issues, the broad outlines are reasonably clear and the broad outline is stated below At the beginning of the proliferate

arteries of the endometrium undergo spasm, the cause of the spasm is not clear As a result of the spasm, portions of the endometnum are sloughed out together with the blood, constituting the menstrual flow Usually the superficial 2/3rd of the endometnal tissue is sloughed out. the basal 1 /3rd remains The blood undergoes clotting within the uterine cavity and within the cavity it is liquefied again The blood which comes out per vagina m normal subjects, therefore, does not clot In some individual cases, ovulatton does nol occur, therefore, there is no secretory phase of endomefrium in these women Even then the bleeding occurs, (while the endometnum is still in proliferative phase) Such menstruations are called anoyular menstruation' Hormonal control of menstrual cycle (fig 6 10 4) The different phases of menstrual cycle are controlled by an interplay of a set of hormones Although, till to dale, there are many uncertainties about some issues, the broad outlines are reasonably clear and the broad outline is stated below At the beginning of the proliferate stage, estrogen level is low and FSH level is good Because of This high FSH level, the pnmary follicle matures into a Graafian follicle. The maturing Graafian folhcla is turn secretes estrogen and the ettrogen in turn causes Ihe proliferative change! of the endornitnum 2. The rising level of estrogen causes the LH surge (fig.6 10 4) However. the level of the estrogen must be more than 1,50 pg/ml and duration of this high level must be 36 hr The LH surge in turn causes ovulation and formation of corpus luteum (CL) The CL in turn secretes progesterone and estrogen The high level of luteinizing hormone (LH) maintains the CL (N B The student should note That exact details of LH surge is complicated and unclear The above account is a simplified version! 3 The continued high level of estrogen and progesterone (fig 6 10 4) ultimate
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