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83 Cards in this Set
- Front
- Back
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What are the primary reproductive organs?
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Gonads
Testes (males) Ovaries (females) |
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What are the accessory reproductive organs?
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Systems of ducts through which sperm or eggs are transported and glands that empty into them
Breasts are also included in this category for females |
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What are the functions of the gonads?
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1) Gametogenesis: production of reproductive cells (gametes): spermatozoa and ova
2) Secretion of sex hormones (specific steroids): testosterone (androgen) and estrogen and progesterone in females |
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Is the difference in reproductive endocrinolog between males and females quantitative or qualitative?
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Quantitative
Androgens aren't unique to males and estrogen isn't unique to females |
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What makes estrogen in males?
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Testes make a small amount of estrogen
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What produces androgens in females?
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Androgens produced in small amounts in ovaries and in larger amount by the adrenals
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Canadrogens be converted to estrogens?
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Yes
Takes a single enzymatic step in non gonadal tissues (i.e. bone) |
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What is th function of strogen in males?
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Bone growth and density
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What is the sequence for control of reproductive function? (similar for males and females)
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1) GnRH (gonadotropin releasing H) secreted by the hypothalamus travels to anterior pituitary via hypothalmo-pituitary portal vessels
2) Stimulates release of pituitary gonadotropins: FSH and LH 3) FSH and LH stimulate development of spermatozoa or ova and secretion of sx steroids 4)Sex steroids exert their effects in gonads, other parts of the reproductive system and the body |
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What does inhibin do?
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Ptn hormone produced by gonads
Feeds back on anterior pituitary |
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What is the main function of the testes?
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Produce mature germ cells (spermatogenesis) and steroid H (steroidgenesis)
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What's the difference between male and female precursor germ cells?
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Male continually renews his supply of precursor germ cells, whereas a female is born with her life's supply of ova
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What are spermatogonia?
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Precursor male germ cells
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Whre does spermatogenesis take place?
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Seminiferous tubules of the testes
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How long does it take for immature spermatogonia to mature to spermatozoon?
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~60 days
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What 2 cells types are critical for the maturation of spermatozoa?
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1) Leydig cells: located outside of the seminiferous tubules
2) Sertoli cells: located within the seminiferous tubules. Responsive to FSH. Envelop the germ cells throughtout sperm maturation |
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What do Leydig cells respond to? How?
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Respond to LH
Synthesize androgens |
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What do Sertoli cells respond to? How?
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FSH
Synthesize Androgen Binding Protein (ABP) and inhibin |
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What does spermatogenesis depend on?
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Androgen concentration within seminiferous tubules (~10x higher than [androgen] in circulation, or spermatogenesis ceases)
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What is required to ensure that there is a high androgen concentration in the seminiferous tubules?
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ABP (androgen binding protein) made by Sertoli cells
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What kind of signalling is involved in spermatoenesis?
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Paracrine signalling
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What 2 negative feedback mechanisms regulate testicular androgen synthesis?
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1) Hypothalamic-pituitary-leydig cell axis: GnRH stimulates release of LH and FSH -> stimulate leydig cells and sertoli cells.
Leydig cells make androgen, which inhibit the release of GnRH, LH and FSH 2)Hypothalamic-pituitary-seminiferous-tubules axis: non-steroidal inhibin secreted by the sertoli cells inhibits FSH release only |
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What's the difference between feedback control in males and females?
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Males fon't have + fdbck control
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What are the principle functions of the ovaries?
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-Produce mature eggs
-Produce steroid hormones that regulate the reproductive tract and influence sexual behaviour |
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What do the ovaries contain at birth?
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Oocytes: Non-proliferating germ cells
Start with about 2 million, the entire supply of ova for life ->400,000 ova left at puberty |
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What are the fundamental preproductive units of the ovary?
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Granulosa cells: single layer that surrounds the oocytes
Primordial follicles: made up of a basement mb |
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what happens once primordial follicles grow into primary follicles?
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Gonadotropins and steroid hormones control growth until th follicles ovulate or degenerate (atresia)
This event is independent of the pituitary |
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What happens in follicular growth?
