterone and estrogen begin inhibiting FSH and LH release. FSH and LH levels drop rapidly after ovulation.
If fertilization occurs, the fusion of sperm (N) and oocyte (N) -> zygote (2N). Zygote undergoes mitosis and becomes an embryo. Implantation of the embryo occurs at the endometrium. Placenta, which is rich in blood supply and is connected to the umbilical cord, forms. Exchanges of nutrients, gases, metabolic wastes between the embryo and the mother takes place there. Lining of the endometrium must be maintained.
Pregnancy = 9 months and 10 days = 118 days.
Trimester = 3 months ; By the third trimester, the baby's head should be at the bottom.
1st Trimester
Placenta releases human chrionic gonadotropin (hCG) and hCG stimulates corpus luteum to secrete progesterone and estrogen.
2nd Trimester
Placenta begins releasing progesterone and estrogen.
3rd Trimester
Placenta completely takes over the corpus leteum in releasing progesterone and estrogen.
Hormonal Regulation
Hypothalamus secretes gonadotropin-releasing (GnRH) hormone that stimulates anterior pituitary gland to release FSH and LH. Testosterone has a negative feelback effect on GnRH, FSH and LH release. Before puberty, testosterone produced in small amounts by testes and adrenal cortex. This inhibits GnRH, FSH and LH secetion. At puberty, hypothalamus and anterior pituitary gland become less sensitive to testosterone inhibition. This results in elevated levels of GnRH, FSH and LH.
Oogenesis
Begins in the foetus. Oogonia (from which oocytes arises) undergo 1st meiotic division but are arrested at prophase I -> Primary oocytes. Primary oocytes remain dormant until puberty. Every month, one primary ooctye is activated and completes 1st meiotic division just before ovulation and the secondary ooctye (daughter cell, large) and polar body (small daughter cell). Secondary oocyte begins the 2nd meiotic division but is arrested at metaphase II. Ovulation occurs and the second oocyte is released. Fertilization occurs when a sperm penetrates the secondary oocyte. Secondary oocyte completes the 2nd meiotic division which gives rise to 2 cells: one larger daughter cell and one smaller polar body, which degenerates. Secondary oocyte then fuses with the sperm to form diploid zygote.
Follicle Development
The ovarian cycle describes the cyclical development of the follicles in the ovaries. Primary oocyte surrounded by single layer of flat cells (granulosa cells) - Primordial follicle formed. Granulosa cells divide into several layers of cuboidal cells and deposit a layer of clear material around oocyte (zona pellucida) - Primary follicle formed. Fluid spaces (vesicles) form among granulosa cells and the secondary follicle formed. Secondary follicle enlarges, vesicles fuse to form a single fluid-filled chamber (antrum), and the primary oocyte is pushed off to one side - mature of Graafian follicle. Graafian follicle ruptures to release oocyte during ovulation.
Tell me again how much I rely on reproductive system for my paper tomorrow. BIG BIG SIGH.
Which reminds me of which that I need to wake up early to wait for the damned bus (which I have to miss 4 fully-packed ones this morning) and hopefully I wouldn't have to panic like how I did today. ):
Goodnight people.
Seminiferous tubules contains germ cells. Peripheral germ cells are called spermatogonia and actively divides themselves through mitosis and some of the end products are the primary spermatocytes (2N). Primary spermatocytes undergoes the 1st meiotic division to produce 2 secondary spermatocytes. The secondary spermatocytes then undergoes the 2nd meiotic division to produce 2 spermatids. The spermatids then goes through a major transformation to be a spermatozoon, which is sperm cells.
Menses
Progesterone and estrogen levels drops as corpus luteum degenerates. FSH and LH levels drops and the superficial layer of the endometrium is being sloughed off. Menses would lasts for 4 to 5 days.
Proliferative Phase
FSH and LH levels are only slightly elevated through most of the proliferative phase. Developing follicle, due to FSH, releases increasing levels of estrogen near the end of the proliferative phase and sustained high levels of estrogen have positive feedback to FSH and LH. This causes the FSH and LH levels to rise rapidly near the end of the proliferative phase. Estrogen causes the endometrium of the uterus to thicken and develop tube-like glands.
