PSL201Y1 Lecture Notes - Oocyte, Endocrine System, Betabaculovirus

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29 Nov 2011
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Hormonal control of Reproduction in Women
In the years before puberty, the female reproductive organs are
immature and incapable of generating ova. At the beginning of
puberty, the secretion of GnRH rises dramatically. The increase in
GnRH triggers a similar rise in gonadotropin levels. This in turn
stimulates the onset of gametogenesis as well as the productions of
estrogen and progesterone at the ovaries. In this way, hormone
production has driven the chromosomal events that make reproduction
possible.
The female is not only responsible for the production and
transport of the ova but also for everything else that enables a new
human being to be born. Similarily to the male, in females,
gametogenesis and hormone production are performed by the gonads,
or the ovaries.
Gametogenesis
Gametogenesis in the female is called oogenesis. After puberty,
once every month, the ovaries deliver an early ovum the the uterine or
fallopian tube. The end of the tube near the ovaries are trumpet
shaped and has featherly projections called fimbria. It is the fimbria
that act to catch the early stage ova that exit the ovary once a month
on their trip to the uterus. The uterus has muscular walls for
contractions which help push the fetus out of the cervix during birth.
The other function of the ovaries is hormone production. As in the
male, specialized cells of the female gonads secrete various hormones
in response to the anterior pituitary hormones, the gonadotropins.
After puberty, the uterus and ovaries got hrough cyclic changes in
activity every month in conjunction with varying levels of the
gonadotropins and ovarian hormones.
Causes of infertility
In females, the most common causes of infertility include those
due to mechanical issues such as scar tissue that causes blockage of
the uterine tube. Blockage of the uterine tubes usually occurs as a
result of a previous infection or endometriosis.
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A common area of injury is the distal end of the tube or the
delicate fibria. Injury can be severe enough to result in complete
closure of the tube. The uterine tubes normally produce a watery
secretion which can build up behind these blockages. When one or
both uterine tubes are blocked, the spermatozoa count meet the
ovulated ovum and therefore fertilization cannot occur. Endometriosis
is another common cause for infertility. It can also be associated with
obstruction of the uterine tubes. It refers to a topic or misplaced
uterine tissue.
Another case of fertility is due to problems with ovulation. This
may be complete ovarian failure due to problems with levels of
hormones or receptor. It can also be a problem of timing or detection
of ovulation.
Ovaries and reproductive tract
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The inner layer of the uterus in called endometrium and the
muscular layer is the myometrium. The endometrial layer is highly
granular and goes through substancial morphological changes in
response to varying levels of pituitary and ovarian hormones
throughout the mestrual cycle. The fimbriae encircle the ovary on
either side of the uterus. Each ovary is composed of dense connective
tissue but embedded in it are numerous spherical structures called
follicles. Each follicle contains one developing ovocyte, an early stage
ovum.
The system exhibits these general characteristics that do not
apply to men:
1. Displays yclic changes in activity
2. Displays restricted periods of fertility
3. Displays limited gamete production
Oogenesis
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