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Develop oocytes suitable for ovulation
Develop new endocrin organs |
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What are the stages of follicular growth?(4)
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1) Enlargement and differentiation of oocyte, which grows and becomes Zona Pellucida (acellular layer rich in glycoptns surrounding the oocyte)
2) Granulosa cells divide and increase to 2+ layers -> Primary follicles (this is influenced by FSH and estrogens, which are important for LH receptor expression on granulosa cell surface) 3) LH and FSH help primary follicle--> secondary follicle, which has receptors for FSH, LH and estrogen. Follicular antrum,has secretions from granulosa cells, appears 4) Due to FSH and LH, granulosa cells make follicular fluid, which takes up a large part of the preovulatory follicle |
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What happens as the follicle goes from 1ry to 2ry?
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Cells from ovarian stroma surrounding the follicle differentiate and become steroid producing cells (Theca cells)
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Whatdo the Theca interna and granulosa cell synthesis?
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Higher amounts of estrogen
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What can follicular devlopment lead to?
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1) Follicular atresia
2) Ovulation |
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What is follicular atresia?
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Form of degeneration
Only one follicule will ovulate/month other secondary follicles will degenerate |
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What is ovulation?
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Follicular rpture
->might be due to increase in intrafollicular P and proteolysis of ovarian wall of mature graafian follicle |
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What follows ovulation?
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Luteinization
->Ruptured follicle becomes Corpus luteum:temporary endocrine organ |
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What does the corpus luteum secrete?
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Progesterone
(also makes estrogen) |
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What contributes to the formation of the corpus luteum?
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Granulosa cells
Theca |
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What happens if there is no fertilization of the ovum?
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Drop off in level of progesterone and estrogen
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What happens if implantation ocurs?
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Corpus luteum becomes the corpus luteum of pregnancy
-> Responible for synthesis of progesterone (P) and estrogen (E) -> create proper endocrine env't for maintenance of pregnancy (till placenta can make P and E) |
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What is luteolysis?
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Happens in absence of implantation
Luteal regression induced by prostaglandins: decrease LH binding and steroidgenesis |
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What happens before the 1st day of the mentrual cycle?
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Endometrium proliferates and becomes thick under estradiol influence
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What happens on day 1 of the menstrual cycle?
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Detection of vaginal bleeding
Deterioration of utrine endometrium |
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When does mensis begin?
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When estradiol and P are low in circulation, when blood vessels upplying the endometrium constrict, reducing the blood supply
->endometrium deteriorates, flows through cervix and vagina |
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What happens during menses?
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Bleeding for 5 days
Ovaries ~ endocrinologically inactive |
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What do low levels of estradiol and P lead to?
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FSH secretion by pituitary
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What happens in moderate levels of estradiol?
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FSH release is blocked
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What are inhibins? What do they do?
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Non-steroid H
Selectively inhibit secretion of FSH ->decrease in inhibins may contribute to ~5 day rise in FSH |
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What happens under FSH influence?
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Develop cohort of ovarian follicles
Stimulates granulosa cells of follicles to proliferate --> produce E, which stimulates granulosa cell dev'l |
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What happens on day 8?
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One follicle becomes dominant and committed to further dev'l
Remaining follicles degenerate through atresia |
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What does the dominant ollcl produce?
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Increasing levels of estradiol
-> causes uterine endometrium proliferation |
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What happens by day 13?
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Endometrium is very thick
Estradiol influence induces P receptors in the endometrium |
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What is the effect of moderate amount of estradiol on the brain?
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-Neg fdbk on FSH release
-Stimulate synthesis of LH by pituitary and increase sensitivity of pituitary to GnRH -> stimulates LH synthesis **estradiol stimulates LH synthesis, NOT release, .: LH accumlates to high levels wihin the pituitary |
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What is the effect of high amount of estradiol on the brain?
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[Estrogen] continues to increase under dev'l of follicle
Inc [estrogen] stimulates LH release--> LH surge day 14: small inc in FSH release Estrogen positive fdbk control mech: estradiol stimulates LH synthesis and anterior pituitary gets inc sensitivity to GnRH .: increased synthesis of LH by anterior pituitary |
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What kind of fdbks does estrogen exert?
