A & P 2 - Menstrual Cycle

Front 1

What are the hormonal regulations in the Menstrual cycle?

Back 1

GnRH:
-secreted by hypothalamus controls ovarian and uterine cycle
-stimulates release of FSH and LH from anterior pituitary

FSH:
-stimulates ovarian follicles to secrete estrogens

LH:
-triggers ovulation
-stimulates thecal cells to produce androgens to be converted into estrogens
-promotes formation of corpus luteum - produces estrogen, progesterone, relaxin, and inhibin

Estrogen:
-inhibits release of GnRH, LH, and FSH
-increase protein anabolism and lowers blood cholesterol

Progesterone;
-secreted mainly by corpus luteum
-prepares endometrium for implantation and mammary glands for milk production
-inhibits GnRH and LH

Relaxin:
-relaxes uterus by inhibiting contraction of myometrium

Inhibin:
-inhibits FSH and LH

Front 2

What happens in the Ovarian cycle?

Back 2

duration:
-28 days
-follicular from 9-23 days
-ovulation from 1-3 days
-luteal phase is more constant at 14 days

Follicular phase:
Preantral follicular growth:
-formation of primary and secondary follicle
Antral Follicular Growth
Preovulatory stage:
-formation of graafian or mature follicle (preovulatory)
Selection of dominant follicle:
-by day 5-7 dominant one outgrows the rest
-remaining undergo atresia due to decreased FSH by increase inhibin and estrogen secretion by dominant follicle

Luteal Phase:
-corpus luteum is formed which is a temporary endocrine organ
Corpus luteum:
-life span is 12 days
-7-8 days after ovulation reaches maximum size
-degenerates at 26th of menstrual cycle in absence of fertilization
-if conception has occurred, maintained by hCG

Front 3

What are the phases of the Menstrual Cycle?

Back 3

Menstrual phase:
-first 5 days, day 1 = beg. of new cycle
events in ovaries:
-increase FSH --> primordial follicles --> primary --> secondary follicles
events in uterus:
-low estrogen and progesterone --> release of prostaglandins --> unterine spiral arteriole constriction --> menstrual discharge
-shedding of functional layer of endometrium, only stratum basalis remains (bottom 1/3)

Preovulatory stage:
-days 6-13 out of 28
events in ovaries:
-secondary follicles secrete estrogen and inhibin
-estrogen and inhibin of dominant follicle decrease FSH causing other follicles to stop growing
-fraternal twins develop from 2-3 secondary follicles becoming codominant
events in uterus:
-estrogens stimulate repair of endometrium
-stratum basale undergoes mitosis to form new stratum functionalis
-preovulatory = proliferative due to endometrium proliferation

Ovulation:
-day 14: rupture of graafian folicle and release of secondary oocyte
-LH surge brings about ovulation

Postovulatory phase:
-15-28
events in one ovary:
-mature follicle collapses to form corpus luteum under influence of LH
-secretes progesterone, estrogen, relaxin, and inhibin
-IN OVARIAN CYCLE THIS IS LUTEAL PHASE
events in uterus:
-progesterone and estrogen promote growth of endometrium
-SECRETORY PHASE OF UTERINE CYCLE
-if no fertilization, lower estrogen and progesterone causing menstruation

Front 4

What happens in the Corpus Luteum?

Back 4

If oocyte not fertilized, corpus luteum lasts 2 weeks:
-degenerates in corpus albicans
-lower progesterone, estrogen, inhibin --> increase GnRH, FSH, LH due to loss of negative feedback

If oocyte fertilized, corpus luteum lasts more than 2 weeks:
-hCG produced by chorion stimulates corpus luteum

Front 5

What happens in Menopause?

Back 5

cessation of ovarian activity and menstruation

mechanism:
-low plasma estrogen and progesterone
-increase FSH and LH

Signs:
-urogenital atrophy
-hot flashes

Front 6

What are some birth control methods?

Back 6

Sterilization:
Female - tubal ligation:
-fallopian tubes cute, prevent eggs from reaching sperm
Male - vasectomy:
-ligation of vas deferens

Spermicides:
-chemicals kill sperm
-different forms - jelly, film, foam, suppository

Intrauterine devices:
-object placed in uterus to prevent pregnancy
-copper containing device that releases progestogen

Hormonal methods:
-birth control pills, 99 % effective
mechanism:
-stop ovulation
-thins uterine lining
-thickens cervical mucus

Front 7

What are some Hormonal contraceptions?

Back 7

oral - birth control pill
injections - depo-provera
-implants - norplant I and II

Combinatino of synthetic estrogens and progestogens or progestins:
-estrogen inhibits FSH and LH --> suppression of growth and development of ovarian follicles
-progesterone prevents ovulation
-increase thickness of cervical mucus --> decrease sperm motility
-inhibition of endometrial proliferation

Progestogen-only pills:
-hostile cervical mucus --> decrease motility and secretion of fallopian tubes --> prevention of fertilization
-prevention of fertilized ovum from implantation

Postcoital contraception (morning after pill):
-high dose estrogens and prostaglandins
-increase uterine contractions --> interferes with transport and implantation of the conceptus
ex. Ella

Front 8

What happens in Abortion?

Back 8

premature expulsion of products of conception from uterus

induced:
-mifepristone is an antiprogestin, blcoks action of progesterone by bind and blocking progesterone receptors