P-2 Life Processes in Living Organisms Part – 2 — Science STD 10 — Question

(i) Female reproductive system undergoes some changes at puberty and those changes repeat at the interval of every 28 - 30 days. These repetitive changes are called as menstrual cycle.
(ii) Menstrual cycle in a natural process controlled by four hormones. Follicle stimulating hormone (FSH), Luteinizing hormone (LH), estrogen and progesterone.
(iii) One of the several follicles in the ovary starts to develop along with the oocyte present in it, under the effect of follicle stimulating hormone. This developing follicle secrets oestrogen.
(iv) Endometrium of the uterus starts to develop or regenerate under the effect of estrogen.
(v) Meanwhile developing follicle completes its development.
(vi) It bursts under the effect of lutenizing hormone and oocyte is released. This is called as ovulation.
(vii) Remaining tissues of the burst follicle forms the corpus luteum. Corpus luteum starts to secrete progesterone.
(viii) Endometrial glands secrete their secretion under the effect of progesterone. Such endometrium is ready for implantation of embryo.
(ix) If oocyte is not fertilized within 24 hours, corpus luteum becomes inactive and transforms into corpus albicans.
(x) Endometrium starts to degenerate in absence of estrogen and progesterone.
(xi) Tissues of degenerating endometrium and unfertilized ovum are discarded out through vagina, accompanied by bleeding.
(xii) Bleeding continues approximately for 5 days. This is called mensturation.