Female Reproduction Flashcards
1
Q
Ovarian cycle
A
-a series of hormone-mediated changes in the ovaries culminating in the monthly production of a viable ovum in women of reproductive age
2
Q
Follicular phase
A
-FSH stimulates development of follicles
3
Q
Stages of ooctye maturation
A
- growth and maturation of a primordial follicle during the follicular phase (FSH and rising estradiol)
- rupture of a mature Graafian follicle and oocyte discharge during the ovulatory phase at mid-cycle (LH surge)
- and conversion of the ruptured follicle to a corpus luteum during the luteal phase (LH, high progesterone plus some estradiol)
- degeneration of the corpus luteum to form a corpus albicans proceeds if fertilization does not occur (low estrogen and progesterone)
4
Q
Ovulatory phase
A
-LH surge causes rupture of the Graafian follicle
5
Q
Luteal phase
A
-LH converts the ruptured follicle to a corpus luteum
6
Q
Ovary, Ova and Follicles
A
- until puberty, the ovary contains numerous primordial follicles that remain in the dorman state
- after puberty, several follicles begin ripening with each menstrual cycle
- only one follicle becomes a mature follicle; the others ultimately regress
- after ovulation and release of the ovum, the mature follicle involutes to form the corpus luteum, which persists to the end of the cycle
7
Q
Maturation of ovarian follicle
A
- primordial follicles are 30-60 um in diameter, and their production from primary oocytes is complete by 6 months of age
- the primary follicles develop as shown during the monthly ovarian cycle
- the graafian follicle attains a diameter of 20-33 mm
8
Q
Estradiol (follicular phase)
A
-promotes proliferation of the endometrium and primes the uterus for progesterone actions by increasing the number of receptors
9
Q
Progesterone (luteal phase)
A
-converts the proliferative uterus to a secretory uterus
10
Q
Proliferative phase
A
- endometrium thickness increases from 1-2 mm to 8-10 mm
- dominated by estrogens and is variable in length (ave 14 days)
11
Q
Secretory phase
A
- dominated by progesterone and has a fixed length of 14 days following ovulation.
- progesterone promotes accumulation of glycogen, increased glandular secretions, and increased vascularity
12
Q
Menstrual phase
A
- associated with prostaglandin-mediated vasoconstriction of spiral arteries and local ischemic injury/inflammation
- regression of the corpus luteum
13
Q
Hypothalamic pituitary ovarian axis neg/pos feedback
A
- GnRH stimulates release of LH and FSH by the pituitary
- estrogen synthesized by developing ovarian follicles has negative feedback effects on the axis in the luteal phase
- in the late follicular phase- blood estradiol reaches a high level that initiates positive feedback and a surge in LH and FSH
- estradiol, progesterone and inhibin produced by corpus luteum have negative feedback
14
Q
Secretion of LH
A
-high circulating esterogens during the late follicular phase “sensitize” the anterior pituitary gonadotrophs to stimulation by GnRH thereby producing the mid-cycle surge in LH and (FSH) release that is necessary for rupture of the growing follicule and ovulation
15
Q
Hypothalamic-pituitary ovarian axis
A
- small bodies neurons in the arcuate nuclus secrete GnRH (decapeptide)
- reaches gonadotrophs in the anterior pituitary via the long portal veins, to increase secretion and synthesis of FSH (during the follicular phase) and LH (during luteal phase)
- FSH binds receptors on granulosa cells, stimulating gene transcription and synthesis of relevant enzymes (aromatase), activins, and inhibins
- LH binds to receptors on ovarian theca cells stimulating the biosynthesis of progestins and androgens
- androgens enter granulosa cells where converted to estrogens
- activins and inhibins only act on anterior pituitary
- estrogens and progestins act on anterior pituitary and hypothalamic neurons both positive and neg feedback
16
Q
Gonadotropin secretion
A
- GnRH binds G protein coupled receptor on the gonadotroph membrane triggering Ip3/DAG signaling pathway
- synthesis and release of FSH and LH- heterodimers with alpha and beta subunits
- need calcium to for exocytosis
17
Q
Estrogen is derived from what?
