spermatogenesis Flashcards
what are the two compartments of the seminiferous tubules
intratubular compartment peritubular compartment (interstitial space)
what cells surround the developing sperm
sertoli (sustentacular)
what is found in the interstitial space of the seminiferous tubules
Leydig cells
blood and lymph vessels
what is the purpose of the blood testis barrier
prevents immune reaction to spermatozoa
separates fluid of different composition
what are the 3 stages of sperm production
mitosis
meiosis
cell modeling (spermiogenesis)
how often does spermatogenesis happen
every 16 days
how often does the first mitotic division happen
every 74 days
what happens at the end of differentiation
cytoplasmic links broken
spermatozoa released into tubule lumen
sperm are virtually immobile
what does the acrosome contain
enzymes for fertilisation
what does the midpiece contain
mitochondria
where does spermatogenesis begin
basement membrane
how many spermatogonia do males have
finite number but can undergo mitosis indefinitely
where do spermatids go after production
fluid secreted by sertoli cells flushes them through from seminiferous tubules to rete testes to epididymis
at what point are the sperm able to move
when they reach the tail of the epididymis
what is capacitation
occurs in female genital tract
takes approx 4 hours
glycoprotein coat is stripped
this causes hyperactivation and head is able to initiate the acrosome reaction
what proportion of sperm must be normal in order for in vitro fertilisation to occur
15% at least
what is normal sperm count
50 -150 x10^6/ ml
i.e. approx 100 million
what sperm count is defined as sub fertile
fewer than 20 million
what proportion of sperm from a normal donor show abnormalities
30%
what is oligozoospermia
low sperm count
what is the name for absence of sperm in ejaculate
azoospermia
what is the name for low sperm motility (fewer than 50% are moving)
asthenozoospermia
what is the name for a high proportion of abnormally shaped sperm
teratozoospermia
what are antisperm antibodies
abnormal immune response to sperm
what is testosterone converted to
dihydrotestosterone or estrogens
what cells produce estrogens
sertoli and leydig
what cell produces inhibins (controls hormone levels)
sertoli cells
what cell produces oxytocin
Leydig cells
causing contraction of smooth muscle of the genital tract
what are the stages in steroid hormone biosynthesis
acetate cholesterol progesterone testosterone estrogens
what happens if circulating testosterone is low
fewer cells undergo divisions but process takes the same length of time
how does the anterior pituitary gland control testicular function
secretes gonadotrophins from gonadotroph cells
what controls pituritary gonadotrophs
hypothalamus which secretes gonadotrophin releasing hormone
what is the blood supply of the hypothalamus and pituritary
inferior and superior hypophyseal artery
where are LH and FSh produced (gonadotrophs)
anterior pituitary- basophilic cells
where are lactotrophs (prolactin) produced
acidophillic cells in the anterior pituitary gland
what type of molecule are gonadotrophs
glycoprotein
what type of molecule are lactotrophs
polypeptides
what does the posterior pituritary secrete
arginine vasopressin (AVP) aka ADH and oxytocin (peptides)
what controls LH and FSH secretion
GnRH
what are the features of GnRH
GnRH is released into the portal
blood in pulses every hour
GnRH must be pulsatile or it is
ineffective
what pulse style favours LH synthesis and secretion
high amplitude and frequency
what pulse style favours FSH
Low pulse amplitude and frequency
what is the function of LH in males
stimulates testosterone from Leydig cells
how does FSH affect sperm production
essential for maintaining sperm production at its normal level
acts on sertoli cells
what is the function of prolactin in males
enhances LH receptors in leydig cells which increases testosterone and spermatogenesis
what hormones are produced by Leydig cells
oestrogen
oxytocin
testosterone
what hormones are produced by sertoli cells
oestrogen
inhibins
what is the function of ABP, androgen binding protein
binds to androgens in the testes which increases their concentration
