Male reproductive physiology- Lopez Flashcards
what week do the testes begin to develop in genetic males
week 6-7
what week do ovaries begin to develop in females
week 9
female gonads consist of what cells and function
germ cells: produce oogonia
granulosa cells: surround an protect oogonia with stroma
theca cells: produce progesterone and with granulosa cells synthesize estradiol
secretion of GnRH begins week ____ but levels remain low until puberty. FSH and LH begins ___ and ___ weeks which remain low until puberty. During childhood ___ is higher than __
4
10 and 12
FSH than LH
during adult reproductive period the secretion becomes ___ and ___ is secreted in higher amounts than ___
pulsatile, LH>FSH
during the senescence stage what is secreted more FSH or LH
FSH
what is one of the earliest events of puberty
appearance of large nocturnal pulses of LH during REM sleep
the increased circulating levels of the sex steroid hormones are responsible for the appearance of what
secondary sex characterisitcs at puberty
GnRH analogue administered in intermittent pulses =
-long activing GnRH analogue administered =
- puberty is initiated and reproductive fnct is established
- puberty is not initiated
what is a physiologic cause of the increased secretion of FSH and LH
GnRH receptor in the anterior pituitary becomes more sensitive so this causes greater stimulation of secretion
what may be a natural inhibitor of GnRH release
melatonin
what are the two main functions of testes
spermatogenesis and secretion of testosterone
where is the primary location for the maturation and storage of sperm
epididymis
function of vas deferens
provides another storage area for sperm
-secretes fluid rich in citrate and fructose
FC Vas Deferens
seminal vesicles secrete what
FF PC
fibrinogen, fructose, prostaglandins, citrate
prostate gland secretes what
milky aqueous sltn rich in citrate, enzymes, and calcium
what is the blood testes barrier
formed by sertoli cell tight junctions
- selective permeability
- testosterone can cross but not noxious substances
what are the 3 androgens secreted by the testis
testosterone, DHT, androstenedione
fetal leydig cell function
masculinization of the male urogenital tract and inducing testis descent
-cells atrophy shortly after birth and don’t contribute to adult leydig cell pop
adult leydig cells formation
derive from undifferentiated precursors present after birth, become fully steroidogenic at puberty
how do leydig cells make cholesterol
de novo
- also get from circulation via LDL receptors and sometimes HDL
- they have it stored as cholesterol esters and release it to free cholesterol with HSL
what enzymes do the testis lack that prevents glucocort or mineralcort syn
21-B hydroxylase
11-B hydroxylase
in the lumen of the seminiferous tubules testosterone is concentrated by binding
androgen-binding protein
in what tissue is DHT the active androgen
SLEP
skin, liver, external genitalia of the male fetus, prostate gland
what is most of the circulating testosterone bound to
plasma proteins such as SHBG and albumin
___ stimulates syn of SHBG ___ inhibits
estrogens stim
androgens inhib
where in the male is the estrogen levels high and what may be the source
in the seminiferous tubules it is high
- sertoli cells may convert testosterone to estradiol via aromatose
- could play role in spermiogenesis bc sperm cells have isoform of estrogen receptor
where is 80% of estrogens formed from in the male
the liver
what is another name for P450SCC
cholesterol desmolase
leydig cells make testosterone then what happens
Testosterone diffuses both into the neighboring seminiferous tubules and into the peritubular capillary network to be carried to peripheral circulation
- in tubules T concentrated by binding ABP
- T carried to periphery by SHBG
the leydig cells makes limited amount of ___ and ___ which is made much more by ___
DHT and estradiol-17B
-these are usually made more by peripheral conversion
how does LH promote pregnenolone synthesis
- increases affinity of desmolase enzyme for cholesterol
- long term action stimulates synthesis of desmolase enzyme
what kind of receptor is the androgen receptor
nuclear receptor
deficiency of 5a-reductase causes what
ambiguous external genitalia
50% of excreted androgens are found as what
urinary 17-ketosteroids
testosterone action during fetal development
\+test = penis, scrotum -test = clit, vag
- internal male genital tract = seminal vesicales, epididymis, vas deferens
- causes descent of testes into scrotum during last 2-3 months of pregnancy
specific actions of DHT
fetal differentiation of external male genitalia (penis, scrotum, prostate)
- male hair distribution and male pattern baldness
- sebaceous gland activity
- growth of prostate
LH binds LH receptor on leydig cell: molecular mech
coupled to Gs
- cAMP and PKA, leads to testosterone production
- testosterone diffuses into seminiferous tubules and peripheral circulation
sertoli cell stimulated by what and pathway
FSH and testosterone
- binds, linked to Gs, cAMP and PKA, produces inhibin which inhibits FSH release
- FSH also stimulates sertoli cells to secrete ABP into lumen of sem tub which binds testosterone and provides local supply of testosterone for developing spermatogonia
sertoli cell can also convert ___ to ___ bc it produces what
testosterone to estradiol bc it makes aromatase
functions of sertoli cells
supportive, exocrine, and endocrine
fnct of sertoli cells; supportive
-maintain blood-testis barrier
-phagocytosis
-transfer of nutrients from blood to sperm
receptors for hormones and paracrines
fnct of sertoli cells: exocrine
produce fluid and ABP
-determine release of sperm from seminiferous tubule
fnct of sertoli cells: endocrine
- express testost, ABP and FSH receptors
- produce AMH
- aromatization of test to estradiol 17B
- produce inhibin to regulate FSH levels
inhibin from sertoli cells feeds back on what?