A
- cholesterol- estradiol and progesterone are primary forms of steroid hormones synthesized
- in serum they bind loosely to albumin and sex hormone binding globuins
- they exert effects on many tissues in the body including the breast, bone, vagina, cervix, fallopian tubes and uterus
- estrogens are inactivated in the liver through conjugation with glucuronic or sulfuric acids and excreted in the urine
18
Q
What is two cell-two gonadotropin model
A
- during follicular phase major product is estradoil; in luteal phase, the major products of the corpus luteum are the progestins
- in follicular phase, LH primes theca cell to convert cholesterol to androstenedione
- theca cell lacks aromatase, it cannot generate estradoil from this androstenedione
- androstenedione diffuses to the granulosa cell whose aromatase activity has been stimulated by FSH
- in the luteal phase, the vascularization of the corpus luteum makes LDL availible to granulosa lutein cells
- both theca lutein and granulosa lutein cells can produce progesterone
- for production of 17 alpha hydroxyprogesterone has to go to theca lutein cell which has the enzyme for it the granulosa cell doesnt
- theca cell can also produce androstendeione that can then move to granulosa to be made into estradiol
19
Q
Estrogens and DNA
A
- during the follicular phase estrogens induce endometrial gene products that promote growth; it also induces progesterone receptors, thus priming the uterus for progesterone actions in the luteal phases
- during the luteal phase, progesterone induces genes that convert the uterus to a secretory type (enhancing differentiation of epithelail and stromal cells, promoting glycogen storage and secretion of carbohydrate-rich mucus
20
Q
Estrogen effects
A
- proliferation of uterine endometrial stroma and development of endometrial glands
- proliferation and development of mucosal lining of the fallopian tubes
- stimulation of bone growth by inhibition of osteoclastic activity, promoting rapid growth, followed by uniting of epiphysis with shafts of long bones to stop growth
- increased fat deposition in subcutaneous tissues
- promote deposition of fat, development of stromal tissue and ductile growth in breasts
- promote deposition of fat in subcutaneous tissue
21
Q
Progesterone effects
A
- secretory changes in uterine endometrium (of major importance)
- decreased frequency and intensity of uterine contractions
- increased fallopian tube secretions
- promotes development of lobules and alveoli in breasts
22
Q
Menstrual Cycle
A
- during the female menstual cycle, changes take place in the ovaries and uterus
- during follicular phase, several primary follicles undergo further development in response to FSH and synthesize androgens, which are converted to estradiol under the influence of LH
- ultimately, one follicle fully matures and others regress
- the uterine endometrium proliferates in response to estradiol
- near midcycle, estradiol rises to a level that initiates positive feedback, and thus a surge in LH and FSH release by the anterior pituitary which results in ovulation
- during the ensuing luteal phase, the mature follicle becomes the corpus luteum, which secretes progesterone and estradiol
- the uterus undergoes further proliferative and secretory changes
- unless pregnancy occurs, endometrial sloughing and menstruation eventually occur, marking the beginning of a new cycle
23
Q
Puberty
A
-the transition to cyclic female reproductive function
24
Q
Thelarche
A
-breast development
25
Adrenarche
-increased secretion of adrenal androgens
26
Menarche
-menstrual cycles begin
27
Inhibition of sex steroids before puberty
- hypothalamic-pituitary-gonadal axis becomes functional during puberty
- release GnRH then FSH/LH
- however the link that activates the hypothalamus appears to be immature until puberty, when pulsatile secretion of GnRH is observed first at night and then during the day as well as night
28
Gonadotropin function throughout life
- child- even very low estrogen levels are sufficient to fully suppress gonadotropin output
- adolescence- higher levels of estrogens are required
- adult- estrogens must be at very high levels to suppress gonadotropin release
29
Menopause overview
- cyclic reproductive function and menstruation cease
- average age is 51-52 years
- virtually no remaining ovarian follicles
- levels of circulating sex steroids decrease
- levels of circulating gonadotropins rise
- a variety of physical and mental changes occur
- changes in vaginal pH
- sleep disturbances
- night sweats, hot flashes
- cardiovascular disease, osteoporosis, Alzheimers
30
Number of follicular cells
- 6-7 million germ cells in the two ovaries in the 20 week female fetus
- at birth 1-2 million
- puberty 400,000
- about 400 oocytes are ovulated during reproductive life
- menopausal women have few or no remaining follicles to mature and produce estrogens and progestins
- there is atresia of cells throughout the reproductive lifetime, thereby accounting for most of the loss of follciles
- reduced estrogen production leads to increased gonadotropin production in menopausal women
31
Gonadotropins and menopause
- the amounts of circulating gonadotropins increase dramatically after menopause (10-20 fold) due to the loss of negative feedback on the pituitary and hypothalamus by estrogens and progestogens
- the increase in LH and FSH is due to increased production, not a change in clearance
- immunoassay of FSH and LH is often used to determine if a woman has gone through monopause
32
Estrone
- production by muscle and adipose tissue,derived primarily from androstenedione in the adrenal gland ( and ovary) , provides a postmenopausal sources of estrogen
- 15-25% as potent
- functionality of this system accounts for some women having different menopausal symptoms
33
Effects of menopause
- estrogens prevent bone resorption/loss
- decreased circulating estrogens after menopause places many women at increased risk for osteoporosis and fractures
- compression fractures in the vertebrae lead to loss of height, spinal deformitiy (thoracic kyphosis aka dowager's hump) and back pain
- a healthy diet plus supplemental calcium and vitamin D, and weight bearing exercise are recommended to preserved bone mass
