Reproductive System and Development
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Transcript Reproductive System and Development
Douglas Todey
Functions
The reproductive system has four functions
To produce sperm and egg cells
Transportation and sustenance of cells
Development and nurturing of offspring
Production of hormones
Reproduction
Sexual Reproduction
Male and female sex cells, produced by meiosis so each
cell is genetically different providing for genetic
variation in the offspring, combine to create an offspring
Asexual Reproduction
This is when one organism breaks in half and each half
regrows as an exact replica of the original
Examples
Tapeworms
Jellyfish
Echinoderms
Spermatogenesis
The diploid germinal cells of the seminiferous tubules
produce the spermatids
Multiplication Phase
Germ cells increase their number by undergoing
repeated mitotic divisions.
As a result of this a large number of cells called sperm mother
cells are formed
Growth Phase
The formed cells absorb nutrition from the surrounding
cells of germinal epithelium and grow in size
These enlarged cells are called spermatocytes
Spermatogenesis, Cont.
Maturation Phase
The process of reduction division or meiosis will be
completed
The two haploid cells that are formed after meiosis I are
called secondary spermatocytes
The two secondary spermatocytes undergo meiosis II to
produce four cells which are called spermatids
The spermatids do not undergo any further division but
simply undergo metamorphosis to produce the sperms
At the end of maturation phase, each germinal cell would
have produced four spermatids.
Spermatogenesis, Cont.
Oogenesis
Multiplication Phase
The primordial germ cells divide repeatedly by means of
mitosis to produce a large number of daughter cells, oogonia
They divide several mitotically to produce a large number of
primary oocytes
Growth Phase
The primary oocyte increases in size considerably
The cytoplasm of the oocyte is very rich in RNA, DNA, and
enzymes and other cytoplasmic organelles like mitochondria,
golgi complex and ribosomes are also found in large numbers
Oogenesis, Cont.
Maturation Phase
Oocyte undergoes meiosis to produce an egg or ovum
One large haploid egg is formed along with three small
polar bodies
The cytoplasm divides unevenly to provide the
maximum amount of nutrients for the developing
embryo
The polar bodies will eventually ooze out and degenerate
while the egg is ready for fertilization
Oogenesis, Cont.
Menstrual and Estrous Cycles
Menstrual Cycle
This is a 28-day cycle in women when the egg leaves the
ovary and is available to be fertilized
On day 14, ovulation occurs, which is when the egg
leaves the ovary
Estrous Cycle
The estrous cycle is the period when animals such as
dogs, cattle, or horses are considered “in heat” and
should be bred
Females will only allow males to mate during this period
to increase the chance of being bred
Menstrual Cycle
The menstrual cycle is a 28-32 day cycle found in both
humans and primates
The ovarian cycle involves the ovulation of the egg from
the ovaries in which a woman then becomes fertile
Hormonal Control
Women also make estrogen and progesterone hormones
The synthesis and secretion of estrogens is stimulated by
follicle-stimulating hormone (FSH), which is controlled by
the hypothalamic gonadotropin releasing hormone(GnRH)
Secretion of GnRH depends on neurons in the
hypothalamus which express a gene encoding a protein of
145 amino acids. From this, several short peptides are cut
collectively called kisspeptin. These are secreted and bind
to G-protein-coupled receptors on the surface of the GnRH
neurons stimulating them to release GnRH. However, high
levels of estrogen inhibit the secretion of kisspeptin and
suppress further production of those hormones
Development of the Embryo
The fertilized egg starts dividing in which the cleavage of the egg
determines whether it is a protostome or a deuterostome. This is
called the morula
Then the coelom forms in the
gastrulation stage. The cells push
inward and form a double layered
cell wall and the hole created is
called the blastopore. This group of
cells is called the blastula
From the blastopore
Deuterostomes
The mouth develops from the blastopore
Protostomes
The anus develops from the blastopore
These blastopores are called the gastrula
Germ Layers
Germ layers are the concentric layers that form various
tissues and organs
Ectoderm
Creates the outer covering of the animal
Can also make the central nervous
system
Endoderm
Creates the digestive tract
Also makes the liver and lungs
Mesoderm
This creates the muscles
It also makes most other organs between
the outer covering and the digestive tract
Infertility
This means that a person cannot have a child
The main symptom is the inability to become pregnant
Approximately 9% of women are infertile
Treatment includes education and counseling, fertility
treatments, medicines to treat infections and clotting
disorders, and medicines that help the woman grow
and release eggs from the ovaries
Ovarian Cancer
This is cancer that is found in a woman’s ovaries
Symptoms include bloating or swollen belly area,
difficulty eating or feeling full quickly, and pelvic or
lower abdominal pain
There will be approximately 22,280 new cases of
ovarian cancer in 2012 and 15,500 will die of it
Treatment includes surgery to remove the uterus, both
ovaries, or the fallopian tubes
Sources
http://www.livestrong.com/article/37137-reproductive-system-functions/
http://www.biotopics.co.uk/genes1/asexual_and_sexual_reproduction.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AsexualReproducti
on.html
http://www.preservearticles.com/2012042131003/short-notes-on-the-processof-spermatogenesis.html
http://www.preservearticles.com/2012042131004/short-notes-on-the-processof-oogenesis.html
http://www.uwyo.edu/wjm/repro/estrous.htm
http://www.womenshealth.gov/publications/our-publications/factsheet/menstruation.cfm
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/SexHormones.html
AP Biology Campbell and Reece textbook
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002173/
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001891/