Repro Phys Flashcards
gonadotropin secretion over the lifetime
- childhood- FSH > LH
- adult- LH > FSH
- senescence- FSH > LH
puberty initiated by?
pulsatile secretion of GnRH
- drives the pulsatile secretion of FSH and LH
- stim secretion of gonadal steroid H’s
melatonin- inhibits what?
GnRH release
- levels are high during childhood and decline in adulthood
- removal of pineal gland precipitates early puberty
seminiferous tubule
- epit formed by sertoli cells, wth interspersed germ cells
- spermatogonia- most immature germ cells
- spermatozoa- mature germ cells
leydig cells
-interstitial cells that lie b/w the tubules
adult testis- consist of?
- 80% seminiferous tubules
- 20% CT interspersed with leydig cells
Sertoli cells- fxn
- provide nutrients to diff sperm
- form TJs
- secrete an aqueous fluid
leydig cells- fxn
-syn and secrete T
testosterone
- syn and secreted by leydig cells
- testds- 17B-hydroxysteroid dehydrogenase- converts androstenedione to T
5alpha-reductase- dowes what
converts T to DHT (active androgen in some tissues)
estrogen in male
- Sertoli cells: T–aromatase–> estradiol
- important role in spermiogenesis
T- in seminiferous tubules and peripheral circulation
- seminiferous tubules- conc by binding to ABP
- peripheral- SHBG and albumin
LH stim what?
- chol –> pregnenolone:
- inc affinity of P450scc enzyme for chol (chol side-chain cleavage enzyme)
- stim syn of P450scc enzyme
tissues producing androgens
- adrenal: chol–> androstenedione
- peripheral tissues: T—5alpha-reductase–> DHT and T–aromatase–> estradiol
- testis- does it all
T- actions during fetal development
- 2nd month- genital organs
- 2-3 month of pregnancy- descent of testes
DHT- actions
- fetal diff of external male genitalia
- male hair distribution and male pattern baldness
- sebaceous gland activity
- growth of prostate
tx for BPH and hair loss in males
-5alpha-reductase inhibitors!!!
caused by DHT
sertoli cells and T
- FSH stim sertoli cells to secrete ABP and inhibin (neg feedback to ant pit)
- aromatization of T to estradiol-17B
spermatogenesis- 3 phases
- mitotic divisions
- meiotic divisions
- spermiogenesis
H factors taht stim spermatogenesis
- LH- stim Leydig cells to secrete T
- FSH- stim sertoli cells to nurse/form sperm
- GH- promotes early div of sperm
- T- growth and div of testicular germinal cells
- estrogens- formed from T by sertoli cells
T def- depends on age of onset
-2-3 mo of gestation- ambiguity in male genitalia
-3rd trimester of pregnancy- cryptorchidism and micropenis
puberty- poor 2 sexual development, eunuchoidism
-post=puberty- dec libido, ED, dec hair growth, low energy, infertility
Kallman’s syndrome
- GnRH neurons fail to migrate into hypothalamus during embryonic development
- delayed/absent puberty, impaired sense of smell
- form of hypogonadotropic hypogonadism
Klinefelter syndrome
(seminiferous tubular dysgenesis)
- men with an extra X chromosome
- at puberty- inc levels of gonadotropins fail to induce normal testicular growth and spermatogenesis
- dec T secretion= primary hypogonadism
male-pattern baldness and BPH
- caused by DHT
- tx- 5alpha-reductase inhibitor
ovarian and endometrial cycle
- ovarian- follicular (coincides w/ prolif phase) and luteal phase (coincides with secretory phase)
- endometrial- menses, prolif, secretory phase
- ovarian- follicular (coincides w/ prolif phase) and luteal phase (coincides with secretory phase)
- endometrial- menses, prolif, secretory phase
- FSH stim a follicle to complete its development
- begins with onset of menses and ends on day of LH surge
- granulosa cells inc prod of estradiol- coincides with prolif phase of endometrial cycle
- rapid rise in ovarian estradiol secretion- triggers surge in LH- causes ovulation!!
luteal phase
- follicle transforms into a corpus luteum
- luteal cells prod progesterone and estrogen
- begins on day of LH surge, ends at onset of next menses
- coincides with secretory phase of endometrial cycle
pulsatile release of GnRH and pulsatile secretion of LH
- GnRH- small rise in LH- early in follicular phase
- later in follicular phase- gonadotrophs in ant pit become more sensitive to GnRH- causes a much larger release of LH
LH and FSH- acto n?
