physiology- male Flashcards
what % of men is affected by infertility in UK?
impaired spermatogenesis affects what % of them?
6%
90%
what % of conceptions is affected by abnormal meiosis & meiosis?
what % of livebirths are affected by above?
7%
0.7&
what is the function of testes?
produce & store sperm
produce hormones
how much below body temp is the optimum temperature for production of sperm?
1.5-2.C
overheating of testes reduces sperm count
normal size and volume of testes?
3.5-5.5 cm long
2.0-3.0cm wide
15-30mL = volume
male reproductive tract structure:
ASPC
ampulla
seminal vesicle
prostate
Cowper’s gland
testes structure:
which part of testis is the site of spermatogenesis?
what % of testes is this?
how does it all fit
seminiferous tubules
90% of testes = seminiferous tubules
- tubules are tightly coiled to create large surface areas = lobules
what do seminiferous tubes’ lobules feed into?
what does this structure lead into?
rete –>epidydimis & vas deferens
what are the walls of the seminferous tubule made of?
what kind of cells are these?
Sertoli cells
tall columnar endothelial cells
what cells lie on the basement membrane between Sertoli cells?
what are spaces between the cells filled with?
spermatogonia (primary germ cells)
- blood
- lymphatic vessles
- Leydig cells
- intersitial fluid - v high volume, would be considered oedemic in any other tissue
what layer is there in addition to basal lamina to protect from infection?
tight junction
role of tight junction (where exactly is this??)
- opens to allow passage of spermatogonia prior to completion of meiosis
- provides luminal and adluminal compartment
- protects spermatogonia from immune attach
- allows specific enclosed environment for spermatogenesis which is filled with secretions from Sertoli cells
spermatogenesis stages:
(names of cell)
- spermatogonia = sperm cell on basement membrane.
capable of meiotic and mitotic divisision
i.e. produces primary spermatocytes ot more spematogonia - spermatocyte
- committed to differentiative pathway
primary spermatocyte = 46XY
secondary spermatocytes have divided meiotically to 23X + 23Y - spermatid
- 2nd division occurs to give 4 round spermatids - spermatozoa
= mature sperm extruded into lumen
what controls movement of sperm cells into lumen?
Sertoli cell secretion
how long does sperm development take?
how frequent is a new wave?
74 days
every 16 days
oogonia vs spermatogonia
i. laid down as foetus
ii. fate of each germ cell
iii. supply finite/ infinite
i. both
ii. A begin meiosis to make oocyte
B begin meiosis to make spermatocyte or divide mititically to make more spermatogonia
iii. finite supply oogonia, infinite supply spermatogonia
hypotholamic/ pituitary/ gonadal axis in male
-ve feedback only
Leydig cell
i. which receptors are present?
ii. what is converted to what?
i. LH receptors (and oestrogen receptors)
ii. cholesterol –> androgens
LH stimulates Leydig cells to produce testosterone via what?
cAMP
in foetus testosterone production by Leydig cells is under control of which hormone?
hCG
where within testes do androgens produced in Leydig cells go?
what is their role?
cross over to Sertoli cells
control of spermatogenesis (by stimulating Sertoli cell function)
what can happen to testosterone released into circulation? (2)
- –> estrone and estradiol in skin and adipose tissue
by aromatase - reduced –> more active dihydrotesterone in peripheral target tissues
by 5-alpha-reductase
Sertoli cells
i. receptors present
ii. reaction which occurs
iii. which protein do Sertoli cells produce to concentrate testosterone?
i. FSH receptors (and androgen receptors)
ii. androgens –> oestrogen
(by aromatase)
androgens –> DHT
iii. androgen-binding protein
2 hormones needed for spermatoigenesis
FSH, testosterone
other roles of testosterone:
- maintenance of prostate, seminal vesicles, ampulla and bulbourethral gland
female equivilent of:
i. Leydig cells
ii. Sertoli cells
i. theca cells
ii. granulosa cells
where does most E2 (oestradiol)come from:
i. prepuberty
ii. in adult
i. Sertoli cells
ii. Leydig cells
both are needed to initiate spermatogenesis
LH alone may be sufficient to re-initiate
testosterone levels in testes vs in plasma?
in testes 100x those in plasma
what hormone alone may be used to re-initiate spermatogenesis in hypotrophic hypogonadism in adult?
