Reproductive Physiology of the Male Flashcards
what enzyme converts testosterone into estradiol
aromatase
what enzyme converts testosterone into DHT
5𝛼-reductase
what is de la chapelle syndrome
XXsry+
male internal and external genitalia but infertile due to lack of Eif2s3y gene
what does masculinization of the sexually dimorphic nucleus require
estradiol (E2)
testosterone produced in the testes converted to E2 via aromatase
what protects E2 from the female from entering the brain in the fetus
𝛼fetoprotein
3 parts of the male brain and what they are regulated by
- Libido - estradiol E2 (can be testosterone converting to E2)
- male behaviors (aggression, scent marking) - testosterone
- pulse generator - kisspeptin producing neurons w/ Testosterone, E2 and P4
explain the HPT axis
kisspeptin
GnRH
LH –> leydig cells, T production
FSH –> sertoli cells, inhibin, androgen binding protein and acts on sperm cells supporting mitosis/meiosis
days for spermatogenesis
60 days
days for epididymis travel
10-14 days
how do anabolic steroids affect reproductive function
5-10x T levels needed to maintain spermatogenesis
anabolic steroids only have 2-3x T = no spermatogenesis
what produces melatonin
precursor for melatonin
function of melatonin
pineal gland in absence of light
tryptophan
acts on pulse generator cells to regulate GnRH
how do animals regulate seasonal breeding?
melatonin
long day breeders (horse, wolf, fox, rodents, birds)
melatonin (-) kisspeptin
decreases GnRH
short day breeds (cattle, elk/deer, sheep)
melatonin (+) kisspeptin
increases GnRH
how does melatonin differ between males and females
males less affected - most species produce sperm year round
describe the effects on sperm with short term heat vs long term heat
short term heat - sperm abnormalities during spermatogenesis
long term heat - spermatogenesis ceases (e.g. cryptorchid)
Four Mechanisms of Thermoregulation
- arterioles/venous blood close to surface of skin of scrotum for dissipation
- sweat glands in skin of scrotum for evaporation
- pampiniform plexus (countercurrent exchange)
- tunica dartos & external cremaster muscle - contract/relax of scrotum and testes respectively
how does illness, stress and fat affect reproduction
illness - fever - elevated temp - negative effect on spermatogenesis
stress - cortisol - decreases kisspeptin - decreases T
fat - difficult thermoregulation in scrotum
at what temperature can spermatogenesis occur
temperatures 2-5 degrees
lower than body temp
describe cryptorchidism
no spermatogenesis
leydig cells functional - T produced
increased incidence of seminoma
heritable or environmental
describe spermatocytogenesis
occurs in basal compartment
spermatogonia > primary spermatocytes
describe meiosis I
primary spermatocyte > secondary spermatocyte
describe meiosis II
secondary spermatocyte > spermatid
describe spermiogenesis
occurs in adluminal compartment
no cell division
spermatids (round then elongated) > spermatozoa
what is critical for spermiogenesis? why?
Testosterone
because cells cannot make mRNA = no proteins
need sertoli cells to make enzymes and proteins via androgen binding protein maintain testosterone levels so cells can mature and progress
function of the blood testis barrier
protects developing sperm from immune system attack
what is unique about the stages in seminiferous tubules
see different stage in each seminiferous tubules on cross section - allows release of sperm everyday
what determines the shape and size of sperm heads in different species
proamines
what structure of the sperm head is responsible for penetrating/digesting the zona pellucida of the oocyte
acrosome
where are the centrioles located
neck region of sperm
what part of the sperm contains the mitochondria
midpiece
what is the cytoplasmic droplet
cytoplasms migrates down tail as sperm matures through the epididymis and is lost when sperm becomes motile
what occurs if the cytoplasmic droplet remains
problem in spermiogenesis or epididymal maturation → decreased fertility
what is the order of sperm transport to the epididymis
sertoli cell > seminiferous tubule > rete testis > efferent ducts > head of epididymis
what is the only part of the male reproductive tract that has cilia
efferent ducts
head of epididymis
muscle?
epithelium? villi?
fertility?
motility?
thin smooth muscle
more epithelium, long microvilli (bc majority of fluid is absorbed)
not fertile
not motile
body of epididymis
muscle?
fertility?
motility?
thin smooth muscle
not fertile
not motile
tail of epididymis
muscle?
epithelium? villi?
fertility?
motility?
large amount smooth muscle
less epithelium , short microvilli
fertile
not motile
when does sperm become motile
when mixed with seminal plasma due to water, proteins, sugars, salts, citrate/bicarb, gel
erection is parasympathetic or sympathetic
parasympathetic
ejaculation is parasympathetic or sympathetic
sympathetic
what 2 structures of the female require sperm motility
cervix
utero-tubule junction
NOT the uterus bc sperm moves via uterine contraction
what is capacitation and where does it occur
oviductal epithelium
loss of cholesterol, increase in IC calcium, loss of seminal plasma proteins coating the cell exposing receptor for zona pellucida
what induce the acrosomal reaction
zone pellucida proteins
what is the acrosomal reaction
release of acrosomal enzymes (ZP1, ZP2, ZP3) to expose receptor for oolemma so sperm (sumo 1) can bind to oolemma fusing sperm and oocyte membranes
methods of semen collection
artificial vagina “gold standard”
electroejaculation
chemical ejaculation
manual stimulation
