月经周期
The female reproductive system is a wonderfully complex system involving continuous communication between the brain centers and the ovary. 下丘脑分泌的激素, the pituitary and the ovary are the messengers that regulate the monthly cycle.
下丘脑和脑垂体
The hypothalamus is located centrally in the brain and communicates by way of an exchange of blood with the pituitary gland. Several neuroendocrine agents, or hormones, are produced by the hypothalamus. The most important hormone for reproduction is called gonadotropin releasing hormone, 也就是GnRH. It is released in a rhythmic fashion every 60 to 120 minutes.
GnRH stimulates the pituitary gland to produce follicle stimulating hormone (FSH), the hormone responsible for starting follicle (egg) development and causing the level of estrogen, 主要的雌性激素, 上升. 促亮氨酸激素, 另一种生殖垂体激素, aids in egg maturation and provides the hormonal trigger to cause ovulation and the release of eggs from the ovary.
卵巢
The main function of the ovaries is the production of eggs and hormones. At birth, the ovaries contain several million immature eggs. 不会产生新的卵子. These eggs are constantly undergoing a process of development and loss. 大多数人还没有成熟就会死去. This process of egg loss occurs at all times, 包括出生前, before puberty and while on birth control pills. 卵巢 undergoes a constant process of egg depletion throughout its lifetime.
As the levels of FSH and LH in the blood increase with puberty, the eggs begin to mature and a collection of fluid — the follicle — begins to develop around each one.
The first day of menses is identified as cycle day one. 雌激素处于低点. 因此, 垂体分泌FSH和LH, a process which actually begins before the onset of your menses. These hormones in turn stimulate the growth of several ovarian follicles, each containing one egg. The number of follicles in the monthly "cohort" of developing follicles is unique to each individual. One follicle will soon begin to grow faster than others. 这被称为显性卵泡.
As the follicle grows, blood levels of estrogen rise significantly by cycle day seven. This increase in estrogen begins to inhibit the secretion of FSH. The fall in FSH allows smaller follicles to die off. 实际上,他们“缺乏”FSH.
排卵
When the level of estrogen is sufficiently high, 会产生LH的突然释放, 通常在月经周期的第13天左右. This LH peak triggers a complex set of events within the follicles that 结果 in the final maturation of the egg and follicular collapse with egg extrusion. 排卵 takes place 28 to 36 hours after the onset of the LH surge and 10 to 12 hours after LH reaches its peak.
The cells in the ovarian follicle that are left behind after ovulation undergo a transformation and become the corpus luteum. 除了雌激素, they now produce high amounts of progesterone to prepare the lining of the uterus for implantation.
黄体期
黄体期, 或者是月经周期的后半段, begins with ovulation and lasts approximately 14 days — typically 12 to 15 days.
在此期间, changes occur that will support the fertilized egg, 哪个叫做胚胎, 应该 怀孕 结果. The hormone responsible for these changes is progesterone, which is manufactured by the corpus luteum. 在黄体酮的作用下, the uterus begins to create a highly vascularized bed for a fertilized egg.
If a 怀孕 occurs, the corpus luteum produces progesterone until about 10 weeks gestation. 否则, 如果没有胚胎植入, the circulating levels of hormone decline with the degeneration of the corpus luteum and the shedding of the lining of the uterus (endometrium), 导致出血.
子宫
The lining of the uterus, or endometrium, prepares each month for the implantation of an embryo. This preparation occurs under the influence of estrogen and progesterone from the ovary. 如果没有怀孕, the endometrium is shed as a menstrual period, 大约在排卵后14天.
加州大学旧金山分校健康 medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.