Male Reproductive System Flashcards
major functions of adult testes
spermatogenesis
steroid hormone synthesis
steroid hormone synthesis in male testis occurs where
leydig cells
spermatogeneis (when does it occur)
begins at puberty and continues well into senescence
lower temp of testis is critical for what
normal spermatogenesis
majority of estradiol in males is made where and from what
adipose tissue from testosterone
androgens produced by testis are (which one is major)
testosterone (major)
androstenedione
DHEA
testosterone is bound to what
sex hormone-binding globulin (SHBG)-40-60%
albumin
what testosterone is bioavailable
free (2-3%)
bound to albumin (40-60%)
LH receptor (what is it)
G-protein coupled receptor
activates cAMP pathway
the LH receptor activates PKA which phosphorylates what to increase transcription of genes involved in steroidogenesis
CREB
LH caused phosphorylation of CREB increases traslocation of what genes
StAR
CYP 11A (P450scc)
CPY 17 (17-alpha-hydroxylase/17,20lyase)
proteins/enzymes in cholesterol synthesis and uptake
what happens to newly synthesized androgens
diffuse to neighboring seminiferous tubules and into capillaries where they enter systemic circulation
testosterone can be converted into what
other biologically active steroids
excretory metabolites
in some tissues testosterone is converted to what more potent androgen and by what
dihydrotestosterone (DHT) by
5-alpha-reductase
give an example of an androgen effect that requires DHT not testosterone
virilization of external genitalia during embryonic development
5-alpha-reductase inhibitors are useful for what
treating benign prostatic hyperplasia and prostate cancer
testosterone can be metabolized by an aromatase enzyme to form what
estradiol
where does aromatization of testosterone occur
certain CNS nuclei
Leydig and Sertoli Cells
adipose tissue
inactivation of testosterone occurs primarily where
liver
elimination of testosterone is enhanced if it is conjugated to what
glucuronic acid or sulfate
leydig cells differentiate from what type of cells when
mesenchymal cells during weeks 8-9
primary stimulus for early leydig cells is thought to be
hCG
when do gonadotropins appear to be affecting testosterone secretion
mid-gestation
levels of testosterone during childhood are what (whens the exception)
relatively low except at neonatal surge
the rise in testosterone during puberty corresponds to a rise in plasma concentrations of what
LH
what does LH do
promotes androgen biosynthesis in Leydig cells
what happens to androgen production in males over time
age-related decline in total serum testosterone begins 4-5th decade of life
what age-related event in males leads to a further decrease in bioavailable testosterone in men
age-related increase in SHBG
what type of receptor is the androgen receptor
ligand-activated transcription factor
androgen receptor has highest affinity for what
DHT
the androgen receptor binds DNA when
hormone is bound to its appropriate binding site on receptor
in the fetus androgens do what
promote the differentiation of male reproductive tract and external genitalia
at puberty androgens do what
promote growth and maturation of reproductive structures
development of male secondary sexual characteristics
in adult androgens do what
maintain functional integrity of reproductive system
enlargement of larynx and thickening of vocal cords
androgens promote what in terms of proteins
anabolism
androgens regulate what
spermatogenesis
in both genders androgens do what
promote hair and sebaceous gland growth
actions of androgens that aren’t age specific
behavioral effects and libido
stimulate erythropoietin synthesis (increased hematocrit)
negative feedback on gonadotropin release
bone growth
testosterones actions on bone growth are mediated by what
estradiol
testosterone (via estradiol) promotes bone growth how
stimulate GH release
stimulate pubertal growth spurt
promote closure of epiphyseal plate
what lines the basal lamina of seminiferous tubules
Sertoli cells
principle function of sertoli cells is what
transfer nutrients from developing germ cells and create and environment that is conducive for germ cell differentiation into mature spermatozoa
what divides seminiferous tubules into two functional compartments
tight junctions between sertoli cells
the tight junctions b/w sertoli cells form what
“blood-testis” barrier
as primary spermatocytes migrate from basal compartment into adluminal compartment what happens
tight junctions disassemble and reassemble