- theca cells- LH R’s
- granulosa cells- LH and FSH Rs
inhibins
- inhibins- prod by granulosa cells- inhibit FSH secretion by gonadotrophs
- FSH stim granulosa cells to produce inhibins
activins
-stim effect of FSH release
positive feedback
- end of follicular phase
- estradiol levels steeply rise at 2nd half of follicular phase
- estradiol levels at a certain threshold for 2 days- HP axis reverses its sensitivity to estrogens- + feedback!
- promotes LH surge!!
- rising levels of progesterone during follicular phase also prod a + feedback
ovary synthesizes?
- estradiol via 17B-HSD
- progesterone
estradiol syn- requires 2 cell types
- theca cells
- granulosa cells
PCOS
- most common cause of infertility in women
- abnormal ovarian steroidogenesis and folliculogenesis
- androgen excess and anovulation
- high androgens- promotes atresia in developing follicles
- elevated LH, low FSH, elevated T
fertilization
- sperm head attaches to zona pellucida- sperm-ZP3 interaction
- acrosomal rxn- inc in Ca inside sperm cells- triggers fusion- exocytosis of the acrosomal contents (hydrolytic enzymes- dissolves the zona pellucida)
- spermatozoon penetrates zona pellucida
- cell membranes of the sperm and oocyte fuse
feritilization- 2
- oocytes 2nd meiotic division and cortical rxn- initiated by inc in Ca- exocytosis of cortical granules (prevents polyspermy- enzymes cause zona pellucida to harden)
- oocyte completes its 2nd meiotic div
- sperm nucleus decondenses and transforms into the male pronucleus
- male and female pronuclei fuse- form the zygote
1st wk of embryogenesis- occurs where
-in lumina of oviduct and uterus
1st wk of embryogenesis
- first 2 cleavages- 2 days
- 16 cell morula- at 3rd day
- blastocyst- days 4-5
- implantation of blastocyst- days 6-7
implantation
- cytotrophoblasts
- syncytiotrophoblasts- adhesive, invasive, endocrine fxnx- secrete HCG- maintains the corpus luteum
decidualization
Maternal response to implantation
- progesterone- endometrial stroma is transformed into enlarged and glycogen-filled decidual cells
- endometrium is called decidua- ready for implantation of embryo
placenta development
-blastocyst implants- syncytiotrophoblast invades the decidua- creates primary chorionic villi (via prolif of cytotrophoblasts)
mature placenta
- chorionic villi- fxnal unit of placenta
- intervillous space
- decidua basalis
placenta- acts as
- fetal gut- supplying nutrients
- fetal lung- exchanges O2 and CO2
- fetal kidney- reg fluid volumes and disposes waste metabolites
- endocrine gland- syn steroids and proteins
birth- occurs when
- 38 wks after fertilization
- 40 wks after last menstrual perioid
fetus decides day of parturition
- placenta produces CRH
- stim fetal prod of ACTH and fetal adrenals to prod cortisol and estrogen
- cortisol- + feedback to inc placental CRH prod
- CRH promotes contractions by sensitizing uterus to prostaglandins and oxytocin
- estrogens also stim contractions
hormonal factors initiating parturition
- estrogen- inc degree of uterine contractility, stim syn of oxytocin Rs
- prostaglandins- initiates labor- uterine stretch stim uterine prostaglandin prod
- oxytocin- causes uterus to contract
- relaxin
lactation initiation
- PRL inc
- high estrogen and progesterone inhibit onset of lactogenesis- fall following birth
- suckling- inhibits hypothalamic dopaminergic neurons
- PRL inc
- high estrogen and progesterone inhibit onset of lactogenesis- fall following birth
- suckling- inhibits hypothalamic dopaminergic neurons
suckling
- feedback to hypothalamus to dec dopamine release- removes inhibition- inc in PRL
- oxytocin also released- contraction of myoepit basket cells producing milk ejection
4 effects of suckling on H release
- suckling stimuli- act afferent neural pathway to spinal cord and then hypothalamus
- dopamine release is inhibited- PRL released!
- prod and release of oxytocin from post pit
- arcuate and preoptic area of hypothalamus inhibited- causes a fall in GnRH- dec LH and FH- inhibits ovarian cycle
