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Question : After puberty human female shows cyclic changes in her reproductive system . Explain structural and hormonal changes in the uterus . |
Answer» Solution :T.S. of Ovary :  2. Menstrual cycle. (1) Menstrual cycle starts withmenarcheand ends withmeno pause. It lasts forabout 28 days and is repeated throught this period with exception of duration of pregnancy. (2) There are series of changes in uterusand ovariesduring themensturalcycle andthese changes are regulatedby gonadotropinhormonesfrom pituitary and hormones of ovary. (3) Hormones, FSH, LH. estrogenand progesterone are respon-sible for these cyclic changes in mature females. (4) Menstrual cycle is dividedinto four phases , viz., menstrual phase, proliferative phase (in uterus)or follicularphase (in ovary),ovulatory phase,secretoryphase (in uterus)or luteal phase (in ovary). (1) Menstural phase : Menstrual phase 1st to 4th day in the absence of fertilization.During this phase bleeding occursas the endometrium of uterusis sloughed off. The thicknessof endometrium becomes 1 mm.After about 4th day of bleeding, once againthe FSH secretionfrom the pituitaryis resumedand the new follicle starts developing. (2)Follicular phase (in ovary)or Proliferativephase (inuterus) : (i) OVARIAN chanes : When the ovaryis in follicularphase, the uterusentersin proliferative phase.This takesplacefrom 5thto 13th day of the cycle. During this phase the new primordial follicle in theovary developsdue to theactionof FSHfrom pituitary. Primordial folliclegraduallychangesinto Graafian follicle, producingthe HORMONE estrogen.Only one follicledevelops in one cycle. (ii) Uterine changes : Theuterus also undergoes proliferation. The endometrial glands of uterusare stimulated and repairprocess of the uterustakes place under tehinfulence of estrogen.The thicnkessof endometrium growsto about 3 mm to 5 mm. (3) Ovulatory phase :Ovulation takes place, onthe 14 th day ofthe cycle. The matureGraffian follicle rupturesdue to LH secreted by the pituitary.The ovumis released in abdominal cavity. This ovum is pickedup by the fimbrineof infundibulum of fallopian tube. It passes throughthe fallopian tube. On its way if it happens to meet sperm, it is fertilized. If unfertilized , the ovumdegenerates. (4)Luteal phase (Ovary) or Secretory phase (Uterus) : Luteal phase in the ovarycorresponds with the secretoryphase in theuterus . It takes place between15th to 28th day of the cycle. (i) Ovarian changes : In the ovary thecourpus luteumis formed from the empty Graffianfollicle. The corpus luteum PRODUCES progestrone. If ovum is fertilizedthe corpuslutuemis retained. Hormones LH and LTH from pituitary help in the maintanceof corpus luteum. If the ovum is ot fertilized , the corpusluteum degenerates and formscorpusalbicans. (ii) Uterine changes : Under the INFLUENCE of progesterone, ther is increase in the thicnkess of endometrium. Endometrial glandsgrow and become secretory. Thehormone progesterone is responsiblefor the maintenance of pregnancy. If fertilized ovum reaches the uterus. If is implanted and placenta is formed. Thisleadsto pregnancyTill placenta becomes functionalthe corpus luteumkeeps on producing progesterone. If progesterone sourceis cut off, the endometrium sloughs off and themensturation begins, as in case of no conception. |
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