Repro 2.2 The Menstrual Cycle Flashcards
What is the reproductive cycle?
A series fo physiological changes surrounding ovulation
What purpose of the first phase of the reproductive cycle?
The ovaries, reproductive tract and other systems are prepared for ovulation so to maximise the chance of fertilisation
What is the purpose of the waiting phase?
If fertilisation occurs, the conceptus is initially too small to signal its presence so the waiting phase allows time for an appropriate chemical signal from the developing placenta during which physiological changes occur in preparation for a potential pregnancy
WHat are the phases of the menstrual cycle?
The initial phase is known as the follicular or proliferative phase
The waiting phase is the luteal or secretory phase
What coordinates the phases of the menstrual cycle?
Gonadotrophins and gonadal steroids
When is the menstrual cycle deemed to begin?
The first day of the menstrual bleed although this is physiologically the end of the previous cycle
How long are the phases?
Follicular - usually 12-14 days but variable
Luteal - 14 days exactly
How is the early follicular phase characterised? (relative levels of hormones)
High titres of FSH and LH
Low but rising titres of oestradiol
Very low levels of progesterone
What are the relative levels of hormones in the later follicular phase and what results?
FSH levels fall
LH levels rise
Oestrogen levels rise dramatically - this is followed by the LH surge and ovulation
What are the relative levels of hormones in the early luteal phase?
Low FSH and LH
Rising titres of oestradiol and progesterone
What are the relative levels of hormones in the late luteal phase?
Low FSH and LH
High oestradiol and progesterone (progesterone higher)
What happens to the hormone levels at the end of the luteal phase and what is the result?
Progesterone then oestrogen titres fall and menstruation begins (progesterone lower)
What effects do the rising titres of oestrogen have on the fallopian tubes?
Stimulate secretion and muscular contraction
Growth and motility of fallopian cillia
What effects do the rising titres of oestrogen have on the myometrium?
Stimulate growth and motility
What effects do the rising titres of oestrogen have on the endometrium?
Increase in number and size of glandular invaginations. The cells secrete watery fluid conducive to sperm (supports travel and provides nutrients)
What effects do the rising titres of oestrogen have on secretion of cervical mucus?
Stimulates secretion of thin and alkaline mucus conducive to sperm transport
What effects do the rising titres of oestrogen have on vaginal epithelium?
Increased mitotic activity
What effects do the rising titres of oestrogen have on metabolism?
Mildly anabolic effects, depresses appetite and maintains bone structure