normal menstrual cycle

Question 1

definition

Answer 1

regular occurance of ovulation as a preparation for fertilization and pregnancy during the reproductive life of women

periodic vaginal bleeding that occurs with the shedding of the uterine mucosa is called menstruation with duration 28 days

Question 2

regulation axis

Answer 2

• menstrual blood predominantly arterial, only 25% fr venous origin
• contains tissue debris, prostaglandin and many fibrinolysin fr endometrial tissue
• usual duration is 3 – 5 days but may varies fr 1 day to 8 days
• average blood lost is 30 ml ( vary fr slight spot of blood to 80 ml ); loss of > 80 ml is abN
• amount of blood depends on thickness of endometrium, medications and disease affecting clotting system
• after menstruation, endometrium regenerate fr the stratum basale

Question 3

ovarian cycle

Answer 3

• fr birth, there are many primordial follicles ( PF ) under ovarian capsule
• each PF contains immature ovum

i) at start of cycle, several PF enlage and a cavity forms around ovum (antrum)
- the cavity is filled with follicular fluid

ii) one of the follicles in one ovary starts to grow rapidly and becomes dominant follicle on ≈ 6th day
- whereas the others regress forming atretic follicles
- unknown mech, but DF’s ability to secrete estrogen suspected; thus hormone injections may stimulate follicles dev simultaneously

iii) PF will dev become mature ovarian follicle ( Graafian follicle )
- theca interna of the follicle are the main course of circulating estrogen whereas the high estrogen content in follicular fluid secreted fr granulose cells

iv) about 14th day, the distended follicle rupture; the ovum extruded into abd cavity
- this process is called ovulation
- the ovum is picked up by fimbriated ends of uterine tube ( oviducts ) and transported to uterus
- unless fertilization occurs, ovum degenerates or is passed on thru uterus and out of vagina

v) the ruptured follicle fills with blood, forming corpus hemorrhagicum

vi) the theca cells and granulosa begin to proliferate and blood clot rapidly replaced with luteal cell forming corpus letuem
- this is luteal phase of menstrual cycle, where luteal cell secrete estrogen and progesterone
- growth of CL depend on dev of blood supply ( depend on vascular endothelial growth factor )
- if pregnancy occur, CL persist; if no pregnancy, CL begins to degenerate about 4 days before the next menses ( day 24th of cycle )
- it is eventually replaced by corpus albicans

Question 4

uterine cycle

Answer 4

• is the events occur in uterus during menstrual cycle and terminate in menstrual flow

i) by end of each menstrual period, all but deep layers of endometrium has sloughed

ii) under influence of estrogen fr dev follicles, endometrium regenerates fr the deep layer and increase rapidly in thickness fr 5th to 16th days of menstrual cycle
- as thickness increases, uterine glands are lengthen to prevent coiling or secretion
- these endothelial changes are called proliferative phase / preovulatory or ovulatory phase
- it represent restoration of epithelium fr preceding menstruation

iii) after ovulation, endometrium becomes more highly vascularised and slightly odematous under estrogen and progesterone influence of CL

iv) the glands become coiled and tortuous and they secrete clear fluid.
- thus this phase is called secretory or luteal phase
- it represent preparation of uterus for implantation of fertilized ovum
- its length is constant, 14 days

v) when CL regress, hormonal support for endometrium is withdrawn.
- endometrium become thinner, foci of necrosis appear esp vessel wall of spiral arteries causing spotty hemorrhage that becomes confluent and produce menstrual flow
- vasospasm occurs to stop bleeding, dt action of locally released prostaglandin

Question 5

functional diagnostic tests

Answer 5

For indication of ovulation
i) rise in basal body temperature
- accurate temperature obtained, btw 96 and 100 oF
- women should check temperature, orally, vaginally or rectally in the morning before getting out fr bed
- unknown cause for temperature changes, maybe dt increase progesterone secretion
ii) rise in urinary LH during rise in circulating LH that cause ovulation
- ovulation normally occurs bout 9 hrs after peak of LH surge in midcycle