Menstruation Flashcards
Background
Begins usually at 12 yrs. Continues till around 50.
Factors that affect it:
- Race
- Body weight
- Medical conditions
- Family history
Cycles relies on HPG axis.
Stages of menstruation
3 Phases: Follicular, Ovulatory, Luteal.
Menstruation =- 3-6 days. Superficial layer of endometrium is shed. Flow of blood, mucus, tissue starts.
Follicular = Endometrium regenerates after flow stops. GnRH secreted from hypothalamus and causes anterior pituitary to release FSH and LH. They act on ovaries and promote development of small follicles groups each with a ovum (egg). One develops faster making Graafian follicle (GF), which secretes oestrogen. Other ova degenerate.
Oestrogen does:
- endometrial thickening
- thinning of the cervical mucus to allow easier passage of sperm
- inhibition of FSH production and stimulates LH by the pituitary gland
Ovulatory = Oestrogen causes endometrium to regenerate day5/6 to mid cycle. Endometrium thickness and vascularity increases. When oestrogen levels peak prolific cervical secretion of mucus is released (rich in protein and Carbs helps sperm enter ovum). High endogenous oestrogen b4 mid cycle sensitizes the LH-releasing cells of the anterior pituitary to the action of GnRH, = mid-cycle surge in LH secretion (approx. day 12). CAUSES rapid swelling and rupture of GF = ovulation.
IF fertilised. Ovum passes down fallopian tube in to uterus
Luteal =Ruptured GF proliferates and becomes corpus luteum which secrets progesterone. Progesterone acts on endometrium making it suitable for implantation for fertilised ovum and makes cervical mucus thicker stopping sperm. Progesterone also sends negative feedback to Hypothalamus and pituitary decreases synthesis and release of FSH and LH.
Fertilization dont happen progesterone secretion stop at end of cycle triggering menstruation.
IF it occur Corpus luteum continues to secrete progesterone.
Progesterone does:
- endometrium becoming receptive to implantation of the blastocyst (divding egg cluster made by fertilised egg)
- negative feedback causing decreased LH and FSH (both needed to maintain the corpus luteum)
- increase in the woman’s basal body temperature