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Negative: decreased GnRH and LH release
Positive: Increased sensitivity of anterior pituitary cells to GnRH and increased LH synthesis |
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What happens during the sudden LH surge?
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Follicle now very big
Follicle rupture and ovum is ejected |
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What do oral contraceptives do?
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Pills that have E and P
Maintain moderate circulating levels of E and P -> suppress release of LH and FSH from pituitary and prevent ovarian follicles from maturing and being ovulated |
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What H influence corpus luteum? How?
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LH: follicle -> corpus luteum, make a lot of E and P, induce endometrial growth of the uterus
Progeterone: endometrium becomes glandular |
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What happens in the luteal phase?
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14 days
Corpus luteum produces steroids that dominate If no implantation after 14 days, corpus luteum degenerates, steroid levels drop, uterine edometrium degenerates, menstruation begins and pituitary starts to increase its secretion of FSH |
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What's the dif btw menstrual and estrous cycles?
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Menstrual cycles only in primates
Estrous cycles: no bleeding Relative H changes in both cycles are similar |
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What happens at ovulation?
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Unfertilized egg taken to the fimbria of the oviduct (fallopian tube) and it propelled to the lumen of the uterus
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What happen to egg if fertilized by spermatozoa?
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Eggs starts dividing o the blastocyst stage as it is transported down the oviduc into the uterine lumen
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What prepares the endometrium for blastocyst implantation?
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Estradiol and P
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Wht does theblastocyst differentiate into?
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-Trophoblast: will become the placenta
-Inner cell mass: will form the embryo |
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What does the throphoblast do?
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Invades uterine mucosa, embedding of developing embryo in endometirum
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What does the throphoblast synthesize at implantation?
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HCG: has LH-like properties, stimulates corpus luteum to keep secreting gonadal steroids
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When does the placenta take over endocrine function of the corpus luteum?
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After 12th week of pregnancy
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a is the fetoplacental unit?
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Placenta + developing fetus
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What are important in the synthesis of estriol (type of E)?
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Functional interdependence between the fetal and maternal compartments and fetal liver
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When do HCG levels peak?
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8-9 weeks after fertilization
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What is lactation?
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Secretion of milk by the breasts (mammary glands)
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What happens to mature non-pregnant mammary glands (ductal)?
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Duct growth and branching, little dev'l of alveoli at onset of puberty under action on inc levels of E
-P stimulates alveoli growth -breast enlargement due to fat deposition -Corticoid and GH also contribut to growth of mature non-pregnant mammary gland |
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What do E and P do?
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E: causes proliferation
P causes specializaion |
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What happens in the pregnant mammary gland (lobulo-alveolar)?
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Ductal and alveolar structures fully develop during pregnancy under influence of E, P, prolactin, human placental lactogen, GH, cortisol, thyroxin)
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What controls milk production during pregnancy?
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Prolactin
->High levels of E inhibit milk secretion |
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What happens to levels of E and prolactin after parturition (birth)?
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Levels of E decrease
Prolactin levels remain high |
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What doesoxytocin do?
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Ducts contract causing milk ejection (fdbk to produce more milk)
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What releases prolactin and oxytocin?
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Prolactin: from anterior pituitary
Oxytocin: from posterior pituitary These releases stimulated by afferent fibers from the nipple ->Prolactin sustains milk production ->Oxytocin causes milk ejection |
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What does milk contain?
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Water
Protein Fat Carbohydrate lactose Antibodies ->can transmit viruses and drugs through nursing |
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What is lactational amenorrhea?
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Natural contraception
-> Maintained nursing inhibits secretion of FSH and LH, blocks resumption of reproductive cycle (but need frequent suckling or pregnancy can occur) |
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What is menopause?
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End of reproductive period
Most ovarian follicles have disappeared by atresia and a few hundred have been ovulated during menstrual cycle |
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What happens in menopause?
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Depletion of follicles result in loss of capacity for steroid (E and P) hormone production by the ovary
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What effects does lack of E have?
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Hot flashes
dry vagina restlessness Bone loss (osteoporosis-> long term) |
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What happens when ovarian steroid hormone production ceases?
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Eliminate negative fdbk loop and rise in lvls of plasma gonadotropin FSH and LH
->cst high lvls of FSH= sign of menopause |
