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Menstrual cycle The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the ...
Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and after the follicular phase. Ovulation is stimulated by an increase in luteinizing hormone (LH).
At the end of the luteal phase, progesterone levels fall and the corpus luteum atrophies. The drop in progesterone leads to endometrial ischemia which will subsequently shed in the beginning of the next cycle at the start of menses. [1] This last stage in the luteal or secretory phase may be called the ischemic phase and lasts just for one or ...
During the secretory phase, the uterine glands become very coiled with wide lumens and produce a glycogen-rich secretion known as histotroph or uterine milk. [ 1 ] [ 2 ] This change corresponds with an increase in blood flow to spiral arteries due to increased progesterone secretion from the corpus luteum .
The corpus luteum develops from an ovarian follicle during the luteal phase of the menstrual cycle or oestrous cycle, following the release of a secondary oocyte from the follicle during ovulation. The follicle first forms a corpus hemorrhagicum before it becomes a corpus luteum, but the term refers to the visible collection of blood, left ...
An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries.It secretes hormones that influence stages of the menstrual cycle.In humans, women have approximately 200,000 to 300,000 follicles at the time of puberty, [1] [2] each with the potential to release an egg cell (ovum) at ovulation for fertilization. [3]
However, once ovulation occurs, the ovary (specifically the corpus luteum) will produce much larger amounts of progesterone. This changes the proliferative pattern of the endometrium to a secretory lining. Eventually, the secretory lining provides a hospitable environment for one or more blastocysts.
If conception does not occur, decreasing excretion of progesterone will allow the hypothalamus to restart secretion of GnRH. These hormone levels also control the uterine (menstrual) cycle causing the proliferation phase in preparation for ovulation, the secretory phase after ovulation, and menstruation when conception does not occur.