LH
effect of exogenous steroids on -ve feedback:
- testes shrink
- hypotrophic hypogonadism (i.e. -ve feedback to hypothalamus is overwhelmed???)
spermatozoan structure
3 main parts:
- head
- acrosomal cap
- postacrosomal region - middle piece
- microtubules = machinery of motility
- mitochondira = energy of motility - tail
- principle piece
- end piece
where do mature spermatoza collect & pass onto?
rete, pass onto epididymis
length of epididymis?
how long does it take sperm to pass?
3 parts of epididymus?
5m
8-14 days
caput (head) = start of maturation
corpus (body) = completion of maturation.. mobility
cauda (tail) = main site of storage
individual ducts of epididymis join to make vas deferens
what causes erection?
which nervous system is involved?
vasodilation of the corpus cavernosum
autonomic - causes co-ordinated contractions of vas deferens and glands
afferent/ efferent nerves involved in erection:
afferent: internal pudendal nerves
three efferent outflows: the parasympathetic pelvic nerve (stimulatory)
the sympathetic hypogastric nerve (inhibitory and some stimulatory
fibres)
somatic pudendal nerve (stimulatory)
in erection/ ejaculation what is the role of:
i. sympathetic control
ii. parasympathetic control
i. sympathetic:
- movement of sperm into epididymus, vas deferens, penile urethra
ii. parasympathetic control
- erection and evacuation of urethra
seminal fluid
consists of secretions from which 3 glands?
+ which other fluid
seminal vesicles
prostate
bulbo-urethral gland
+epididymal fluid
ejaculate fluid reference values:
i. volume
ii. concentration
iii. progressive motility (i.e. % which must be forwards moving)
iv. normal forms (i.e. appear normal under microscope)
i. volume 1.5mL
ii. concentration 15million/mL
iii. progressive motility 32%
iv. normal forms 4%
how is entry of semen into urethra prevented?
contraction of urethral sphincter
getting to vagina:
- seminal fluid coagultes in vagina
- prevents loss, later requalifies
- seminal fluid changes acidic pH to alkali (from 3-4 to 7.2) - sperm passes into cervix (mucous changes)
- glycoproptein molecules arrange in parallel lines (aggregates)
- micelles vibrate and aid passage of motile sperm
- non-alginates sperm form reservoir in cervical crypts
name of 2 changes sperm undergo when passing into uterus/ coming in contact with uterine fluid:
- capacitation
- acrosome reaction
what happens during capacitation?
why?
what initiates capacitation
biochemical removal of the surface glycoprotein - this initiates whiplash movement of tail - sperm become more hyperactive
helps to reach and penetrate egg
uterine/ uterine tube fluid
what is the purpose of the acrosome reaction?
allows sperm to male slit in zona pellucida (outer layer of egg) after binding to it
what cell layer protects the egg?
what do these cells secrete?
cumulus cells
mucus matrix
what causes zona pellucida secretions to withdraw?
LH surge
at this point 1st meiotic division resumes and completes
extra chromosomes are packaged into 1st polar body
by which process is the sperm taken into the ovum?
what causes migration of cortical granules in egg to zona pellucida?
phagocytosis
cortical granules migrate to edge and fuse with zone pellucida
calcium eaves arising from fusion
what happens as soon as 1st sperm enters ovum?
what is this process called?
membrane fusion
intravelline processing
what happens once the sperm and egg have fused?
male sperm –> male pronucleus
female 2nd polar body (remember meiosis 2 happens one sperm enters egg I think –> female pronucleus
2 join, mitosis
what is the blastocyst called once it reaches the 8-16 cell stage?
what are the 2 distinct cell types called by this stage?
morula
outer = trophoblast (develop into chorion/ placenta)
inner = cell mass
what does blastocyst secrete to prevent breakdown of corpus luteum?
hCG
interacts with LH receptors on corpus luteum
