Menstrual cycle is characterized by discharge of blood and tissue debris(menses)from the uterus every 28 days.This is due to the breakdown of the endometrium which occurs when the level of progesterone falls and the girl starts to menstruate.The follicle stimulating hormone (FSH)causes the Graafian follicle to develop and also stimulate the ovary to release oestrogen.Oestrogen hormone triggers the onset of secondary sexual characteristics.Luteinising hormone (L.H)causes the mature ovum to be released from the Graafian follicle a process called ovulation. After ovulation progesterone hormone is produced.
•After menstruation,the anterior lobe of the pituitary gland starts secreting the follicle stimulating hormone (F.S.H) which causes the Graafian follicle to develop in the ovary.It also stimulates the ovary tissues to secrete oestrogen.
•Oestrogen brings about the repair and healing of the inner lining if the uterus(endometrium) which had been destroyed during menstruation.
•Oestrogen level stimulates the pituitary gland to produce (Luteinising Hormone (L.H) ).This hormone makes the mature Graafian follicle to release the ovum into the funnel of oviduct a process called ovulation.
After releasing the ovum,the Graafian follicle changes into a yellow body called corpus luteum.
The Luteinising hormone stimulates the corpus luteum to secrete a hormone called progesterone which stimulates the thickening and vascularization of endometrium. This prepares the uterine wall for implantation of the blastocyst.
If fertilisation takes place,the level of progesterone increases and thus inhibits FSH from stimulating the maturation of another Graafian follicle.
If fertilisation does not occur,the corpus luteum disintegrates and the level of progesterone goes down.The endometrium sloughs off and menstruation occurs.
Belan answered the question on March 23, 2019 at 14:57
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