gametogenesis Flashcards
when does meiosis occur in testicle-having individuals
during puberty and adulthood
what would happen to the production of sperm if we prevented mitosis from happening (but allowed meiosis to continue)
sperm production would continue normally, then halt
timeline of spermatogenesis and spermiogenesis
spermatogonium -> primary spermatocyte -> secondary spermatocyte -> spermatids -> sperm (spermatozoa)
secondary spermatocytes are
haploid
what is spermatogenesis
diploid cell becoming 4 haploid spermatids, physical maturation of spermatids into sperm
what direction do germ cells go to be mature sperm
cells migrate from basement membrane toward lumen of seminiferous tubule as they develop
why do we have an acrosomal cap
breaking through egg’s membrane, has enzymes to break through zona pellucida
why do we have many mitochondria around the neck
power and propulsion, ATP
why do we need to reduce cytoplasm
extra weight, drag
what is production rate of sperm
1000 per sec
what percentage of sperm in a sample are normal
5-15%
when does meiosis occur in ovary-having individuals
in the developing fetus, during puberty, in adulthood
how many gametes result from a single round of meiosis in ovary-having individuals
1
oogenesis
meiosis in ovary-having people arrests in 2 different time points:
-prophase I (at birth)
-metaphase II (at ovulation)
-completes after fertilization
oogenesis 2
oogonium –> primary oocyte –> secondary oocyte –> ovum –> fertilized egg (zygote)
a hormone moves through the plasma membrane and activates a receptor in the cytoplasm. this hormone is likely a
steroid
what are peptides
surface receptors
what are steroids
surface and intracellular receptors
what would happen to sperm production if there were a decrease in FSH levels
decrease
primary oocyte peak numbers
-peak # (~7 million) of primary oocytes occurs around 20 weeks gestation
-# at birth ~1 million
-arrested in prophase 1 until puberty
-# at onset of puberty ~200,000
-small # start ‘maturing’ each month to finish meiosis I
what do sertoli cells help with
secrete proteins to support sperm production
why does constant release of GnRH from the hypothalamus drop levels of LH and FSH
constant release of GnRH uncouples receptor from second messenger pathway and internalizes receptors
instead of constant release of GnRH, how does it need to be released
pulsatile generation via neurons called pulse generator of GnRH
what is the feedback loop for KISS neurons
-KISS neurons release KISS peptides which increase GnRH release
-negative feedback from sex steroids reduces KISS neuron excitability = less KISS peptide = less GnRH release
