The Female Reproductive System

The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for reproduction, called the ova or oocytes. The system is designed to transport the ova to the site of fertilization. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. After conception, the uterus offers a safe and favorable environment for a baby to develop before it is time for it to make its way into the outside world. If fertilization does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining). In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.

During menopause the female reproductive system gradually stops making the female hormones necessary for the reproductive cycle to work. When the body no longer produces these hormones a woman is considered to be menopausal.

What parts make-up the female anatomy?
The female reproductive anatomy includes internal and external structures.

The function of the external female reproductive structures (the genital) is twofold: To enable sperm to enter the body and to protect the internal genital organs from infectious organisms. The main external structures of the female reproductive system include:

• Labia majora: The labia majora enclose and protect the other external reproductive organs. Literally translated as "large lips," the labia majora are relatively large and fleshy, and are comparable to the scrotum in males. The labia majora contain sweat and oil-secreting glands. After puberty, the labia majora are covered with hair.
• Labia minora: Literally translated as "small lips," the labia minora can be very small or up to 2 inches wide. They lie just inside the labia majora, and surround the openings to the vagina (the canal that joins the lower part of the uterus to the outside of the body) and urethra (the tube that carries urine from the bladder to the outside of the body).
• Bartholin’s glands: These glands are located next to the vaginal opening and produce a fluid (mucus) secretion.
• Clitoris: The two labia minora meet at the clitoris, a small, sensitive protrusion that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.

The internal reproductive organs include:

• Vagina: The vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known as the birth canal.
• Uterus (womb): The uterus is a hollow, pear-shaped organ that is the home to a developing fetus. The uterus is divided into two parts: the cervix, which is the lower part that opens into the vagina, and the main body of the uterus, called the corpus. The corpus can easily expand to hold a developing baby. A channel through the cervix allows sperm to enter and menstrual blood to exit.
• Ovaries: The ovaries are small, oval-shaped glands that are located on either side of the uterus. The ovaries produce eggs and hormones.
• Fallopian tubes: These are narrow tubes that are attached to the upper part of the uterus and serve as tunnels for the ova (egg cells) to travel from the ovaries to the uterus. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. The fertilized egg then moves to the uterus, where it implants to the uterine wall.

What happens during the menstrual cycle?
Females of reproductive age (anywhere from 11-16 years) experience cycles of hormonal activity that repeat at about one-month intervals. (Menstru means "monthly"; hence the term menstrual cycle.) With every cycle, a woman’s body prepares for a potential pregnancy, whether or not that is the woman’s intention. The term menstruation refers to the periodic shedding of the uterine lining.

The average menstrual cycle takes about 28 days and occurs in phases: the follicular phase, the ovulatory phase (ovulation), and the luteal phase.

There are four major hormones (chemicals that stimulate or regulate the activity of cells or organs) involved in the menstrual cycle: follicle-stimulating hormone, luteinizing hormone, estrogen, and progesterone.

Follicular phase
This phase starts on the first day of your period. During the follicular phase of the menstrual cycle, the following events occur:

• Two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) are released from the brain and travel in the blood to the ovaries.
• The hormones stimulate the growth of about 15-20 eggs in the ovaries each in its own "shell," called a follicle.
• These hormones (FSH and LH) also trigger an increase in the production of the female hormone estrogen.
• As estrogen levels rise, like a switch, it turns off the production of follicle-stimulating hormone. This careful balance of hormones allows the body to limit the number of follicles that complete maturation, or growth.
• As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die. The dominant follicle continues to produce estrogen.

Ovulatory phase
The ovulatory phase, or ovulation, starts about 14 days after the follicular phase started. The ovulatory phase is the midpoint of the menstrual cycle, with the next menstrual period starting about 2 weeks later. During this phase, the following events occur:

• The rise in estrogen from the dominant follicle triggers a surge in the amount of luteinizing hormone that is produced by the brain.
• This causes the dominant follicle to release its egg from the ovary.
• As the egg is released (a process called ovulation) it is captured by finger-like projections on the end of the fallopian tubes (fimbriae). The fimbriae sweep the egg into the tube.
• Also during this phase, there is an increase in the amount and thickness of mucus produced by the cervix (lower part of the uterus.) If a woman were to have intercourse during this time, the thick mucus captures the man's sperm, nourishes it, and helps it to move towards the egg for fertilization.

