Female Reproductive Cycles PDF

FEMALE REPRODUCTIVE CYCLES By Dr. Haidy Refaat  FEMALE REPRODUCTIVE CYCLES At puberty, the female begins to undergo regular monthly cycles known as reproductive or sexual cycles. These cycles are controlled by the hypothalamus. Cells of the anterior pit...

FEMALE REPRODUCTIVE CYCLES By Dr. Haidy Refaat  FEMALE REPRODUCTIVE CYCLES At puberty, the female begins to undergo regular monthly cycles known as reproductive or sexual cycles. These cycles are controlled by the hypothalamus. Cells of the anterior pituitary gland start to secrete gonadotrophines; follicle stimulating hormone (FSH) and lutinizing hormone (LH). FSH and LH stimulate and control cyclic changes of the ovary (ovarian cycle). FSH and LH stimulate the ovary to secrete estrogen and progesterone hormones. Changes in estrogen and progesterone levels cause cyclic changes in the uterus (menstrual cycle). LH surge is needed to induce ovulation. The ovarian and menstrual cycles begin at puberty; continue on monthly basis throughout the fertile life of female and cease after menopause. Fertile life of female extends from 13 up to 48 years. Menarche is the first menstrual cycle.  OVARIAN Ovarian cycle CYCLE Definition: The ovarian cycle is the monthly changes which occur in the ovary of a fertile female. Duration: 4 weeks Phases: 1) FOLLICULAR PHASE 2) OVULATION 3)LUTEAL PHASE. 1) FOLLICULAR PHASE Under the influence of FSH a number of ovarian follicles (5-15 follicles) grow, but only one reaches full maturity, the others degenerate and become atretic.. 5-15 primordial follicles begin to grow and the follicular cells become cuboidal. At this stage the follicles are called primary follicles. The follicular cells divide to form many layers of cells around the ovum. A glycoprotein shell called zona pellucida is interposed between the oocyte and the follicular cells Ovarian stroma cells form a capsule around the follicle named theca. Theca is of two layers; theca interna is vascular and contains secretory cells, theca externa is formed of connective tissue and fibroblast like cells.  Follicular (granulosa) cells secrete fluid rich in glycoprotein in between the cells. The entire follicle is called secondary follicle. Follicular and theca cells increase in number. The follicle becomes so large (15 mm) that it occupies most of the width of the ovary. It forms avascular spot, on the surface of the ovary. The follicle is now termed tertiary or mature (Graffian) follicle. Growth of the fluid inside its cavity pushes the ovum to one side of the follicle where it rests on cumulus oophorus. The ovum is closely surrounded by columnar cells named corona radiata. Mature graffian follicle 2) OVULATION Definition: Ovulation is rupture of the mature Graffian follicle and liberation of the oocyte into the peritoneal cavity. Mechanism: The secondary oocyte with corona radiata and liquor folliculi. Expulsion of the oocyte is the result of 1- increased intra-follicular pressure 2- contraction of the smooth muscles in the theca externa stimulated by prostaglandins. 3-Enzymatic digestion of the follicular wall is one of the mechanisms leading to ovulation. Ovulation is triggered by LH surge. Ovulation follows LH peak by 12-24 hours. LH surge resumes the first meiotic division of the primary oocyte. Timing: Ovulation occurs at the midcycle; day 14 of a 28 days menstrual cycle. Oocyte transport Shortly before ovulation, fimbriae of the fallopian tube cover the surface of the ovary. Once the secondary oocyte lies free in the peritoneal cavity it is sucked into the infundibulum of the tube Ovum vitality: The ovum which is 140 micron remains fertilizable for 12 hours after ovulation. 3) LUTEAL PHASE Following ovulation the walls of the ovarian follicle and theca folliculi collapse. The ruptured follicle undergoes a process of lutinization to form a corpus luteum.. The corpus luteum continues to secrete estrogen and progesterone for about 12 days. If pregnancy does not occur the corpus luteum will degenerates. It is now called corpus albicans.  If pregnancy does occur, HCG produced by the syncytiotrophoblast(future placenta) will support the corpus luteum which enlarges and continues to secrete its hormones for 20 weeks (end of the 4th month of pregnancy). It is called corpus luteum of pregnancy and is one-third to one-half the size of the ovary. After the 4th month the luteal cells regress as secretion of progesterone by the placenta becomes adequate to maintain pregnancy.  MENSTRUAL (UTERINE) CYCLE Definition: Menstrual cycle is the cyclical changes which occur in the endometrium of the uterus of fertile female. These changes aim at preparation of the endometrium to receive a fertilized ovum. Duration: 28 days. The cycle may vary from female to female or from cycle to cycle in the same female. Phases : The menstrual cycle is divided into three phases; mensis (bleeding or menstrual) phase, proliferative phase and secretory phase. Phases of uterine cycle matching phases of ovarian cycle and hormonal controls 1) BLEEDING (MENSIS OR MENSTRUAL) PHASE The average bleeding phase is 5 days (from 3-7days). By the end of this phase thickness of the endometrium is 0.5 mm. The first day of bleeding is counted as the beginning of each menstrual cycle (day 1). 2) PROLIFERATIVE (ESTROGENIC OR FOLLICULAR) PHASE Duration: 9 days. Proliferative phase is controlled by estrogen hormone secreted by the ovarian follicles. It starts with repair (early proliferation) of the denuded surface from the basal parts of the endometrial glands which were not shed by menstruation. The endometrium becomes more vascular and its thickness reaches 3 mm. This phase is called follicular because the ovarian follicles are developing during it. 3) SECRETORY (LUTEAL OR PROGESTATIONAL) PHASE Duration: 14 days. Secretory phase is controlled by progesterone hormone secreted by the corpus luteum. It is called luteal because it coincides with formation, growth and function of the corpus luteum. Epithelial cells increase in size, and the endometrial glands become tortous, wide and saccular. The uterine glands become distended with secretions. Vascularity increases and large lacunae develop.. Thickness of endometrium reaches 5 mm. It is the phase favorable for implantation of the blastocyst. If pregnancy about on day 20 of the menstrual cycle), the thick endometrium is maintained by progesterone secreted by corpus luteum (upto the 4th month of pregnancy), If pregnancy does not occur, the corpus luteum degenerates and levels of progesterone and estrogen are lowered and the secretory endometrium enters an ischemic phase. Rupture of the damaged vessels follow and blood sweeps into the surrounding tissues. As small pieces of endometrium detach and pass into the uterine cavity, the torn ends of vessels bleed into the uterine cavity resulting in loss of about 60 ml of blood. Clinical notes -Menopause Definition: the time in woman’s life when cyclic functions of ovaries and menstrual periods cease. Timing: The average age is about 50 year but many occur earlier. Mechanism: Ovaries become less responsive to stimulation by FSH and LH. Consequently, ovaries secrete small amount of estrogen and progesterone and egg release stops. Symptoms: : Hot flashes in the head and neck, symptoms such as fatigue, irritability, insomnia and nervousness, Dizziness, tingling sensation Treatment: estrogen replacement therapy.