Medical brain notes 42

  Reproductive Cycles In the female reproductive cycle, ovulation is fol lowed by menstrual bleeding in a cyclic, predictable sequence. This recurring process is established dur-ing puberty (average age of menarche is 12.43 years) and  continues until the years prior to menopause (average age 51.4 years). Regular ovulatory cycles are usually established by the third year after menarche, and continue until the perimenopause. Therefore, between 15 and 45 years of age, a woman has approximately 30 years of ovulatory reproduc-tive cycles. The reproductive cycles may be interrupted by conditions including pregnancy, lactation, illness, gyneco-logic disorders and endocrine disorders, and exogenous factors such as hormone-based contraceptives and various other medications.   The duration of an adult reproductive cycle, from the begin-ning of one menses to the beginning of the next menses, averages approximately 28 days, with a range of 23 to 35 days, and com-prises three distinc...

  REPRODUCTIVE CYCLE   As discussed, the reproductive cycle is divided into three phases: menstruation and the follicular phase, ovulation, and the luteal phase. These three phases refer to the status of the ovary during the reproductive cycle. In contrast,  whenreferring to the endometrium, the phases of the menstrual cycle are termed the  proliferative  and  secretory phases.   Phase I: Menstruation and the Follicular Phase   The first day of menstrual bleeding is considered day 1 of the men-strual cycle.  When conception does not occur, the involutionof the corpus luteum and, hence, the decline of proges-terone and estrogen levels cause menstruation. Normal menstruation lasts 3 to 7 days, during which women lose 20 to 60 mL of dark, nonclotting blood. Menstruation consists of blood and desquamated superficial endometrial tissues. Prostaglandins in the secretory endometrium and men-strual blood produce contractions of the uterine vasculatur...

  CLINICAL MANIFESTATIONS OF HORMONAL CHANGES   Hormonal changes induced by the hypothalamic-pituitary-ovarian axis and the adrenal gland trigger puberty, and hormones continue to exert a cyclic influence until a woman reaches menopause. At that time, the lack of cyclic ovarian function results in the permanent cessation of menstruation.   Various female structures undergo changes in response to the reproductive cycle hormones: the endometrium and endocervix, breasts, vagina, and the hypothalamus.  Changes in the endo-cervix and breasts can be directly observed. Daily assess-ment of basal body temperature can identify changes in the hypothalamic thermoregulation center. Other changes can be assessed by cytologic examination of a sample from the vaginal epithelium or histologic evaluation of an endome-trial biopsy. A careful history may identify symptoms asso-ciated with hormone effects, such as abdominal bloating, fluid retention, mood and appetite changes, and uteri...