Luteal phase
The luteal phase begins right after ovulation and involves the following processes:

• Once it releases its egg, the empty follicle develops into a new structure called the corpus luteum.
• The corpus luteum secretes the hormones estrogen and progesterone. Progesterone prepares the uterus for a fertilized egg to implant.
• If intercourse has taken place and a man's sperm has fertilized the egg (a process called conception), the fertilized egg (embryo) will travel through the fallopian tube to implant in the uterus. The woman is now considered pregnant.
• If the egg is not fertilized, it passes through the uterus. Not needed to support a pregnancy, the lining of the uterus breaks down and sheds, and the next menstrual period begins.

How many eggs does a woman have?
During fetal life, there are about 6 million to 7 million eggs. From this time, no new eggs are produced.

The vast majority of the eggs within the ovaries steadily die, until they are depleted at menopause. At birth, there are approximately 1 million eggs; and by the time of puberty, only about 300,000 remain. Of these, 300 to 400 will be ovulated during a woman's reproductive lifetime. The eggs continue to degenerate during pregnancy, with the use of birth control pills, and in the presence or absence of regular menstrual cycles.

The ovum is the part of the female reproductive system. It is located in the ovaries. It is a eukaryotic cell. The cell is haploid (A cell or an organism having half of the number of chromosomes in somatic cells) so that when a sperm cell fertilizes it, it forms a diploid zygote (A cell in diploid state following fertilization or union of haploid male sex cell and haploid female sex cell). Once it's fertilized, the female becomes pregnant.
It does NOT, however, produce sperm cells.

Ecology

Although often inconspicuous, fungi occur in every environment on Earth and play very important roles in most ecosystems. Along with bacteria, fungi are the major decomposers in most terrestrial (and some aquatic) ecosystems, and therefore play a critical role in biogeochemical cycles^[128] and in many food webs. As decomposers, they play an essential role in nutrient cycling, especially as saprotrophs and symbionts, degrading organic matter to inorganic molecules, which can then re-enter anabolic metabolic pathways in plants or other organisms.^[129][130]

Symbiosis

Many fungi have important symbiotic relationships with organisms from most if not all Kingdoms.^{[131][132][133]} These interactions can be mutualistic or antagonistic in nature, or in the case of commensal fungi are of no apparent benefit or detriment to the host.^{[134][135][136]}

With plants

Mycorrhizal symbiosis between plants and fungi is one of the most well-known plant–fungus associations and is of significant importance for plant growth and persistence in many ecosystems; over 90% of all plant species engage in mycorrhizal relationships with fungi and are dependent upon this relationship for survival.^[137]

The dark filaments are hyphae of the endophytic fungus Neotyphodium coenophialum in the intercellular spaces of tall fescue leaf sheath tissue

The mycorrhizal symbiosis is ancient, dating to at least 400 million years ago.^[118] It often increases the plant's uptake of inorganic compounds, such as nitrate and phosphate from soils having low concentrations of these key plant nutrients.^[129][138] The fungal partners may also mediate plant-to-plant transfer of carbohydrates and other nutrients. Such mycorrhizal communities are called "common mycorrhizal networks".^[139] A special case of mycorrhiza is myco-heterotrophy, whereby the plant parasitizes the fungus, obtaining all of its nutrients from its fungal symbiont.^[140] Some fungal species inhabit the tissues inside roots, stems, and leaves, in which case they are called endophytes.^[141] Similar to mycorrhiza, endophytic colonization by fungi may benefit both symbionts; for example, endophytes of grasses impart to their host increased resistance to herbivores and other environmental stresses and receive food and shelter from the plant in return.^[142]

With algae and cyanobacteria

The lichen Lobaria pulmonaria, a symbiosis of fungal, algal, and cyanobacterial species

Lichens are formed by a symbiotic relationship between algae or cyanobacteria (referred to in lichen terminology as "photobionts") and fungi (mostly various species of ascomycetes and a few basidiomycetes), in which individual photobiont cells are embedded in a tissue formed by the fungus.^[143] Lichens occur in every ecosystem on all continents, play a key role in soil formation and the initiation of biological succession,^[144] and are the dominating life forms in extreme environments, including polar, alpine, and semiarid desert regions.^[145] They are able to grow on inhospitable surfaces, including bare soil, rocks, tree bark, wood, shells, barnacles and leaves.^[146] As in mycorrhizas, the photobiont provides sugars and other carbohydrates via photosynthesis, while the fungus provides minerals and water. The functions of both symbiotic organisms are so closely intertwined that they function almost as a single organism; in most cases the resulting organism differs greatly from the individual components. Lichenization is a common mode of nutrition; around 20% of fungi—between 17,500 and 20,000 described species—are lichenized.^[147] Characteristics common to most lichens include obtaining organic carbon by photosynthesis, slow growth, small size, long life, long-lasting (seasonal) vegetative reproductive structures, mineral nutrition obtained largely from airborne sources, and greater tolerance of desiccation than most other photosynthetic organisms in the same habitat.^[148]

