spermatogenesis Flashcards
role of testes
houses seminiferous tubules, site of spermatogenesis
epididymis
sperm storage and maturation
vas deferens
transport of sperm from epididymis to urethra during ejaculation
seminal vesicle
produces mucus secretion which aids the mobility of the sperm
prostate gland
produces an alkaline secretion that neutralises acidity of urine in urethra and aids mobility of the sperm
2 functions of testes
- produce sex androgens and other hormones for sexual differentiation and secondary sexual characteristics
- produce spermatozoa for sexual reproduction, occurs in seminiferous tubules
what does the stroma consist of?
blood vessels, lymph and leydig cells
what happens to PGCs around 6 weeks gestation?
PGC population expands by mitosis and migrates to the genital ridge primordium
what can happen if something disrupts mitosises of sertoli cells?
can get low sperm count
when does spermatogenesis begin?
puberty- about 10 million sperm produced per day
how are spermatogonial stem cells self-regenerating?
undergo rounds of mitosis
what morphologically distinct cells emerge at intervals?
type A spermatogonia
how are type B spermatogonia formed?
the type A produce a clone of 16 cells which enter further rounds of mitosis with some differentiation inbetween them
what dictates whether they divide or differentiate?
growth factors
what direction does development occur?
in a centripetal direction- from basement membrane towards lumen
what is spermiation
when fully differentiated sperm are released into lumen
how is the acrosome cap formed in spermiogenesis
formed from golgi
what else happens in spermiogenesis
the nucleus changes shape to fit in the head, one of the centrioles of the spematid becomes a tail, remaining excess cytoplasm and organelles are removed by sertoli cells via phagocytosis
when does X and Y chromosmomes transcription stop?
before meiotic divisions
when does autosomal transcription cease?
during spermiogenesis
what are histones replaced with in sperm?
protamines and the chromatin becomes condensed
what do sertoli cells form?
gap junctional complexes
what separates the basal and adluminal compartments
blood testis barrier formed by gap junctional complexes
which compartment is immune privaleged?
the adluminal one, so haploid cells not immune rejected
when do spermatogonia become spermatocytes?
once they enter meiosis and move away from the basement membrane and into the adluminal compartment
round and elongating spermatids are located where?
in adluminal compartment
how often does a section of seminiferous tubule produce a sperm? why
every 16 days. since it takes 64 days to complete spermatogenesis but there are 4 sperm developing at staggered points in the cycle
why are there populations at 4 different stages of development?
set lag time between development of SSC families
what provides a means for communication
gap junctions between adjacent sertoli cells provides a means for communication
3 main functions of testosterone in sertoli cells
- maintains blood-testis barrier integrity
- required for sertoli-spermatid cohesion
- essential for spermiation
what does testosterone bind to?
androgen binding proteins and then travels to and stimulates ducts
what is testosterone converted to in sertoli cells?
dihydrotestosterone and oestrogen
how long does passage through epididymis take?
5-11 days.
what happens to sperm in epididymis to mature them?
sperm acquired the potential to swim and fertilise oocytes- dependent on androgens.
where are mature sperm stored?
tail end of epidiymis
