03. Menstruation Flashcards
Two general phases of Menstrual & Ovulatory Cycles
Follicular phase & Luteal phase
Hormone surges during Follicular Phase (in order)
FSH & LH (minor surge); Estrogen surge; LH surge; FSH surge
Hormone surges during Luteal Phase (in order)
Progesterone (major) & Estrogen (minor surge)
Follicular Phase Characteristics
Begins at onset of menses; Ovarian follicle recruitment & maturation; Ends with pre-ovulatory surge of LH stimulating ovulation (24-36 hr at end)
Luteal Phase Characteristics
Begins with ovulation; Ends at onset of menses; Endometrium thickens in preparation for pregnancy; Ends in pregnancy or luteolysis
Estimated blood loss during menses
~30 cc
Excessive blood loss during menses
~80 cc
Period of heaviest blood loss during menses
First 2 days
FSH effects
Causes 15-20 eggs to begin maturing in each ovary; Follicles produce estrogen
Estrogen effects
Released by maturing follicles; when threshold is reached, follicle is mature and triggers LH surge
LH Effects
Triggered by high estrogen levels; Causes egg to burst from follicle; Stimulates ovary to produce progesterone after ovulation. Also stimulates follicles to produce androgens, which are converted to estrogen
Progesterone Effects
Produced by corpus luteum; Prevents release of all other eggs for that cycle; Causes thickening of endometrium & sustains life until corpus luteum distintegrates (12-16 days later); Causes changes in 3 fertility signs
What are the 3 fertility signs?
Change in temperature, cervical fluid, and cervical position
3 Major Components that Regulate the Menstrual Cycle
Hypothalamic/Pituitary Axis; Ovaries; Endometrium/Uterus
5 Small Peptides/Amines From Hypothalamus that affect Reproductive Cycle
GnRH; TRH; SRIF; CRF; PIF (Prolactin release-inhibitin factor)
GnRH Effects
Pulsatile release from hypothalamus; Increased during follicular phase; Decreased during luteal phase; Pulses q90min; To the ANTERIOR PITUITARY via portal circulation;
Negative Estrogen Feedback Mechanism
During early follicular phases, estrogen levels low
Positive Estrogen Feedback Mechanism
High concentrations at end of follicular phase trigger FSH & LH, which trigger increased estrogen release; Ensuring LH surge triggers ovulation
Follicle count of 20 week fetus
6 million
Follicle count of newborn
600,000
Follicle count at menarche
300,000
Follicle count at menopause
10,000
FSH & LH negative feedback
High levels of estrogen and progesterone during luteal phase suppress FSH & LH
What is the time span between the LH surge and ovulation?
24-36 hr