Secretive Phase
FSH and LH levels remain low throughout due to progesterone and estrogen inhibition. Corpus luteum secretes high level of progesterone. Progesterone causes the final development of endometrium and maintains it. Tube-like glands begin to secrete some fluid. If fertilization does not occur, corpus luteum will degenerate after 25 days (day 28) and progesterone levels drops significantly. Superficial layer of endometrium beings to slough off, menses begin.
Ovulation Phase
FSH and LH levels rise rapidly due to the rising levels of estrogen. LH cause final maturation of the follicle and ovulation to occur. Ruptured follicle develops into corpus leteum . Corpus leteum begins secreting large amount of progesterone and some estrogen. Progesterone and estrogen begin inhibiting FSH and LH release. FSH and LH levels drop rapidly after ovulation.
If fertilization occurs, the fusion of sperm (N) and oocyte (N) -> zygote (2N). Zygote undergoes mitosis and becomes an embryo. Implantation of the embryo occurs at the endometrium. Placenta, which is rich in blood supply and is connected to the umbilical cord, forms. Exchanges of nutrients, gases, metabolic wastes between the embryo and the mother takes place there. Lining of the endometrium must be maintained.
Pregnancy = 9 months and 10 days = 118 days.
Trimester = 3 months ; By the third trimester, the baby's head should be at the bottom.
1st Trimester
Placenta releases human chrionic gonadotropin (hCG) and hCG stimulates corpus luteum to secrete progesterone and estrogen.
2nd Trimester
Placenta begins releasing progesterone and estrogen.
3rd Trimester
Placenta completely takes over the corpus leteum in releasing progesterone and estrogen.
Hormonal Regulation
Hypothalamus secretes gonadotropin-releasing (GnRH) hormone that stimulates anterior pituitary gland to release FSH and LH. Testosterone has a negative feelback effect on GnRH, FSH and LH release. Before puberty, testosterone produced in small amounts by testes and adrenal cortex. This inhibits GnRH, FSH and LH secetion. At puberty, hypothalamus and anterior pituitary gland become less sensitive to testosterone inhibition. This results in elevated levels of GnRH, FSH and LH.
Oogenesis
Begins in the foetus. Oogonia (from which oocytes arises) undergo 1st meiotic division but are arrested at prophase I -> Primary oocytes. Primary oocytes remain dormant until puberty. Every month, one primary ooctye is activated and completes 1st meiotic division just before ovulation and the secondary ooctye (daughter cell, large) and polar body (small daughter cell). Secondary oocyte begins the 2nd meiotic division but is arrested at metaphase II. Ovulation occurs and the second oocyte is released. Fertilization occurs when a sperm penetrates the secondary oocyte. Secondary oocyte completes the 2nd meiotic division which gives rise to 2 cells: one larger daughter cell and one smaller polar body, which degenerates. Secondary oocyte then fuses with the sperm to form diploid zygote.
Follicle Development
The ovarian cycle describes the cyclical development of the follicles in the ovaries. Primary oocyte surrounded by single layer of flat cells (granulosa cells) - Primordial follicle formed. Granulosa cells divide into several layers of cuboidal cells and deposit a layer of clear material around oocyte (zona pellucida) - Primary follicle formed. Fluid spaces (vesicles) form among granulosa cells and the secondary follicle formed. Secondary follicle enlarges, vesicles fuse to form a single fluid-filled chamber (antrum), and the primary oocyte is pushed off to one side - mature of Graafian follicle. Graafian follicle ruptures to release oocyte during ovulation.
Tell me again how much I rely on reproductive system for my paper tomorrow. BIG BIG SIGH.
Which reminds me of which that I need to wake up early to wait for the damned bus (which I have to miss 4 fully-packed ones this morning) and hopefully I wouldn't have to panic like how I did today. ):
Goodnight people.
