gonads Flashcards
the gonads: explain the stages of gametogenesis in male and female gonads; recall the principle structures of the testes and ovaries and their function
what do gonads develop as in males
testes
in males, what gene influences development of testes
SRY gene
what do gonads develop as in females
ovaries
2 functions of gonads
production of gametes for reproduction (gametogenesis); production of steroid hormones (steroidogenesis)
name of gametogenesis in males
spermatogenesis
name of gametogenesis in females
oogenesis
activation of spermatogonia: when and duration
very high before birth and maintains high levels throughout life as differentiation and self-renewal; begins at puberty
activation of oogonia: when and duration
very high before birth; rapid atresia of many primordial follicles before birth; continued atresia through puberty until menopause, when no more cells activated
name of degeneration of ovarian follicles which do not ovulate
atresia
what hormone “rescues” follicles from atresia
FSH
how many oocytes are present at 24 weeks of gestation
maximum of 6 million
how many oocytes will mature and reach ovulation
300-400
stages of spermatogenesis and number and sex of chromosomes
germ cell → spermatogonia → primary spermatocytes (all 44+XY; diploid) → (1st meiotic division) secondary spermatocytes (2nd meiotic division) → spermatids → spermatozoa (all 22X or 22Y; haploid)
stages of oogenesis and number and sex of chromosomes
germ cell → oogonia → primary oocytes (all 44XX; diploid) → (1st meiotic division) secondary oocytes (+ 1st polar body; 2nd meiotic division) → ovum (22X (+22X); haploid; + 2nd polar body)
what is a polar body
the other oocyte which doesn’t contain cytoplasm so eventually dies
anatomy of testes: where do testes develop
develop in abdomen
anatomy of testes: where do testes descend into before birth
descend into scrotum (lower than core temperature)
anatomy of testes: what does puberty cause an increase in
testosterone secretion
anatomy of testes: where does spermatogenesis occur
coiled seminiferous tubules
anatomy of testes: where are spermatozoa collected
rete testis
anatomy of testes: what are spermatozoa drained via
vasa efferentia
anatomy of testes: where are spermatozoa then stored
epididymis
anatomy of testes: what are spermatozoa expelled by to the urethra
vas deferens (surrounded by smooth muscle)
cross section of seminiferous tubule
across basement membrane: spermatogonia, leydig cells outside
what cells are inside spermatogonia
Sertoli cells
function of Sertoli cells
form seminiferous tubules; act as blood-testes barrier so large molecules in blood can’t enter; spermatocytes cross into and are enclosed inside Sertoli cells where they mature
what hormonal receptors do Sertoli cells contain
FSH and androgen receptors
in response to FSH what do Sertoli cells produce
inhibin and other molecules
what is inhibin intimately associated with
developing spermatocytes
function of Leydig cells
synthesise LH receptors, and in reponse to LH are principle source of testicular androgens, mainly testosterone
why is a close connection between Leydig cells and the seminiferous tubules necessary
spermatogenesis won’t take place without raised level of androgen
anatomy of ovaries
Graafian follicles surrounded by follicular fluid; granulosa cells then thecal cells; ovarian stroma
what is a Graafian follicle
max size oocyte as most sensitive to FSH
what does the Graafian follicle convert to upon ovulation
corpus luteum