what do sertoli cells phagocytize
cytoplasm released by spermatozoa during spermiogenesis
sertoli cells secrete what
Androgen Binding Protein (ABP)
Anti-Mullerian Hormone (AMH)
Inhibins and activins
Estradiol
Androgen Binding Protein (ABP)
what is its function
serves to keep testosterone levels elevated in the seminiferous tubules and epididymis
ABP secreted from sertoli cells has the same structure as what
sex-hormone binding globulin from liver
what stimulates ABP secretion from sertoli cells
testosterone and FSH
sertoli cell function can be assessed by what
ABP secretion
Inhibin B
sertoli cells secrete what that are members of the TGF-beta family
AMH
activins
inhibins
AMH (what does it do)
regression of mullein ducts in the male embryo
AMH (signal is transmitted how)
2 transmembrane serine-thronine kinase receptors
AMH binds what receptor
type II serine-threonine kinase
type II serine-threonine kinase receptor (what special about it)
constitutively phosphorylated receptor
AMH-bound type two receptor does what
recruits a type 1 receptor and phosphorylates it
phosphorylation of type 1 receptor by AMH bound type II receptor does what
activates kinase activity
activated type 1 serine-threonine receptor does what
phosphorylates Smad3
phosphorylation of Smad3 does what
unmasks its nuclear localization signal
phosphorylated Smad3 forms complex with what
other cytoplasmic proteins including non-phosphorylated co-Smad protein Smad4
complex of Smad3 and Smad4 does what
translocates to nucleus where it regulates transcription of genes that promote apoptosis
inhibins and activeness are what (in terms of structure)
dimers formed from different combinations of 3 distinct subunits held together by disulfide bonds
Inhibin B (what is it)
principle circulating inhibin in males
plays role in feedback regulation of FSH
what stimulates inhibin B production
FSH and testosterone
inhibin B what is its effect
blocks GnRH-stimulated FSH release by gonadotropes
E2 is formed how
aromatization of androgens in response to FSH stimulation
what are the 3 phases of spermatogenesis
mitosis to increase number of spermatogenic
meiosis to provide haploid spermatids
spermiogenesis to transform immature spermatids to matrue spermatozoa
what is required to be functional for normal spermatogenesis in adults
functional Sertoli cells and intact hypothalamic-pituitary-gonadal axis (pulsatile release of GnRH)
what is important about the deliver of GnRH
pulsatile fashion
the principle target of FSH action is
spermatogonia
FSH actions
stimulates inhibin synthesis
what hormones are necessary for spermatogenesis
LH
FSH
testosterone
in human male what is only known cell to express FSH receptor
sertoli cell
FSH and testosterone work how together
synergistically
testosterones role in spermatogenesis
local regulator
low levels of intratesticular testosterone do what
result in decreased sperm production
blood-epididymis barrier (what is it made from)
tight epithelium of epididymis
how long to sperm spend maturing and where
a month
epididymis
what happens to spermatozoa in epididymis
coated with substances that block acrosomal reaction (decapacitation)
decapacitation (what is it)
sperm not having acrosomal action
sperm storage sites are
epididymis
vas deferens
Kallman Syndrome (what is it)
form of hypogonadism caused by failure of GnRH secreting cells to migrate from olfactory placode to hypothalamus during embryogenesis
Kallman Syndrome (signs/symtoms)
Low circulating levels of gonadotropes
Symptoms of androgen deficiency become apparent at puberty and arrested spermatogenesis
release of pituitary gonadotropin is a function of what
concentration and pattern of GnRH release
normal secretory activity of gonadotrope requires what
intermittent delivery of GnRH
continuous exposure of GnRH does what to gonadotrope activity
suppresses it
“functional castration”
gonadotropins are released in what kind of pattern
pulsatile
secretory bursts
onset of puberty is associated with what
sleep associated surge in LH release
what is puberty
transition period where secondary sexual characteristics and reproductive competence develop
adolescent growth spurt also happens
in neonate HPG axis is under what control
CNS
what happens during puberty in terms of HPG axis
removal of CNS inhibitory effects on the activity of GnRH- releasing neurons
hypothalamic and pituitary changes associated with puberty are
decrease in sensitivity to the negative feedback of testosterone
increase amplitude of GnRH pulses