With insects

Many insects also engage in mutualistic relationships with fungi. Several groups of ants cultivate fungi in the order Agaricales as their primary food source, while ambrosia beetles cultivate various species of fungi in the bark of trees that they infest.^[149] Similarly, females of several wood wasp species (genus Sirex) inject their eggs together with spores of the wood-rotting fungus Amylostereum areolatum into the sapwood of pine trees; the growth of the fungus provides ideal nutritional conditions for the development of the wasp larvae.^[150] Termites on the African savannah are also known to cultivate fungi,^[151] and yeasts of the genera Candida and Lachancea inhabit the gut of a wide range of insects, including neuropterans, beetles, and cockroaches; it is not known whether these fungi benefit their hosts.^[152]

As pathogens and parasites

The plant pathogen Aecidium magellanicum causes calafate rust, seen here on a Berberis shrub in Chile.

Meiosis vs Mitosis

	Meiosis	Mitosis	Hide All Show All
Creates:	Sex cells only: Female egg cells or Male sperm cells	Makes everything other than sex cells	hide
Definition:	A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes in a diploid cell.	A process of asexual reproduction in which the cell divides in two producing a replica, with an equal number of chromosomes in haploid cell	hide
Produces:	four haploid daughter cells	two diploid daughter cells	hide
Steps:	The steps of meiosis are Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.	The steps of mitosis are Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis	hide
Discovered by:	Oscar Hertwig	Walther Flemming	hide
Type of Reproduction:	Sexual	Asexual	hide
Genetically:	Different	identical	hide
Cytokenesis:	Occurs in Telophase I & Telohpase II	Occurs in Telophase	hide
Number of Divisions:	2	1	hide
Pairing of Homologues:	Yes	No	hide
Function:	sexual reproduction	Cellular Reproduction & general growth and repair of the body	hide
Chromosome Number:	Reduced by half	Remains the same	hide
Karyokenesis:	Occurs in Interphase I	Occurs in Interphase	hide
Crossing Over:	Mixing of chromosomes	Does not occur	hide
Centromeres Split:	The centromeres do not separate during anaphase I, but during anaphase II	The centromeres split during Anaphase	hide
Occurrence of Crossing Over:	Yes	No	hide
Occurs in:	Humans, animals, plants, fungi	all organisms	hide
Number of Daughter Cells produced:	4	2	hide

---

Mitosisis a type of cellular reproduction where a cell will produce an identical replica of itself with the same number and patterns of genes and chromosomes.

Meiosis, on the other hand, is a special process in cellular division where cells are created containing gene patterns of different types and combinations with 50% of the number of chromosomes of the original cell.

Meiosis is used in sexual reproduction of organisms to combine male and female, through the spermazoa and egg, to create a new, singular biological organism. Mitosis is used by single celled organisms to reproduce, or in the organic growth of tissues, fibers, and mibranes.

Mitosis vs. Meiosis: Process Differences

Mitosis is a method of reproduction for single celled organisms that reproduce asexually. An identical version of the organism is created through splitting of the cell in two. Meiosis may result in millions of spermazoa and egg cells with unique genetic patterns. The mating of the two cells formed by meiosis results in a unique genetic offspring of the same species. Meiosis is a major factor in evolution, natural selection, and biodiversity. The processes of cellular division shown in mitosis and meiosis are present in all manner of life forms including humans, animals, plants, fungi, and single celled organisms and species. Essentially any cell based organism of which all organic life is based will exhibit some form of mitosis and meiosis for growth and reproduction of the individual and species.

Different Stages of Mitosis and Meiosis

Mitosis: Interphase- Preprophase- Prophase - Prometaphase - Metaphase- Anaphase -Telophase -Cytokinesis.

Meiosis: Prophase - Metaphase - Anaphase - Telophase.

An overview of the process and phases of meiosis

The process of mitosis

Mitosis vs Meiosis - Differences in Purpose

Both Meiosis and Mitosis are found in complex organisms which reproduce sexually. Mitosis may be used for human growth, the replenishment of depleted organs and tissues, healing, and sustenance of the body. Identical versions of cells can be created to form tissues through Mitosis. Meiosis is a special process reserved for the creation of the egg and sperm cells. The same patterns may be found in many species of plant and animal cell reproduction.