anterior pituitary gland
seminiferous tubules have 2 sets of cells
spermatogenic cells that develop into spermatozoa
-sertoli cells which have supportive and nutrient function
hormonal factors that stimulate spermatogenesis
- LH: leydig cells secrete test
- Testosterone: growth and division of testicular germ cells
- FSH: sertoli cells nurse and form sperm
- estrogens: may be essential for spermatogenesis
- GH: promotes early division of sperm
functions of seminal vesicles
prostaglandins
secretions add nutrients to sperm
- prostaglandins aid in fetilization by reacting with femal cervial mucus to make it more receptive to sperm movement (make it less thick)
- cause backward reverse peristatltic contraction in uterus and fallopian tubes to help move ejaculated sperm towards ovaries
function of prostate gland
secretes thin, milky fluid that contains Ca2+, citrate, and enzymes
-alkaline fluid helps neutralize acidity of other seminal fluids during ejac
what is the pH of semen
7.5
steps in erection
parasymp nerves innervating vascular SM of helicine arteries that supply blood to cavernous spaces release NO
- NO activates guanylyl cyclase, increases cGMP and decresases intracell Ca2+ = relaxation of SM
- vasodilation allows blood in and causes engorgement and erection
- engorged tissue presses veins against no compliant fascia to prevent drainage
- somatic stimulation increases contraction of muscles at base of penis, further promoting erection
emission of semen
under symp control (adrenergic transmitter)
- causes sequential peristaltic contraction of SM of vas deferens, while closing internal sphincter of bladder
- prevents retrograde ejac into bladder
- emission normaly precedes ejaculation but also continues during ejaculation
ejaculation
propulsion of semen out of male urethra
-rhythmic contraction of bulbospongiousus and ischiocavernousus muslces
both innervated by somatic motor nerves
capacitation of spermatozoa
when sperm first expelled in semen can’t fertilize ovum
-change occurs when they come in contact with fluids of female tract
changes of sperm during capacatiation
- uterine and fallop tubes wash away inhib factors
- loss of cholesterol which was built up on acrosome, which now make head of sperm weaker
- membrane of sperm more permeable to calcium, increases motility
sperm acrosome reaction
stored in acrosomal head of sperm are large quant of hyaluronidase which breaks hyaluronic acid polymers that hold ovarian granulosa cells together
-enzymes digest proteins in the strucutural elements of tissue cells that adhere to ovum
gonadal dysfunction in male 2nd to 3rd month gestation
ambiguity in male genitalia and male pseudohermaphrodism
GD in male 3rd trimester of pregnancy
leads to problems in test descent and micropenis
GD during puberty
poor 2ndary sex development and eunuchoid features
-prepubertal charact, and often by presence of charact typical of opp sex
GD post puberty
decreased libido, ED, decreased facial and body hair growth, low energy, infertility
klinefelter syndrome
men with extra X chrom
- androgen production low (variable)
- levels of gonadotropins are elevated, indicate primary hypogonadism
- seminif tubes destroyed, infertility
andropause
as men age gonadal sensitivity to LH decreases and androgen production drops
-FSH and LH levels rise
secondary hypogonadism: pituit dys
decreased LH and FSH = decreased T
secondary hypogonadism: hypothal dys
decreased GnRH leads to decreased LH and FSH and therfore decreased T
