endometnum continuously proliferates and hence this phase is called the proliferate phase After the ovulaiion

and other organs, (iii) side by side the maturation of follicle m the ovary (ovarian cycle) continues The first day of bleeding is counted as the first day of the menstrual cycle In an 'average' cycle, the bleeding stops on about 4th day From the day of stopping of the bleeding (say the 4th day) till the day of ovulation (which is usually on the 14th day of the menstrual cycle). the endometnum continuously proliferates and hence this phase is called the proliferate phase After the ovulaiion. for a period of another 14 days, the proliferation stops, but the glands of the endometnum become filled with secretion, so that this phase is called secretory phase Diagrammatically the phases can be shown as in fig 6 10 3 Changes in proliferative phase fig 6 10 4) Uterus (a) Ertdometnum Just after the cessation of menstrual bleeding, the endometnum [the mucous membrane of the uterus) is thinnest (because all the superficial layers have been cast off during the menstrual bleeding) The endometrium is little more than 1 mm thick at this stage The glands of the endometnum are simple tubular glands As the proliferative stage progresses, the following changes in endometnum occur. (i) Glands grow in Length, (ii) epithelial cells of the endometnum proliferate, [iii] growth of the endometnal stroma occurs and (iv) the blood vessels grow Just before ovulation (i e . on the 14th day), the endomelnum becomes about 5 mm thick Fig 6 10.3 Time courses in different phases of menstrual cycle (b) Endocervical mucus The secretion of the glands of the uterine cervix becomes vary thin at the stage of ovulation to facilitate the entry of the sperms (c) Uterine muscle The myometnal contractions become more powerful This powerful contraction probably produces a suction action by which the spermatozoa are drawn inside the uterus II Changes in the ovary Side by side, the ovarian cycle is progressing. Duong the proliferative phase an immature follicle is ripening into a Graafian follicle Cause of the changes The uterine changes are due to the rising concentration of estrogen Because of the fact that the proliferate phase is associated with a growing (maturing) follicle in the ovary, this phase is also called 'follicular phase' Changes m secretory phase (fig 6 10 4] With in about three days after the ovulation. the corpus luteum is well developed, with a diameter of about 1 cm and it is now sacreting progesterone The changes in the secretory phase are due to Ihe progeslerona hence it is also called progesteronal phase I The utenne changes are (i) Uterine glands become. tortuous and filled with secretions Some exudating of secretion may occur from the endametnum, which escapes from the vagina and called 'uterine milk' (ii) The arteries of the endometrium become coiled (iii) Glycogen content of the endometrial epithelium increases (iv) The imtability of the myometnum decreases (and so. the uterus becomes quiet i e , non contracting The secretion of the glands of uterine cervix becomes much thicker at this stage, so thai, paih of the sperm is blocked (As a result, cortus at this stage, from the point of view of centraception. is safe) II Ovarian changes Corpus luteum is formed, (ii) granulosa cells are converted into lutein cells Unless pregnancy occurs, the corpus luteum degenerates on 14th day (the day of ovulation being the first day) Secretory (progesteronal) phase is also called luteal (from corpus luteum) phase, for obvious reasons Fig 6 10 4 To show the changing hormonal levels in different phases of menstrual cycle For the numerical values of the hormones, see appendix at the back of this section. Changes in the bleeding phase Uterus At the end of the secretory phase, the spiral