1. Menstrual Cycle

2. Menstruation is also called Menstrual bleeding, Menses, a period. The flow of menses normally serves as a sign that a woman has not become pregnant. Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal). The menstrual fluid is largely a mixture of blood and tissue from the uterine lining (Endometrium). The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal.

3. Gonads. Male gonad and Female gonad. Gametes. Spermatozoa (Spermatozoon). Ova (Ovum). Gametogenesis: spermatogenesis Oogenesis

6.  During the reproductive years, failure to menstruate may provide the first indication to a woman that she may have become pregnant.  Gametogenesis in females (Oogenesis) is initiated in the fetus but is immediately arrested and does not commence until puberty when a single oocyte (usually) in alternating ovaries responds to a surge of gonadotropins once a month until menopause at about the age of 45 to 50.

7. Human Menstrual cycle ~28 days in length Includes menses for 3 to 5 days. Ovulation occurs spontaneously Cycles occur throughout the year One egg produced / month Three phases: ◦ Follicular phase (proliferative, estrogenic) ◦ Luteal phase (secretory, progestational) ◦ Menstrual phase (destructive)

8. To understand the menstrual cycle, it is necessary to know the structure of the uterus. The wall of the uterus is made up of three layers. 1. The outermost layer or perimetrium is made up of peritoneum. 2. The main thickness of the wall is made up of smooth muscle. This is the myometrium. 3. The innermost layer (corresponding to mucous membrane) is called the endometrium. It is this layer which undergoes changes during the menstrual cycle.

10. The constituents of the endometrium are as follows: The surface of the endometrium is covered by a lining of epithelium. The stroma fills the interval between surface epithelium and myometrium. It contains numerous simple tubular glands (uterine glands). The arteries that supply the endometrium tend to run vertically towards the surface. Some of these run spirally and supply the whole thickness of the endometrium, while others that remain straight are confined to the basal part.

12. Stages of the menstrual cycle The menstrual cycle has three stages. Viz: Follicular/ estrogenic/ proliferative stage Luteal/ secretory stage Menstrual / ischemic stage Note: The stages of the menstrual cycle run parallel to the ovarian cycle

13. Follicular phase It constitutes the 1 st half of the menstrual cycle. Begins on last day of menses Phase lasts until ovulation (~day 14) In the ovaries follicles grow, secrete increasing amounts of estrogen. During most of this phase, estrogen exerts “negative feedback”. By days 10-12, a few ripe tertiary follicles exist By day 13, 1 Graffian follicle is present In the uterus, the endometrium thickens; uterine glands enlarge, uterine blood supply increases

14. Ovulation Shedding of the ovum from the ovary is called ovulation. occurs at end of follicular phase (day 14) Triggered by peak in estrogen (days 12-13; “positive feedback”) Estrogen causes GnRH surge, LH surge estrogen also “primes” (sensitizes) pituitary gland to GnRH FSH surge also occurs LH surge initiates meiosis in oocyte of Graafian follicle (now a preovulatory follicle) LH also triggers ovulation (9-12 hrs after LH surge peaks) other antral follicles doomed to atresia

17. Luteal phase Last half of menstrual cycle (~14 days) Follicle is transformed to corpus luteum (CL) by LH surge CL secretes progesterone, oestrogen(very little amounts) High progesterone, estrogen exert negative feedback on hypothalamus Uterine lining becomes thick, spongy LH, FSH levels are negligible > atresia If fertilization takes place and conceptus implants, placental hCG rescues corpus luteum No hCG(human chorionic gonadotrophin) > menstrual phase

19. Menstrual phase 4-5 days in length uterine lining degenerates follicle development continues ◦ several antral follicles exist ◦ follicles stimulated by LH, FSH pulses ◦ estrogen levels in blood begin to rise

21. Post menstrual Proliferative Menstrual Secretory LUTEAL PHASE FOLLIC -ULAR PHASE 1 TO 4 DAYS– MENSTRUAL PHASE, 5 TO 8 DAYS- POST MENSTRUAL PHASE, 9 TO 17 DAYS- PROLIFERATIVE PHASE, 20 TO 28 DAYS- SECRETORY PHASE. OVULATION BEGINS BETWEEN 14 AND 15 TH DAY CORPUS LUTEUM BEGINS TO DEGENERATE BETWEEN 24 TO 25 TH DAY

22. Name of phase Average start day assuming a 28-day cycle Average end day menstrual phase14 follicular phase (also known as proliferative phase) 513 ovulation (not a phase, but an event dividing phases) 14 luteal phase (also known as secretory phase) 1526 ischemic phase (some sources group this with secretory phase) 2728

27. Few Terms Infrequent or irregular ovulation is called Oligoovulation. The absence of ovulation is called Anovulation. Normal menstrual flow can occur without ovulation preceding it: an anovulatory cycle. Anovulatory cycles commonly occur prior to menopause (perimenopause) and in women with polycystic ovary syndrome. Very little flow (less than 10ml) is called Hypomenorrhea.

28. Regular cycles with intervals of 21 days or fewer are Polymenorrhea. Frequent but irregular menstruation is known as Metrorrhagia. Sudden heavy flows or amounts in excess of 80 ml are termed Menorrhagia. Heavy menstruation that occurs frequently and irregularly is Menometrorrhagia. The term for cycles with intervals exceeding 35 days is Oligomenorrhea. Amenorrhea refers to more than three to six months without menses (in the absence of pregnancy) during a woman's reproductive years.