Flashcards in Menstrual Cycle Deck (20):
What happens in the preparation phase?
Follicles grow in the ovary
Uterus prepares for sperm transport and implantation of the conceptus
Changes occur to facilitate sexual interactions
What are the names of the preparatory phase?
Follicular phase in ovaries
Proliferative phase in the uterus
Other terms for the waiting phase?
What happens in the waiting phase?
Corpus luteum is in the ovary
Changes occur in preparation for pregnancy
Ended by shedding of part of endometrium
What are the gonadal steroids and the gonadotrophins?
Steroids - oestrogen and progesterone
Trophins - LH and FSH
Actions of the gonadotrophins?
-FSH binds to granulosa cells
-LH binds to thecal cells (theca interna)
-LH surge stimulates ovulation
-LH maintains the corpus luteum
Which hormones does the corpus luteum secrete?
Progesterone and a bit of oestrogen
What is the actions of the gonadal steroids in the follicular phase?
Oestrogen stimulate Fallopian tube function
Thickening of endometrium (secretes fluid to support sperm)
Growth and motility of myometrium (muscle contraction - sperm transport)
Changes in skin, hair, metabolism, calcium metabolism
What is the effect of gonadal steroids in the luteal phase?
Progesterone acts on oestrogen primed cells to cause more thickening of endometrium into secretory form
Thickening of myometrium but reduced motility
Thick, acid cervical mucus
Changes in mammary tissue
Increased body temperature
Why is thick, acid cervical mucus produced in the luteal phase?
Protects the uterus from sperm and bacteria - action of contraception
How does the brain monitor the growth of follicles?
The bigger the follicle, the more oestrogen it produces
Why is there high FSH at the start of the menstrual cycle?
Corpus luteum absent, follicles only partially developed
Therefore little secretion of steroids or inhibin so little inhibition at the hypothalamus or anterior pituitary
What does the FSH do at the start?
Binds to granulosa cells, causing follicular development to continue and the theca interna develops
What does the developing follicle start to secrete and what are the effects?
Granulosa cells secrete oestrogen stimulated by LH and inhibin
Inhibin inhibits FSH and no new follicles can develop
The oestrogen exerts positive feedback at the hypothalamus so LH levels rise but FSH cannot due to inhibin
What factors can affect when ovulation occurs?
What happens after ovulation?
Corpus luteum forms spontaneously
Begins to secrete oestrogen and progesterone which maintains suppression of FSH
LH is also suppressed because positive feedback is inhibited by progesterone
What happens in the luteal phase?
Corpus luteum grows and secretes more steroids
After exactly 14 days it dies
What does the death of the corpus luteum cause?
Rapid fall in steroids levels
Relieves inhibition of FSH a
What is the interval between ovulation and menses?
Always 14 days