Reproductive System and
Developement
By Bryce Tappan
Function of the Reproductive System
The reproductive system has several vital functions,
and they differ a bit from male to female. The
shared functions are that both male and female
reproductive systems make gametes and
hormones. Also, the reproductive system
provides a means for the male gamete (sperm) to
travel to the female egg. Within the female, the
reproductive system functions to help the zygote
develop.
http://www.livestrong.com/article/37137-reproductive-system-functions/
Sexual vs. Asexual
Asexual reproduction means that an organism
can proliferate without intercourse between
cells of different genders. Normal cells grow
in this fashion; they require no input from
outside cells, and the offspring are essentially
clones. Sexual reproduction occurs when one
gamete, the male cell, fertilizes another
gamete, the female cell, forming a zygote.
http://www.biotopics.co.uk/genes1/asexual_and_sexual_reproduction
.html
Examples of Asexual Reproduction
Many plants produce asexually:
Chlorophytum makes “plantlets” that are
genetically identical to the parent plant and will
grow up to be almost identical.
Bacteria- most bacteria reproduce asexually from a
process called binary fission.
Liverworts, a bryophyte, produces asexually
http://www.biotopics.co.uk/genes1/asexual_and_sexual_reproduction
.html
http://en.wikipedia.org/wiki/Marchantiophyta
Spermatogenesis
Spermatogenesis is the process in which haploid
sperm cells are created in the testes, and it can
be divided into three stages. The first stage,
spermatocytogenesis, begins in the seminiferous
tubule within the testes. Initially, these cells
divide through mitosis, but after a certain
number of cells exist they divide meiotically,
creating haploid cells called secondary
spermatocytes. They then divide again to create
spermatids which go dormant and mature into
spermatozoa.
http://www.rci.rutgers.edu/~uzwiak/HumanSexuality/HSSpringLect3.html
Oogenesis
Oogenesis occurs within the follicles of the ovaries.
Oogenesis is the creation of a female sex cell, an
egg, that is also a haploid cell created from an
original diploid cell called a oocyte. Each oocyte
divides meiotically and leads to the production of
a single egg and three polar bodies. The fact that
the egg and the sperm are both haploid cells
allow for fertilization to create a diploid zygote
with genetic variation from its parents.
http://www.sparknotes.com/testprep/books/sat2/biology/chapter7section2.r
html
Unequal Division of cytoplasm in
oogenesis
When an oocyte goes through meiosis, a large
haploid oocyte and a smaller polar body are
created. The second division is once again
unbalanced, creating a large ootid and an
even smaller polar body. The unequal division
is an advantage because it gives the one egg a
large amount of cytoplasm and little to the
nonfunctional polar bodies.
http://www.madsci.org/posts/archives/2004-05/1084815953.Dv.r.html
Menstrual Cycle
The menstrual cycle occurs to prepare females for the
possibility of reproduction in three main stages:
the follicular phase, ovulation, and the luteal phase.
About once a month, the uterus grows a new
endometrium (lining) to get ready for a fertilized egg.
If no fertilization occurs, then the uterus disposes of
the lining through menstrual bleeding. The menstrual
cycle is regulated by hormones such as estrogen and
progesterone. Build up of hormones prepare the uterus
for pregnancy, and a drop in hormones triggers
periods.
http://women.webmd.com/tc/normal-menstrual-cycle-topic-overview
Estrous Cycle
Both the estrous cycle and the menstrual cycle
are regulated by hormones, however there
exist differences between the two cycles as
well. The estrous cycle is different from the
menstrual cycle in that the endometrium is
absorbed at rather than shed as it is in the
menstrual cycle.
Estrous Cycle vs Menstrual Cycle.doc - Strathmore High School
Hormonal Control
Luteinizing hormone and follicle-stimulating
hormone, both produced in the pituitary gland,
facilitate the ovaries to begin ovulation. The
ovaries then produces estrogen and
progesterone, which trigger the uterus to
become ready for a possible fertilization. When
levels of these hormones decrease, the lining of
the uterus breaks down and begins to shed.
http://www.merckmanuals.com/home/womens_health_issues/biology_of
_the_female_reproductive_system/menstrual_cycle.html
Feedback Mechanism
The release of many hormones are controlled by
what is called a negative feedback mechanism.
For example, in the menstrual cycle, the pituitary
gland releases hormones to trigger certain
events. When the body senses that there is
enough, or an excess, of hormones to perform a
duty, the gland that excretes those hormones is
temporarily turned off. A negative feedback
system is one that produces something that
eventually triggers the shutdown of the producer.
http://www.hormone.org/Endo101/page3.cfm
Cleavage
In multicellular organisms, cleavage is the first
step of development. The single celled zygote
divides mitotically to produce a blastula. The
proliferation of cells allows for a decrease in
the size of each cell, but still increases the
surface area to volume ratio, which gives the
blastula access to more oxygen and resources.
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookr
eprod.html#Fertilization%20and%20Cleavage
Cleavage
•
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookreprod.html#Fertilization%20
and%20Cleavage
Gastrulation
Gastrulation is the process in which the blastula changes
shape to form three layers of cells: the ectoderm, the
mesoderm, and the endoderm. The ectoderm leads to
the formation of the skin, hair, CNS, sweat glands, and
epithelium. The mesoderm creates muscles, bones,
cartilage, blood, the reproductive organs and kidneys.
The endoderm forms respiratory and digestive organs,
many glands, the endocrine system, liver, pancreas,
and gall bladder.
http://www.emc.maricopa.edu/faculty/farabee/biobk/bi
obookreprod.html#Fertilization%20and%20Cleavage
Organogenesis
Organogenesis is the process in which the
ectoderm, endoderm and mesoderm develop
into the body parts of a living creature. The
germ layers, listed above, each form different
parts of the body as follows in the next slide.
www.wikipedia.org
Germ layers develop into:
Ectoderm-forms the spine, peripheral nerves, brain,
skin, and the lining of mouth, anus, nostrils,
sweat glands, hair and nails
Endoderm- forms the gastrointestinal, urinary, and
respiratory tracts, the endocrine system, and the
auditory system
Mesoderm-forms muscles, connective tissues,
blood cells, the lining of coelums, and the
gonads.
www.wikipedia.org
Morula, Blastula, Gastrula
Once the zygote begins to divide, it forms a ball of out of cells called
blastomeres, and this ball is called a morula. Within the morula, a hollow
cavity forms.
Next in the development of the embryo is the blastula, which is a hollow ball
of cells formed from the morula.
Once the blastula has formed, the next step of development is the formation
of the gastrula. The blastula is arranged in a way so that the ball has three
layers of cells, called germ layers. These germ layers are the beginnings of
the development of the body of the organism, which include the
ectoderm, mesoderm, and endoderm.
http://en.wikipedia.org/wiki/Morula
http://en.wikipedia.org/wiki/Gastrula
http://en.wikipedia.org/wiki/Blastula
Reproductive System Disorders
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