Flashcards in Normal Menstrual Cycle Deck (35):
What are the 3 main phases of the ovarian cycle?
1. Follicular phase
3. Luteal phase
What controls endometrial changes?
The ovarian cycle
How long does the average ovarian cycle lasts?
What length is the luteal phase?
It is always 14 days
For a normal menstrual cycle to occur, what must there be?
*Intact hypothalamo-pituitary-ovarian endocrine axis
*Presence of responsive follicles in the ovaries
What does the hypothalamus act on? What does the hypothalamus secrete to do this?
It acts on the pituitary gland by secreting Gonadotropin-releasing hormone (GnRH)
When stimulated by the hypothalamus, what does the pituitary secrete?
*Follicle stimulating hormone (FSH)
*Luteinising Hormone (LH
What is the function of oestradiol? Why is it important?
*Suppresses FSH and LH secretion in a negative feedback loop
*Means only one follicle and oocyte mature
*Reaches threshold level which converself causes sudden spike in LH
*Also causes endometrium to reform and become 'proliferative' (thickens)
What does the follicle from which the egg was released become?
What does the corpus luteum produce?
What does progesterone do in the menstrual cycle? Cause what?
*Stromal cells of endometrium enlarge, glands swell and blood supply increases
Luteal phase rise:
*Endometrium becoming receptive to implantation of the blastocyst
*Increased production of eostrogen by the adrenal glands
*Negative feedback causing decreased LH and FSH (needed to maintain corpus luteum
*Increase in the woman's basal body temperature
What maintain a corpus luteum?
*thromphoblast secretes hCG which maintains the corpus luteum
What happens in the follicular phase days 1-8 of the ovarian cycle?
*Start FSH and LH rise in response to the fall in oestrogen and progesterone at the start of menstruation
*FSH stimulates development of follicles and one follicle becomes dominant
What happens in the follicular phase days 9-14 of the ovarian cycle?
*The follicle increases in size and matures
*the granulosa cells of the follicle produce oestrogen
*as oestrogen rises the release of LH and FSH is suppressed in a negative feedback loop
What happens in the ovulation phase of the ovarian cycle?
*Immediately before ovulation oestradiol levels fall and progesterone rises
*oestrogen levels reach threshold resulting in surge of LH
*LH Surge causing ovulation within 18hour after
*The follicle rupture and the oocyte is extruded
What are ovarian hormones?
Oestrogen and progesterone
What are pituitary hormones?
LH and FSH
What happens in the luteal phase of the ovarian cycle? (days 15-28)
*FSH and LH cause remaining Graafian follicle to develop into corpus luteum
*Corpus luteum major source of progesterone
*LH and FSH remain low until corpus luteum regresses, as they are inhibited
*corpus luteum response appropriately to whether conception has occured or not
What happens to the corpus luteum if conception occurs?
*It does not regress, it is maintained by hCG secretions from the trophoblast
What happens to the corpus luteum if conception does not occur?
*It regresses due to fall in FSH and LH
*progesterone levels falls
*fall in progesterone allows FHS and LH to rise and initiate next cycle
It terms of describing the menstrual cycle in what happens to the uterus, what are the 3 phases called?
What happens in the proliferative phase of the uterine cycle?
*During the follicular phase in the ovary, the endometrium is exposed to oestrogen secretion
*this helps to repair and regenerate the endometrium after the previous menstruation
*Increased endometrial thickness
*Development of increased number of secretory glands
What happens in the secretory phase of the uterine cycle?
*After ovulation, progesterone production induces secretory changes in the endometrial glands
*Prepares the endometrium for implantation
What happens in the menstrual phase of the uterine cycle?
*Luteal phase last 14 days
*At the end of the regression of the corpus luteum is associated with decrease in progesterone
*Fall in progesterone causes spiral arteries to contact
*loss of blood supply causes functional endometrium to become ischaemia and necrotic resulting in the endometrium shedding
*3-5day period of menstruation
Main jobs of FSH?
*Binds to ovaries
*Stimulates follicular activity and development
*Thus promoting oestradiol production from dominant follicle for granulosa cells
*Stimulates ovaries to secrete inhibin
Main jobs of LH?
*Binds to the ovaries
*Triggers release of egg from dominant follicle
*Promotes conversion of Graafian follicle into progesterone producing corpus luteum
What are the endometrial changes controlled by?
What causes negative feedback on the pituitary and hypothalamus? What does this result in?
*Results in reduction of GnRH, FHS and LH
The 1st follicle reaching full maturity is called the what? What develops in this?
*Oocyte develops in this
What does oestrogen do?
*Thinning of the cervical mucus to allow easier passage of sperm
*Oestrogen initially inhibits LH productions from pituitary
When does oestrogen reach a threshold level? What does this cause?
*When the ovum is mature
*This conversely causes a sudden spike in LH around day 12
What exactly happens when there is an LH surge?
*Membrane of Graafian follicle becomes thing
*24/48hrs the follicle rupture releasing secondary oocyte
*Occyte quickly matures into ootid and then mature ovum
*Ovum released into peritoneal space and taken into fallopian tube via fimbriae
After conception, what takes over the job of the corpus luteum for producing progesterone? When does this happen?
When is a woman most fertile?
*5 days before ovulation until 1 to 2 days after