Test 2: 21 male repro Flashcards
in males during puberty, the — becomes — sensitive to the negative feedback form gonads
hypothalamus
less
* GnRH, FSH and LH↑ which causes the gonads to release more steroid hormones and 2ndary sex characteristics develop
how does hormone production change during puberty
hypothalamus becomes less sensitive to the negative feedback from gonads
Sertoli cells stop producing many ‘prepubertal’ genes eg —.
AMH
Males normally maintain a population of — that can repopulate the gonad throughout life.
diploid spermatogonia (spermatogonial stem cells)
can make sperm for life
how to regulate male fertility
seperate male and females
castration
vasectomy
hormones and vaccines- but they do not work well
LH acts on what cells
male- leydig- make testosterone
female: theca cells- make androgens
FSH acts on
male: sertoli cells- prepubertal sertoli cell proliferation, initiation of spermatogenesis, high in castrated males
female: granulosa cells- make estrogen
what happens to FSH levels after castration
will increase due to lack of inhibition on the hypothalamus
testosterone is maintained at high levels in the seminiferous tubules by
androgen binding protein
testosterone will have a — effect on FSH and LH
negative feedback
DHT is made in the — by —
- testosterone is made by leydig cells, then transfers to the sertoli cell and with 5 ⍺ reductase becomes DHT
DHT works on —
external genitalia and prostate
testosterone works in the leydig cells to —
stabilize the wolffian ducts
* epididymis
* vas deferns
* seminal vesicles
* internal male tract
estrogen is made in males by
in sertoli cells from testosterone
* will create a negative feedback on LSH and FSH and prolactin to inhibit spermatogenesis
* in horse and pig estrogen levels are higher in males than in females
how does inhibin work
made by sertoli cells- negative effect on FSH- related to germ cell numbers
- high FSH= bad (loss of inhibition from sertoli cells meaning few germ cells)
- fewer germ cells= less inhibin= more FSH
- ↑ # spermatogenic cells= make ↑ inhibin = ↓FSH = less germ cells made
- sertoli cells making ↓# germ cells= less inhibin made= ↑FSH= more germ cells made/drive spermatogenesis
high number of spermatogenic cells will do what to levels of FSH and inhibin
inhibin made by sertoli cells
more cells= more inhibin
* negative feedback on FSH= ↓FSH
* this will cause a decrease in amount of germ cells made
↑ # spermatogenic cells= make ↑ inhibin = ↓FSH = less germ cells made
sertoli cells making ↓# germ cells= less inhibin made= ↑FSH= more germ cells made/drive spermatogenesis
why does giving testosterone not result in increased sperm production
need androgen binding protein (ABP) in sertoli cells to bind to T, DHT and estrogen in the seminiferous tubules and epididymal lumenae
- systemic T is not physiologic
- increased levels of T will have opposite effect of ↓FSH and LH and will cause testicles to shrink
Removal of testis removes negative inhibition so FSH and LH — in castrated animals.
increase
development of surge center in female
estrogen can’t get into brain and surge center develops
surge center in males
T can get through BBB and is converted to E2 this will block development of surge center in the brain
short day breeders are — and respond to a — in melatonin
sheep and goats
increase
long day breeders are — and respond to a — in melatonin
horse and cat
decrease
what are some nonseasonal breeders
pigs, cattle, dogs
where are the leydig cells
in the intersitial tissue- outside the seminiferous tubules that have the sertoli cells
spermatocytogenesis
from diploid spermatogonia through mitosis and meisosis -2nd spermatocyte (halfloid)
spermiogensesis
differentiation of round spermatids to sperm
explain blood testis barrier
sertoli cells hold together and prevent things other then dividing sperm to get into the adluminal compartment of the seminiferous tubules
duration of spermatogenesis
- 34-60 days (species specific)
- takes 10-15 days to travel through epiidiymis
- type A spematogonia → ejactulated sperm 50-60 days
— connects the tail of the epididymis with the pelvic urethra
ductus deferens
what is the ampullae
at the end of the ductus deferens- swollen/thickened area where sperm can be stored
path of sperm in the male
orientation of testes in
— can move testes for temp control
tunica dartos, cremaster muscle
— pulls the teste into the scrotum
gubernaculum
when do testes descend in bull,ram and buck
mid-gestation
when do testes descend in boar
90 days of gestation
when do testes descend in stallion
late gestation to early post natal
when do testes descend in dogs and cats
post natal up to 6 weeks
* retained at 16 weeks
4 accessory sex glands
ampullae
vesicular glands
prostate
bulbourethral (cowpers) gland
what does seminal plasma do
- adds volume, sugar/energy for sperm
- initiates motility
- helps protect against female immune system
- uterine contractions?
what is the ampullae
thickening of the ductus deferens before it inserts at the urethra- sperm storage
- big in stallion, small in bull and dog
what are the seminal vesicles
- contribute 50% of bull semen and 20% for boar
- gel fraction in stallion
- not in carnivores
what is prostate
present in all species
* provides entire seminal fluids in dogs and cats
bulbourethral glands produce —% of — semen
20% of boar
ampulla and seminal vesicles empty into the urethra at the
colliculus seminalis
how to get erection
- ↑ bloodflow from pudendal artery causes cavernous tissue to swell, colapsing the venous drainage
- controlled by parasympathetic NS → spinal reflex mediated by pudendal nerve
- nerves release NO which causes ↑ G cyclase → ↑cGMP → erection
- after PDE 5 will cause a ↓ in cGMP
how does viagra/sildenafil work
blocks PDE5 which results in an increase of cGMP= longer erection
what causes ejaculation
alpha adrenergic sympathetic
* causes muscular contractions and closes the bladder neck
where is sperm deposited
ruminants, primates, cats - vagina
horse, pig, rodents, dogs- intrauterine/cervix
what happens to sperm in the oviduct
- can be stored
- then released in waves
- hyperactivate/capacitate after release
- only live short time to find egg