increase in sensitivity of gonadotropes to GnRH
during childhood the HPG axis is what
relatively quiescent
rising gonadotropin levels in the testes does what
promotes leydig maturation and secretory activity
promote differentiation and maturation of sertoli cells
initiate onset of spermatogenesis
increase in testicular volume
what promotes the anatomical and physiological changes normally associated with puberty
increase in circulating levels of testosterone
Stage 1 puberty in boys is
preadolescent development
Stage 2 of puberty in boys is
period where testes begin to enlarge
first clinical manifestation of puberty in boys
enlargement of testes
stage 3 of puberty in boys is
enlargement of penis
stage 4 in puberty in boys is
growth of glans penis
stage 5 of puberty in boys is
adult genitalia
what acts at the level of hypothalamus and may be important link b/w nutritional status and reproductive competence
leptin
what inhibits the hypothalamic pulse generator
testosterone
inhibit does what
inhibits FSH release
in the flaccid state what are the helicine arteries like
constricted (minimal blood flow)
what supplies the cavernous spaces of the penis with blood
helicine arteries
what covers the corpora cavernosa
tunica albuginea
rigidity of erection depends on
increase in flow of arterial blood (parasympathetics)
decreased venous efflux from compression of venous plexus
erectile response is ignited how
tactile (low motor neuron reflex) or psychic (mediated over corticospinal pathways)
afferents of erection are transmitted how
pudendal nerve
efferent parasympathetic fibers do what
vasodilator the helicine arteries and sinusoidal spaces
efferent parasympathetics realize what vasodilatory for erection
NO and VIP
what can be used to treat erectile disfunction
cGMP specific phosphodiesterase inhibitors
mucus is secreted from what during sexual stimulation
urethral and bulbourethral glands
mucus secretion during sexual stimulation is mediated by what
parasympathetic nerves
what is emission
moment of semen into proximal part of urethra
emission involves what
coordinated rhythmic contractions of vas deferens, ampulla, prostate, and seminal vesicles
inhibin has what effect on LH
little or no
what mediates emissions
sympathetics in upper lumbar region of spinal cord
the mediation of emission is done how
norepi released on alpha 1 receptors
function of internal urethral sphincter in ejaculation
sympathetics constrict it preventing retrograde into the bladder
filling the urethra with semen does what
elicits sensory signals from pudendal nerve in the sacral portion
when in emission/ejaculation is the sacral portion of the spinal cord used
filling of urethra with semen
when in emission/ejaculation is the lumbar portion of the spinal cord used
mediating emissions
hypogastric nerve
what triggers the rhythmic contraction of the started musculature of perineum
efferent signals from somatic efferent fibers in pudendal nerve
male orgasm is what
conscious awareness of contractions associated with ejaculations
systemic changes associated with male sexual response
increase in:
rate of respiration
heart rate
blood pressure
sympathetic stimulation of emission is done by what type of fibers and what neurotransmitter and what receptors
sympathetics
norepi
alpha 1
clinical manifestations of testicular dysfunctions are
infertility
decreased libido
lack of development of secondary sexual characteristics
testicular dysfunction before puberty (what features are apparent)
abnormal skeletal proportions gynecomastia sparse pubic, axillary, and facial hair high pitched voice infantile genitalia poorly developed musculature
Gynecomastia (what is it)
estrogens have stimulatory effects on breast tissue while testosterone has inhibitory
so if a male has excessive estrogen exposure or decreased testosterone can get this
causes of primary hypogonadism
Klinefelter Syndrome
Orchitis
Irradiation
orchitis (what is it)
inflammation of testes
usually secondary to mumps
seminiferous tubule destruction
leydig cells not affected
irradiation of testicles affects what
seminiferous tubules more sensitive to irradiation than leydig cells
describe FSH, LH, estradiol, and testosterone levels in a patient with klinefelter
FSH and LH high
testosterone normal to low
estradiol high
what reproductive disorder is often associated with defective sense of smell
kallman
what reproductive disorder is often associated with fibrotic of hyalanized seminiferous tubules
klinefelter syndrome
