Reproductive System and Development Douglas Todey
Apr 01, 2015
Reproductive System and Development
Douglas Todey
FunctionsThe reproductive system has four functions
To produce sperm and egg cellsTransportation and sustenance of cellsDevelopment and nurturing of offspringProduction of hormones
ReproductionSexual 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 ReproductionThis is when one organism breaks in half and each
half regrows as an exact replica of the originalExamples
Tapeworms Jellyfish Echinoderms
SpermatogenesisThe diploid germinal cells of the seminiferous
tubules produce the spermatidsMultiplication 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 PhaseThe 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 pro duce the sperms At the end of maturation phase, each germinal cell
would have produced four spermatids.
Spermatogenesis, Cont.
OogenesisMultiplication 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 PhaseThe primary oocyte increases in size considerablyThe 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 CyclesMenstrual 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 CycleThe 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 CycleThe menstrual cycle is a 28-32 day cycle found
in both humans and primatesThe ovarian cycle involves the ovulation of the
egg from the ovaries in which a woman then becomes fertile
Hormonal ControlWomen also make estrogen and progesterone hormonesThe 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 EmbryoThe 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 blastulaFrom the blastopore
Deuterostomes The mouth develops from the blastopore
Protostomes The anus develops from the blastopore
These blastopores are called the gastrula
Germ LayersGerm layers are the concentric layers that form
various tissues and organsEctoderm
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
InfertilityThis means that a person cannot have a childThe main symptom is the inability to become
pregnantApproximately 9% of women are infertileTreatment 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 CancerThis is cancer that is found in a woman’s
ovariesSymptoms 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/AsexualReproduction.html
http://www.preservearticles.com/2012042131003/short-notes-on-the-process-of-spermatogenesis.html
http://www.preservearticles.com/2012042131004/short-notes-on-the-process-of-oogenesis.html
http://www.uwyo.edu/wjm/repro/estrous.htm http://
www.womenshealth.gov/publications/our-publications/fact-sheet/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 /