Physio Flashcards
during childhood LH or FSH is higher?
reproductive period?
senescence?
- FSH
- LH
- FSH
what is one of the earliest events of puberty
appearance of large nocturnal pulses of LH during REM sleep
what is the characteristic feature of the GnRH that drives puberty
pulsatile . . so long acting GnRH analogue administration will not initiate pubery
what is a natural inhibitor of GnRH release that is secreted by the pineal gland
melatonin
Removal of pineal gland precipitates what
early puberty
describe the distribution of tissue in an adult testis
- 80% seminiferous tubules
- 20% connective tissue interdispersed with Leydig cells
What is the function of a Sertoli cell
- provide nutrients to differentiating sperm
- form tight junctions with each other, creating a barrier between testes and bloodstream
- secrete an aqueous fluid into the lumen of the seminiferous tubules that helps to transport them through the tubules into the epididymis
What is the function of Leydig cells
-Synthesis and secretion of testosterone
what enzymes to testes lack to ensure that no glucocorticoids or mineralocorticoids are synthesized
21 and 11 beta hydroxylase
What enzyme do testes have and what does it do
- 17-beta- hydroxysteroid dehydrogenase
- converts androsternedione to testosterone
In the lumen of seminiferous tubules, Testosterone is concentrated by binding to what?
Androgen binding protein (ABP)
what in peripheral tissue converts testosterone to dihydrotestosterone
5-alpha-reductase
Most of circulating testosterone is bound to what protein along with albumin
-Sex hormone binding globulin (SHBG)
what cells in testes produce small amount of estrogen?
they contain what that makes this happen?
- Sertoli cells
- aromatase mediates T–>estradiol
What stimulates the conversion of cholesterol to pregnenolone and regulates the overall rate of testosterone synthesis by the Leydig cell
LH
- by increasing affinity of P450cc (cholesterol desmolase) for cholesterol
- also stimulates synthesis of this enzyme . . long term action
lack of descent of testes is called what
cryptorchidism
what can be used to treat benign prostatic hypertrophy and hair loss in males
5-alpha reductase inhibitors
describe receptor and pathway in Leydig cells
- LH receptor
- cAMP-PKA pathway
What stimulates Sertoli cells
testosterone and FSH
What do Sertoli cells produce
- proteins synthesis
- inhibin
- ABP
- Aromatase
what does inhibin from Seroli cells do
inhibits FSH release
what hormone besides LH and FSH is involved in division of sperm
FH
FSH stimulates what immature sperm cell?
LH?
- primary spermatocyte —> meiosis 1
- Secondary spermatocyte –> Meiosis 2
effects of T deficiency in 2nd to 3rd month of gestations
-varying degrees of ambiguity in male genitalia and male pseudohermaphrodism
effects of T deficiency in 3rd trimester of pregnancy
-cryptorchidism and micropenis
effects of T deficiency in puberty
- poor secondary sexual development and overall eunuchoid features
- persistence of prepubertal characteristics and often by the presence of characteristics typical of the opposite sex
effects of T deficiency in post puberty
- decreased libido
- erectile dysfunction
- decreased facial and body hair growth
- low energy
- infertility
Genetic disorder that occurs when GnRH neurons fail to migrate into the hypothalamus during embryonic development
Kallman’s syndrome
what is Kallman’s syndroeem characterized by
- delayed or absent puberty and an impaired sense off smell
- form of hypogonadotropic hypogonadism
- form of secondary hypogonadism
describe Klinefelter syndrome
- seminiferous tubular dysgenesis: men with extra X chromosome
- Affected persons are phenotypically male because of the presence of Y chromosome . . appear normal at birth
- at puberty, increased levels of gonadotropins fail to induce normal testicular growth and spermatogenesis
- Androgen production is usually low, levels of gonadotropins are elevated thereby indicating primary hypogonadism
- seminiferous tubules are largely destroyed, resulting in infertility
male pattern baldness and benign prostatic hypertrophy are caused by what
DHT
what are the 2 phases of the ovarian cycle and what endometrial cycle phases do they coincide with
- follicular (proliferative phase)
- Luteal phase (secretory phase)
Describe the follicular phase of the ovarian cycle
- FSH stimulates a follicle to complete its development
- begins with onset of menses and end on day of LH surge (day 14)
- Granulosa cells of the follicles increase production of estradiol, which stimulates the endometrium to undergo rapid and continuous growth and maturation
- coincides with proliferative phase of endometrial cycle: rapid rise in ovarian estradiol secretion eventually triggers a surge in LH, which causes ovulation
Describe the luteal phase of the ovarian cycle
- follicle transforms into a corpus luteum
- Luteal cells produce progesterone and estrogen which stimulate further endometrial growth and development
- Begins on day of LH surge and ends at onset of next menses
- coincides with secretory phase of endometrial cycle
Which ovarian cells produce activins and inhibins
Granulosa cells
which ovarian cells produce progestins
both Theca and Granulosa cells
Which ovarian cells produce androgens
Theca cells
What causes the gonadotrophs of the anterior pituitary to be much more sensitive to GnRH in the LATE follicular phase
high levels of estradiol
what receptors do theca cells have?
granulosa cells?
