Gametogenisis Flashcards
what is gametogensis
the process where specialsied cells, or gametes are produced. occurs in the gonads, for sexual reproduction.
gemetogensis in females
oogenesis
what are gonads
glands that produce hormones involved in reproduction.
testes - in males
ovaries - in females.
gemetogensis in males
Spermatogenesis
components of the testes
includes the twisted and coiled - seminiferous tubules, where sperm is made and the epididymis, where the sperm further matures (longer flagella and more mitochondria), and get ready for ejaculation.
what are the components of the seminiferous tubules
has a smooth muscle layer - to help propel the sperm from the tubules into the epididymis.
and many sertoli cells,
what is the process, of movements of the sperm from tubules into the epididymis.
like squeezing toothpaste from bottle.
peristalis. l=wave like muscle contraction.
where is the sperm made in the seminiferous tubules
in between 2 sertoli cells.
what is the precursor of the sperm cell, or the intial cell where all the sperm comes from.
the Spermatogonium, they are the undifferentiated germ cells in the testes.
where is the tight junction found, and what is its function
found near the far ends of the sertoli cells, which seperates the basal compartment (outside area of the tubules) and the lumenal compartments.
- it opens up to let the primary spermocytes through, and closes up immediately, to prevent leakege and maintain optimum environments.
what is the primary spermocyte formed from, and how.
how many chromoseoms does it have.
formed from the intial spermatogonium. formed by mitosis and then differentiation.
A diploid cell with 46 chromosomes.
what 2 cells does the mitosis of spermatogonium, result in.
1 cell undergoes differentiation, to form the priamry spermatocyte, and the other cell essentially reverts back to reform another spermatogonium.
the (diploid) primary spermocyte’s cytoplasm grows in size, what happens after.
the primary spermocyte undergoes corssing over in prophase 1, and then
dividies into 2 secondary spermocytes, by meiosis 1.
now the secondary spermocytes are haploid cells with 23 chromosomes, still with 2 sister chromatids.
what do the secondary spermocytes divide into,
how many chromosomes, do the products have
each secondary spermocytes, divides into 2 spermatids each, during meiosis 2. here the sister chromatids have seperated.
results in each spermatid being a haploid - having 23 chromosomes, and one sister chromatid each.
How is the spermatozoa formed.
spermatids are differentiated into spermatozoa, through the process of speriogenesis.
where does further maturation (spermoiogenesis) of the formed spermatozoa occur and what is included.
At the border of them lumen,
- the removal of excess cytoplasm and organelles including ribosomes and endoplasmic reticulum.
- Forming a streamlined, motile cell
- further condensation of chromatin.
- acrosome matures from the golgi complex, acrosin enzymes and other polysaccharides.
all allowing them to become functional cells.
how long does maturation of the spermatozoa take
usually 2-3 weeks.
how many spermatozoa are formed by a single diploid spermatogonium
4
when does spermatogenesis occur in males
at around ages 10-14, when puberty starts
describe a timeline of how spermatogenesis starts from fetal developments until puberty.
fetal development = spermatogenia under mitosis, increasing in number.
start of puberty (10-14 years) - meiosis starts.
- under the influence of hormonal changes, differentiation occurs and other processes result in spermatozoa forming.
what does the head of a sperm cell consist of
the nucleus, cell membrane and acrosome cap.
describe the acrosome cap -
- how it is formed
- structure
- function
made from the goli complex during spermiogenesis.
consists of the acrosin enzyme, and other polysaccharides.
- has its own acrosomal membrane.
- involved in the recognition of te oocyte based on it’smolecule composition = chemotaxis,
describe the midpiece -
main characterisitic of it.
contains tightly packed mitochondira = energy for swimming and apoptosis.
where is the centriole found in a sperm cell.
main function?
between the head and the midpiece, refrerred to as the centrole-centrosome complex.
essential for movement, and production of mitotic apparatus for seperating chromsomes, whilst being a template for all subsequent centrioles.
what % does the tail make up of the sperm cell
about 80%
what is the main germ cell that starts oogenesis
the oogenium
what happens to the oogonium first, in oogenesis
it undergoes mitosis, increasing no. of cells, forming the primary oocyte. (upto 1-2 mill).
what cell division phase are primary oocytes arrested in
prophase 1.
where does the mitosis of the ooogonium to form primary oocyte occur
in the utero - before birth. (the womb).
when does the primary oocyte leave the prophase 1 arrest, and what happens after.
leaves after puberty, undergoes meiosis 1, to form the secondary oocyte with 23 chromosomes (1n) and the 1st polar body.
how are polar bodies formed and what are they
they are formed, by unequal division of a cell, the (primary and secondary) oocyte being the larger and more important of the two. the polar body has less of the cytoplasm, but equal chromosomal content.
- later dies.
what meiotic phase is the secondary oocyte arrested at
metaphase 2.
what triggers the meiotic division of the primary oocyte into the secondary oocyte.
at adolescence, the aterior pituirty hormones cause the development of many follicles in the ovary. which finishes the first meiotic division = secondary oocyte
what happens to the seoncdary oocyte during ovulation, (if no sperm enters)
the secondary oocyte travels through the fallopian tubes, on its way to the uterus, without every finishing meiosis 2.
- gets disingrated there and later any remaining material will be shed from the body in the next period.
where does the sperm meet the egg cell. for fertilisation to occur.
the sperm travels from the uterus into the fallopian tubes where fertilisation with the ovum occurs.
when is the egg oficially called the ovum in oogenesis
called the ovum, only after the egg has been fertilised.
what processes happen for the second oocyte to become the ovum, and another polar body.
meiosis 2 continues and obvs fertilisation.
what does the genetic makeup of the fertilised egg consist of
a diploid cell with -
23 chromosomes from the father and 23 chromosomes from the mother.
what happens during ovulation
the secondary oocyte is released into the uterus (still in metaphase 2) through the oviduct.
in what process does the sperm and egg cell nuclei fuse
during syngamy, which occurs after the sperm penetrates the egg, during fertilisation.
when does ovum become a zygote
after fertilisation
what is the difference in terms of of number of gametes produced during oogeneis and spermatogenesis
spermatogenesis = 4 functional sperm cells from 1 speratogonium
oogenesis = 1 egg and 2 polar bodies from each oocyte.
