95. 96. spermatogenesis/ oogenesis Flashcards
oogenesis where do primordial cells go in a genetic female
cortex of gonad
divides by mitosis + increasex in number
after oogonia undergo mitosis, some degenerate.
what happens to the remining cells
primary oocytes undergo meiosis 1
primary oocytes/primordial follicle get arrested at prophase in meiosis 1
this is called DIPLOTENE STAGE
first meiotic division is not reached until puberty
how does a primordial follicle turn into a primary follicle
flat follicular cells become cuboidal then produces a stratified epithelium of granuosa cells.
granulosa cells and oocyte secrete glycoproteins = forms zona pellicuda
what is theca externa and interna
layers of follicles that secrete hormones important for yellow body development (corpus luteium)
in the secondary follicle what is the fluid filled cavity called
Antrum: it enlarges as it develops
what surrounds the secondary follicle
Granulosa cells where the oocyte is on form the cumulus oophorus
surrounding the oocyte = corona radiata
what happens to the follicles as tey develop
only 1 fully matures, the others degenerate and become atretic
what is the largest ovarian follicale and its size
25mm - mature (grafian) follicle
Just before ovulation, what happens to the primary oocyte in the graafian follicle
surge in Luteinizing hormone causes the oocyte to complete meiosis 1 and enter meiosis II
secondary oocyte forms and first polar body (meiosis I): oocyte gets all cytoplasm polar body none
secondary oocyte gets arrested at metaphase meiosis II
stays there until it is fertilized
if fertilization occurs, secondary oocyte completes meiosis II and becomes mature oocyte (gamete) and secondary polar body formed
what is controls the growth of the ovarian follicles
FSH
steps of spermatogenesis
spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, spermatozoa
what is the process called when spermatids turn into spermatozoa
spermiogenesis
where does spermatogenesis occur
seminiferous tubules of the testis
PGCs give rise to spermatagonial stem cells
what is the process duration from a spermatagonia to mature spermatazoon
74 days
what are the peculiarities of spermatogenesis
maturation begins at puberty
2 meiotic divisions without interphase stage
4 mature spermatozoa formed from 1 spermatogonia
What are Sertoli cells
derived from surface epithelium of testes
has occluding junctions- creates blood testis barrier
support and protection of developing spermatazoa
phagocytosis of resisdual bodies
What are Leydig cells
found in between seminiferous tubules
polygonal cells with lipid droplets
steroid secreting cells eg testosterone
spermatogenesis is regulated by what hormone
what does it cause
LH-luteinizing hormone from pituitary gland
it binds to receptors on Leydig cells which produce testosterone
testosterone binds to Sertoli cells to promote spermatogenesis
FSH also binds to Sertoli cells and produces testicular fluid
what does spermatogonial stem cells turn into and how
Type A spermatigonia which divides by MITOSIS to form clones
Then Type B wich dvdes to form primary spermatocytes
how does primary spermatocytes turn to secondary spermatocytes
prolonged prophase (dont hv interphase) then completes MEIOSIS l.
how does it become spermatids after secondary spermatocytes
undergoes meiosis ll
haploid 23 chromasomes
what occurs in spermiogenesis
- Golgi Phase: proacrosomal phase
- acrosomal phase: formation of acrosome which contain enzymes to penetrate the egg + condensed nucleus.
- maturation phase: formation of neck, middle piece , tail.+ shedding of cytoplasm into residual bodies
Spermiation: mature spermatozoa released form Sertoli cells to seminiferous tubules. in epididymis they gain full motility
how is spermiogenesis regulated
GRH - hypothslmus
FSH
LH
regulating factors: temperature, alcohol malnutrition, x rays
Abnormal gametes
more commmon in spermatozoa (10%) - giants, dwarfs, abnormal heads/tails. lacks motility
