Spermatogenesis Flashcards
(23 cards)
what’s composed in peritubular compartment
leydig cells
vasculature
what do leydig do
secrete testosterone
2 compartments of testes
how do we keep them separate?
- seminiferous tubules: developing germ cells. sertoli cells
- interstitial spaces:
leydig cells
blood and lymph
separated by blood-testis barrier
2 functions of blood-testis barrier
- prevents immune reaction to spermatozoe (as immune system develops before sperm)
- separates fluids of different composition - creates gradients
where is the blood-testis barrier
between seminiferous tubules and interstitial spaces - between neighbouring sertoli cells
zonular junctions and filament bundles
can a primary spermatocyte get through BTB?
yes
3 stages of spermatogenesis
primordial germ cell –> spermatozoa
- mitotic proliferation
(spermatogonia undergoes self-renewal mitotic division to replenish stem cell pool) - meiotic divisions
(primary spermatocyte enters meiosis 1. 46 chromosomes. DNA copy number 4C.–> secondary which has 23 chromosomes 2C. ) Further meiosis 2 –> 2 haploid chromosomes. (23 and 1C). - spermiogenesis (cell modelling)
spermatocyte -> spermatid –> head (acrosome and nucleus), middle piece, principal piece, end piece (9+2 microtubular arrangement)
from 1 spermatogonia you get
4 spermatozoa
what is spermiation
occurs at end of differentation:
- cytoplasmic links broken
- spermatozoa released into tubule lumen
- sperm virtually immobile
what does the sertoli cell do after spermiation
secretes fluid to flush from seminiferous tubules through rete testis to epididymis.
epididymal fluid
protects sperm perevents motility (aided instead by peristaltic contractions)
what process needs to occur (to sperm) for fertilisation to occur
CAPACITATION
normally occurs in female repro tract. glycoprotein coat is stripped.
- -> head acquires capacity to initiate acrosome reaction
- -> hyperactivation (increased flagellar beats)
normal semen volume pH sperm conc total sperm count total sperm motility (%) sperm morphology (% normal)
>1.5ml >7.2 >15 million >39 million sperm/ejaculate 40% motility >4% normal sperm
GnRH from where in what way stimulates what eg.
from hypothalamus
in pulsatile secretions
anterior pituitary gonadotrophs: LH and FSH control testicular functions
Rs for leydig
leydig cells have Rs. stimulates synthesis and secretion of testosterone.
What does FSH do?
required for max sperm reduction.
it acts on sertoli cells
how do we get oestrogen from testosterone
it is aromatised
effects of oestrogen on testes
produce hormone called inhibin.
if LOTS of testosterone: inhibin is produced (-> piuitary and decreases amount of FSH)
if low inhibin, what about levels of gonadotropin
high LH and FSH
functions of FSH on sertoli cells
increased RNA and protein synthesis increased energy metabolism increased cyclic AMP increased androgen receptors increased FSH receptors
increased fluid secretion
increased ABP secretion
increased inhibin secretion
what hormones do the testes synthesise?
- testosterone (steroid) by leydig cells
- oestrogens (steroid) by sertoli and leydig cells
- inhibins (peptide) by sertoli cells
- oxytocin (peptide) by leydig cells
when is testosterone blocked
when primary spermatocytes enter meiotic prophase
causal diagnosis of male infertility
10% is
14% is
4% is
28% infertile men are given causal diagnosis
10% previous gonadotoxic chemo or radiotherapy for treatment of malignant disease
14% testosterone abuse or other chronic disease (diabetes)
4% genetic disorders (Kleinefelter’s, microdeletions on Y)
