MENSTRUAL CYCLE
Menstruation – periodic uterine bleeding in response to cyclic hormonal changes
- refers mainly to changes in uterus and ovaries which recur cyclically from the time of menarche to menopause (physiological end of menstrual cycle)
- shedding off of endometrial lining
- average: 28days (+/- 5-10 days)
- duration: 2-8 days bleeding episodes
- average blood loss: 30ml of blood
- loss of Fe averaging 0.5mg to 1mg daily
Estrogen – very high when ovulating
Progesterone – increase if ever during ovulation there is fertilization; needed for pregnancy
Pre – menstrual syndrome – because of the play of hormones
4 Phases of Menstrual Cycle:
a). Menstrual Phase – characterized by shedding of the endometrium with the discharge exiting through the vagina
- prostaglandin content of the endometrium reaches its highest levels
- estrogen and progesterone levels are relatively low, which stimulates the release of FSH
- combined with a steady low level of LH secretion, ovarian estrogen secretion begins
b). Follicular (ovary) or Proliferative (endometrium)
- endometrium regenerates and thickens in preparation for possible implantation
- rising blood levels of estradiol exert negative feedback on FSH secretion and positive feedback on LH secretion
- ovulation begins
- ovum remains viable for 24 – 46 hours
c). Luteal (ovary) or Secretory (endometrium)
- begins after ovulation and is relatively finite period of about 12 – 14 days
- under continuing LH secretion, a temporary endocrine gland is formed (corpus luteum) from the ruptured follicle
- progesterone and estrogen levels drop, the negative feedback effect of estrogen on FSH ceases
d). Ischemic Phase – blood vessels rupture
- endometrium becomes pale