- LH
- both LH and FSH
What is the difference in structure between activins and inhibins produced by granulosa cells
- Inhibins: one alpha and one beta subunit
- activins: two beta subunits
what levels increase during the luteal phase
- progesterone (highest)
- estradiol
- inhibin
what happens during the late luteal phase
-the gradual demise of the corpus luteum leads to decreases in the levels of progesterone, estradiol, and inhibin
what cells of the ovary produce progesterone?
both . . then from granulosa cell it diffuses to theca cell
what does a granulosa cell lack so that it can’t convert progesterone to androstenedione
17-alpha-hydroxylase and 17,20 desmolase
-androstenedione from theca cells diffuses over to granulosa cells
when does temperature rise in the menstrual cycle
after ovulation
the secretory phase of the endometrial cycle is stimulated by what
progesterone
during late secretory phase, progesterone promotes the differentiation of the stromal cells to what?
predecidual cells which must be prepared to form the decidua of pregnancy
most common cause of infertility in women
PCOS
clinical manifestation of PCOS
androgen excess and anovulation
-presentation: young, obese, hirsute females of reproductive age; oligomenorrhea or secondary amenorrhea; infertility
relevant lab values for PCOS
- elevated LH
- low FSH
- elevated testosterone
what protein attaches sperm to zona pellucida that surrounds the oocyte
ZP3
describe the acrosomal reaction of fertilization
-increase in Ca inside sperm cell triggers fusion of the outer acrosomal membrane with the sperm cell’s plasma membrane and resule in exocytosis of most acrosomal contents
in the steps of fertilization, what happens after the membrane of the sperm fuses with the membrane of the oocyte and the sperms contents go into the egg (cortical reaction)
- increase in Ca in oocyte
- massive exocytosis of cortical granules
- release of enzyme that act on glycoproteins in the zona pellucida and cause them to harden
- prevents polyspermy
what form of a ferilized egg implants
blastocyst
what cells express adhesive surface proteins (cadherins and integrins) that bind to uterine surface epithelia, as the embryo implants, these bind to components of the uterine extracellular matrix
syncytiotrophoblasts
What cells secrete on LH like protein called human chroionic gonadotropin (hCG) at the onset of implantation which maintains the viability of the corpus luteum of pregnancy
syncytiotrophoblasts
what umbilical vessel is oxygen rich?
poor?
- vein
- artery
what hormones does the placenta produce and what does each do?
- hCG: helps initiate pregnancy and maintain for first 10 weeks
- Progesterone: maintains pregnancy after 10 weeks and keeps endometrium quiescent
- hPL: contributes to diabetogenic effects of pregnancy. increases blood sugar levels by antagonizing insulin
- estrogens: promote contraction of uterus
Describe the signals from the placenta and fetus that initiate labor . . . Parturition
- Placenta produces CRH
- Rapid release causes rise in cirulating levels
- stimulates fetal production of ACTH and fetal adrenals to produce cortisol and fetoplacental estrogen production
- cortisol feeds back to increase placental CRH production (positive feedback)
- CRH promotes contractions by sensitizing uterus to prostaglandins and oxytocin
- estrogens also stimulate contractions
what hormone is believed to initiate labor
prostaglandins
Describe the role of oxytocin
- causes the uterus to contract immediately after the fetus is expelled, limiting blood flow and blood loss
- increases uterine synthesis of prostaglandins
- However, increased oxytocin secretion does NOT initiate thee rhythmic uterine contractions characteristic of the onset of labor
describe the role of relaxin
- protein produced by the corpus luteum, placenta
- keeps uterus quiescent during pregnancy
- soften and dilates cervix during labor
What is the effect of estrogen and progesterone on lactation
- both inhibit onset of lactogenesis
- they abruptly fall following parturition
what does suckling do for lactation
- inhibits hypothalamic dopaminergic neurons
- primary neural stimulus post parturition
what is the role of oxytocin in lactation
it is galactokinetic and causes contraction of the myoepithelial basket cells producing milk ejection (“let-down”)
