Gametogenesis Flashcards
define gametogenesis?
the process in which cells undergo meiosis to form gametes.
what determines the sex of the zygote? how many chromosomes do we have?
which sperm fuses w/ the ovum to form the zygote
- es: sperm containing y chromosome> boy*
- or sperm containing X >girl*
what r primodial germ cells? function?
developing gonads r colonised by primodial germ cells!
first recognized in the developing embryo in the WALL of the yolk sac! near the allintois.
the migrate through the developing embryo, migrating towards the gonadoridges.
depends on the type of primordial germ cells which colonize the gonads>> that will determine the sex
once they colonised the gonad, they proliferate via mitosis
then undergo meiosis!
difference btw spermatogenesis and oogenesis
feMale only has 400 chances to reproduce
while male nafs confetti, ishkithirr
where does spermatogenesis take place?
lumen of semineforus tubules
occuring in btw the gaps of these sertoli cells!
why r tight junctions formed by sertoli cells in the testes important? (2)
- they seperate the 2 compartments of the testes > Basal compartment & Adluminal .
- forms blood testis barrier > the gametes can be recognized as non-self by the males! prevents the membrane antigens of differtiating sperms from escaping into the BS where they would activate an immune response!
what r the 2 compartments of the testis?
why is it important that theu r sepertated by tight junctions?
Basal> spermatogonium or germ cells reside (in contact w/ blood)
Adluminal>
the cellular environmet and conditions to maintain our stock of germ cells r different than the cellular conditions that r needed for the differentiation of spermatids into sperm
Vasectomy risks
The blood–testes barrier can be damaged by trauma to the testes (including torsion or impact), or surgery or vasectomy.
When the blood–testes barrier is breached, and sperm enters the bloodstream, the immune system mounts an autoimmune response against the sperm,
functions of leydig cells?
makes testosterone which help to signal spermatogenesis to occur
when do these processes take place?
occur in male AFTER puberty has occured,
up until puberty we have our spermatogonium in a DORMANT stage (just chilling ya know)
difference btw spermatogenesis & spermiogenesis
spermatogenesis: is the process where we produce spermatozoa from spermatogonial stem cells by mitosis and meiosis
spermiogenesis: is the final stage of spermatogenesis, which sees the maturation of spermatids into mature, motile spermatozoa
name the raw material’ for spermatogenesis
Spermatogonia
2 types of spermatogonium?
Ad spermatogonium (“Resting”: reserve stock) not really doing much
Ap spermatogonium (“Active”: renew the stock of germ cells or go through mitosis to maintain the stock)
- Ad for dark (sitting in a dark place)*
- Ap for pale*
which types of spermatogonium go on to form gametes?
Type B spermatogonium
Following mitosis, the tight junctions of sertoli cells open to allow type B cell to pass into adluminal compartment
(like locks in canal that open to allow boats to pass!)
explain the stages of spermatogenesis
Distinguish spermatogenic cycle and wave
what is spermiogenesis
Each spermatid has the correct chromosomal # for fertilization… but is NONMOTILE
it still needs to undergo a process called spermiogenesis! during which it elongates, sheds it cytoplasmic baggage & forms a tail! on its way down to the lumen
transformation of a spermatid into a functional sperm
spermiation
Spermatids released into lumen of seminiferous tubules
when do sperms gain their motility?
once theyre in the epididymis!
if sperms gain their motility in the epididymis, then how did they even get their in the first place? (2)
via sertoli cells secretions & peristaltic contractions!
(sertoli secretion: testicular fluid pushes them)
which structure on the sperm gives it its motility?
Flagellum
which structure on the sperm is important in order to allow the sperm to penetrate the zona pellucida layer on the oocyte?
the Acrosome! (helmet)
it contain hydrolytic enzymes that form digestive holes on the zona pellucida!
the sperm has to travel along journey, where does it get its energy from
Mitochnodria provide energy (ATP) needed for whiplike movemnts of the flagellum tail
what r different types semen secretions and where do they occur
which one has the most %?
motility of the sperm is related to what ion?
ZINC
function of bulbourethral gland secretions,
another name for this gland is?
Also called Cowper gland.
what is the final process the sperm goes through so it can finally become fertile!?
Sperm capacitation!
removal of its helmet when its in the females
this Allows perm to bind to zona pellucida of oocyte and initiate acrosome reaction
what activates sperm capacitation? what is being removed from its membrane?
Conditions in female genital tract stimulate it!
Removal of glycoproteins and cholesterol from sperm membrane
when does maturation of oocytes occur?
b4 birth
the female developed her entire stock of potential gametes BEFORE BIRTH!
describe oogenesis, starting from the oogonium
they ARREST at Mieosis 1
they dont actually complete it YET,
these cells r called primary oocyte
difference btw oogonium and primary oocyte?
when do u acheive ur Max # of germ cells?
Max number germ cells reached by mid gestation
when the max # of germ cells has been completed, what happens after
Cell death then begins and many oogonia and oocytes degenerate (atresia)
By 7th month gestation majority of oogonia have degenerated, what do the ones alive do now?
primary oocytes have now entered meiosis 1 (but still arrested in prophase 1) & r individually surrounded by layer of flat epithelial cells called follicular cells >>
now called primordial follicule!
when does meiosis 1 continue in women?
after they have reached puberty, and will be COMPLETED when the ovum has been fertilized!
cells will continue meisos 2 when they have been fertilized by a sperm.
ya3ny 3ady yg3doon 40 or more yrs imba96een maku sh3’l.
the cell has been in that arrested state for 40 or more yrs.
this explains why there could be many defects later on with late preganncies
the older the women is when pregnant, the higher the chance of chromosomal abnormalites
okay so by the time these oocytes reaches puberty 15-20 oocytes start to mature each month! passing through 3 stages: describe em
- Preantral
- Antral
- Preovulatory
what happens in preantral stage?
Antral stage
Preovulatory stage
what causes ovulation to occur
LH SURGE!!
- increases collagenase activity
- theca cells produce proteolytic enzymes
- local muscular wall contractio in ovarian wall
>>>OOCYTE LEAVES AND BREAKS FROM OVARY!
what happens to the theca and granulosa cells that the ooyte left behind in the ovaries?
how is the oocyte transported out of the ovaries?
& if fertilized, how many days dos it reach the lumen?
what happens to the Corpus Leuteum,
- If fertilization occured,
- if it did not occur?
which day does ovulation occur?
what hormones peak?
14 day!
LH, FSH
ovarian cycle sequence of events graph!
describe the phases of the menstrual cycle!
and hormones involved in each phase
compare oogensis and spermatogenesis
- products
- when it starts
- ends?
- how many per day produced
product of oogenesis
mature oocyte and 3 polar bodies
Which term describes the distance between cells at the same stage of spermatogenesis down the length of the seminiferous tubule?
The spermatogenic wave. Note: The Spermatogenic cycle is different from the spermatogenic wave and is defined as time taken for reappearance of the same stage within a given segment of tubule (~16 days in human).
Name the 2 daughter cells produced by meiosis 1 in oogenesis.
The secondary oocyte and the first polar body (both of which are haploid with 23 chromosomes and 46 chromatids)
What is the lifespan of the corpus luteum?.
14 days
when does crossing over occur in meiosis?
Prophase 1
how do u get genetic variation?
- crossing over
- independent assortment
- Random segregation
