The formation of sperm is called...
spermatogenesis
the formation of eggs is called...
oogenesis
mitosis conserves __________, for each cell undergoing mitosis ____ daughter cells are formed
the number of chromosomes; 2
meiosis ____ the chromosome number, for each cell undergoing meiosis ____ daughter cells are formed
halves; 4
meiosis I is called ____________ and the daughter cells have 23 __________ chromosomes
reduction division; duplicated
meiosis II is called ____________ and the daughter cells have 23 __________ chromosomes
equational division' unduplicated
the number of chromosomes is reduced to 23 in which, meiosis I or meiosis II?
Meiosis I
the chromosomes go from being duplicated to unduplicated in which, meiosis I or meiosis II?
Meiosis II
spermatogenesis takes ______ days
64-72 days
where does spermatogenesis take place?
seminiferous tubules of testes
how many sperm are produced per day?
about 400 million
1000-2000 _______ migrate from embryonic yolk sac to embryonic testes
spermatogonia
spermatogonia divide slowly by _____ up until puberty
mitosis
spermatogonium have ____ chromosomes
46
at puberty, spermatogonium either become ______ or ______
spermatogonium A or spermatogonium B
what happens to spermatogonium A?
they remain on the outer wall of the seminiferous tubules, they are the furthest from the lumen and continue dividing my mitosis
what happens to spermatogonium B?
they pull inward towards the lumen
which are closer to the lumen of the seminiferous tubules, spermatogonium A or B?
B
which undergo mitosis, spermatogonium A or B?
A
Primary spermatocytes are closer or farther from the lumen that spermatogonium B?
closer
how many chromosomes do spermatogonium A & B have?
they both have 46
what does spermatogonium B turn into and when?
turns into a primary spermatocyte when it enlarges
spermatogonium B enlarges to become _____
primary spermatocyte
the first phase in a sperm's development is ______
spermatogonium
primary spermatocytes divide by ________ to form ________
meiosis I; secondary spermatocytes
secondary spermatocytes stay _______ to each other by a ________
attached; cytoplasmic bridge
secondary spermatocytes are closer or farther from the lumen than primary spermatocytes?
closer
since secondary spermatocytes are formed by meiosis I, how many chromosomes are in human secondary spermatocytes?
23
since secondary spermatocytes are formed by meiosis I, are the chromosomes in human secondary spermatocytes duplicated or unduplicated?
duplicated
secondary spermatocytes divide by ________ to form ______
meiosis II; spermatids
spermatids stay _______ to each other
attached
secondary spermatocytes are closer or farther from the lumen than spermatids?
farther
spermatids matures into _____ by a process called ______
spermatozoa; spermiogenesis
1 spermatogonium will produce _____ spermatozoa?
4
since spermatids are formed by meiosis, how many chromosomes are in human spermatids?
23
since spermatids are formed by meiosis, are the chromosomes in human spermatids duplicated or unduplicated?
unduplicated
what happens to sperm in spermiogenesis?
the get rid of their extra cytoplasm and start growing a tail
spermatozoa loose their excess ______
cytoplasm
_____ push inward toward lumen and are released into lumen
spermatozoa
since spermiogenesis is a maturation process instead of a divisional process, how many chromosomes are in human spermatozoa?
23
since spermiogenesis is a maturation process instead of a divisional process, are the spermatozoa duplicated or unduplicated?
unduplicated
are spermatozoa attached or not attached to each other?
not attached
are spermatozoa mature? can they fertilize an egg?
not mature yet, cannot fertilize an egg
where do the spermatozoa mature?
epididymis
the ______ cells protect and nourish sperm
sertoli cells; sustentacular cells; sustentacular cells of sertoli
what are "nurse cells" referring to?
sertoli cells; sustentacular cells; sustentacular cells of sertoli
for each primary spermatocyte you start with how many spermatozoa are formed after meiosis is complete?
4
when is oogenesis not complete?
when there is no fertilization
where does oogensis occur?
ovaries
when does mitosis of oogonia stop?
5th month of gestation
how many oogonia are produced?
6-7 million
toward the end of gestation, oogonia enlarge to become _____
primary oocytes
oogonia migrate from _______ to ______
embryonic yolk sac; embryonic ovaries
oogonia have _____ chromosomes
46
oogonia divide by ______ in the fetus
mitosis
oogonium turn into 2 _____ in which one turns into a ______
oogonia; primary oocyte
oogenesis begins in meiosis I or II?
meiosis I
primary oocytes are arrested in _______ phase
prophase I
at birth a female has about _____ oocytes left
2 million
at puberty a female has about _____ oocytes left
400,000
primary oocytes are formed when oogonia ______
enlarge
from puberty until menopause, under the influence of sex hormones, a few primary oocytes begin to ______
complete meiosis I
usually _____ oocyte(s) succeeds in completing meiosis I
only one
if more than one oocyte succeeds at completing meiosis I and if fertilization takes place _______ results
fraternal twins
when primary oocytes complete meiosis I, why is there an uneven division of cytoplasm?
because the secondary oocyte needs more nutrients to make the long journey to the uterus, the first polar body needs none (no journey)
when a primary oocyte is finished with meiosis one, what results?
one secondary oocyte and the first polar body
secondary oocytes begin meiosis II and become arrested in ______
metaphase II
what is ovulated?
a secondary oocyte, arrested in metaphase II
when a secondary oocyte is fertilized, what phase is it in?
metaphase II
if fertilization does not occur, what happens to the secondary oocyte?
it dies along with the first polar body
if fertilization does occur, the first polar body either ______ or ______
dies or divides to form 2 secondary polar bodies
if fertilization does occur, secondary oocytes complete _______
meiosis II
if fertilization does occur, what happens to the secondary polar bodies?
they die
in ovum, male and female nuclei combine to form ______ with ______ chromosomes
zygote; 46
the zygote divides by _______
mitosis
for each primary oocyte that starts meiosis, at best ______ ovum is formed (and that is only if fertilization takes place)
only 1
uneven division of cytoplasm during both phases of meiosis ensure that the fertilized egg _____
has nutrients on it's 7 day journey to the uterus
if the secondary oocyte become fertilized, it becomes an _____
ovum
an ovum is only formed if ______ takes place
fertilization