gametogenesis Flashcards
(38 cards)
where does meiosis occur?
germ cells of the gonads
male vs. female meiosis
gives rise to 4 haploid cells in both
male all 4 gametes mature into spermatazoon
female 1 gamete - ovum - recieves almost all cytoplasm from mother cell - other 3 - polar bodies - degenerate
when do male spermatagonia proliiferate?
they’re present in small quantities before puberty, but undergo mitosis at puberty
when do oogonia proliferate?
during foetal development
production vs. development of male gamete
spermatogenesis + spermiogenesis
occur in medulla of testes - in seminiferous tubules
both processes take 64 days + are synchronised, so cross sections of seminiferous tubules look different at different parts
where does final maturation of spematozoa occur?
epididymis
process of spermatogenesis
- primordial germ cells migrate from yolk sac to indifferent gonad
- germ cells then migrate to medulla of testis
- undifferentiated diploid germ cells = spermatogonia A
- spermatagonia A undergo mitosis to produce more spermatogonia A - which maintain germ cell pool - and spermatagonia B - which undergo mitosis to produce primary spermatocytes
- primary spermatocytes undergo meiosis - process takes 3 weeks - daughter cells = secondary spermatocytes
- secondary spermatocytes undergo meiosis rapidly to becom spermatids - are rarely seen because of this
- spermatids undergo spermiogenesis to become spermatozoa
what are the endocrine cells in the testes relevant to spermatogenesis?
leydig cells - secrete testosterone - interstitial spaces between tubules
what cells support germ cells during spermatogenesis?
sertoli cells
- cytoplasmic barriers
- testis-blood barrier
- provide nutrients
- phagocytose
process of spermiogenesis
- acrosomal vesicle attaches to one pole of condensing nucleus of spermatid to form acrosomal head cap
- both centrioles migrate to opposite end of spermatid away from acrosome
- one centriole elongates to form the flagellum
- cytoplasm migrates to first part of flagellum - midpiece. - mitochondria thus gather in midpiece
- excess cytoplas is phagocytosed by surrouding sertoli cell
- spermatozoa is released into lumen - spermiation
spermiation
release of spermatozoa into lumen
maturation of spermatozoa
- in epididymis
- takes 1-21 days
- sperm gain fertilising capacity + high motility
passage of sperm
- seminiferous tubules
- tubuli recti
- rete testis
- efferent duct
- epididymis
- vas deferens
- urethra
santa told reese red turtles eat ducks every valentines day, understand?
glands which contribute to seminal fluid
seminal vesicles - 65%
prostate gland - 25%
bulbourethral gland - 10%
composition of ejaculate
- spermatazoa
- seminal plasma - comes from accessory glands - maintains PH - gives nutrients - transport medium
process of oogenesis
- primordial germ cells migrate from yolk sac to indifferent gonad
- migrate to cortex of ovary
- 4th month foetal development - oogania enlarge into primary oocytes
- primary oocytes begin firts meiotic division
- 7th month - layer of flalltened follicular cells surround oocyte - form primordial follicles = oocyte + follicle cells
- envelopment arrests meiosis until puberty
- at puberty folliculogenesis begins
degredation of female germ cells
atresia - can occur at any point of folliculogenesis
folliculogenesis stimulated by ____
FSH - follicle stimulating hormone
process of folliculogenesis
- primordial follicle enlarges to primary follicle - bigger oocyte + more follicular cells
- follicular cells now called granulosa cells
- follicular cells + oocyte secrete proteoglycans + glycoproteins - form thick homogenous layer called zona pellucida between granulosa + oocyte
- surrounding stromal cells form organised layer around follicle called theca folliculi
- granulosa proliferate to form several layers - zona granulosa
- fluid filled spaces develop between granulosa cells + coalesce to form follicular antrum
- now a secondary follicle
- in the secondary follicle primary oocyte is in thickened layer of granulosa called the cumulus oophorus
- theca folliculi has developed 2 layers - theca interna - round cells - theca externa - spindle cells
- first meiotic division completed just before ovulation - oocyte now secondary oocyte + follicle = GRAAF follicle
- cumulus oophorus diminishes - secondary oocyte surrounded by corona radiata now
- corona radiata attached to granulosa by thin bridges that break just before ovulation to leave oocyte floating freely
granulosa cells
what follicular cells becom after primordial follicle enlarges to primary follicle
- secrete glycoproteins + proteoglycans which form zona pellucida
stromal cells
connective tissue cells eg. fibroblasts which support perinchymal cells
theca folliculi
layer of stromal cells that surround primary follicle
follicular antrum
big fluid filled bubble in zona granulosa of SECONDARY follicle - develops when fluid filled spaces between granulosa cells coalesce
- changes primary follicle to secondary follicle
cumulus oophorus
thickened layer of granulosa in secondary follicle in which primary oocyte sits