Significance of Mitosis vs. Meiosis

The importance of mitosis is the maintenance of the chromosomal set; each cell formed receives chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell.

Occurs in

Meiosis is found to occur in Human, animals, plants while Mitosis is found in single-cell species as well.

History

Meiosis was discovered and described for the first time in sea urchin eggs in 1876, by noted German biologist Oscar Hertwig.

Walther Flemming discovered the process of Mitosis in 1882.

Evolution of mitosis vs. meiosis

Mitosis as a form of reproduction for single-cell organisms originated with life itself (around 4 billion years ago). Meiosis is thought to have appeared 1.4 billion years ago.

Chromosomal pattern comparison

In mitosis, each daughter cell ends up with two complete sets of chromosomes while in meiosis, each daughter cell ends up with one set of chromosomes.

Both mitosis and meiosis are studied by scientists generally by using a microscope to identify and classify chromosomal patterns and relationships within the cell’s structure. An understanding of the way cells synthesize chromosomes for reproduction can be applied in bio-machines and nano-technology. Transplantation of genes and chromosomes through injection and implantation is used to experiment with bio-engineering and cloning. Understanding the process through which cells replicate also has application in medicine and the study of health and disease.

Difference Between Mitosis and Meiosis

• Categorized under Science

Mitosis vs Meiosis

Meiosis and Mitosis describe cell division in eukaryotic cells when the chromosome separates.

In mitosis chromosomes separates and form into two identical sets of daughter nuclei, and it is followed by cytokinesis (division of cytoplasm). Basically, in mitosis the mother cell divides into two daughter cells which are genetically identical to each other and to the parent cell.

Phases of mitosis include:

1. Interface -where cell prepares for cell division and it also includes three other phases such as G1 (growth), S (synthesis), and G2 (second gap)
2. Prophase – formation of centrosomes, condensation of chromatin
3. Prometaphase- degradation of the nuclear membrane, attachment of microtubules to kinetochores
4. Metaphase- alignment of chromosomes at the metaphase plate
5. Early anaphase- shortening of kinetochore microtubules
6. Telophase- de-condensation of chromosomes and surrounded by nuclear membranes, formation of cleavage furrow.
7. Cytokinesis- division of cytoplasm

Meiosis is a reductional cell division where the number of chromosomes is divided into half. Gametes formations occur in animal cell and meiosis is necessary for sexual reproduction which occurs in eukaryotes. Meiosis influence stable sexual reproduction by halving of ploidy or chromosome count. Without meiosis the fertilization would result in zygote with twice the number of the parent.

Phases of meiosis include:

1. Meiosis I – separation of homologous chromosomes and production of two haploid cells (23 chromosomes, N in humans)
2. Prophase I – pairing of homologous chromosome pair and recombination (crossing over) occurs
3. Metaphase I – Homologous pairs move along the metaphase plate, kinetochore microtubules from both centrioles attach to the homologous chromosomes align along an equatorial plane.
4. Anaphase I – shortening of microtubules, pulling of chromosomes toward opposing poles, forming two haploid sets
5. Telophase I – arrival of chromosomes to the poles with each daughter cell containing half the number of chromosomes
6. Meiosis II – second part of the meiotic process with the production of four haploid cells from the two haploid cells

Summary:
Mitosis – separation of chromosomes into two identical sets of daughter cells

Meiosis- reductional cell division and the number of chromosomes is divided into half; it is essential for sexual reproduction, and therefore it occurs in eukaryotes

Mitosis vs. Meiosis

Both mitosis and meiosis are mechanisms that describe cell division. The difference is particularly noticeable when one looks at the DNA in the cell's nucleus. After mitosis, each of the daughter cells will have exact same DNA strands, while after meiosis each daughter cell will only have half of the DNA strands. (Sometimes the division is not exactly half/half, but that is not important for this answer).

Because meiosis only has half the information that the parent cell had, the cell is (as far as we know) unable to reproduce by itself. The reason for meiosis is for reproduction of a multi-cellular organism as well as genetic diversity due to crossing over. One daughter cell (from the male of the species) will try to find a compatible daughter cell (from the female of the species) and fertilize it. This then becomes and embryo and the specie has successfully reproduced. And this is how you, the reader, came into existence.
 

Other characteristics:

• Parent cell - full set of chromosomes in both mitosis and meiosis (2n).
• Number of divisions - mitosis 1; meiosis 2.
• Chromosome number of daughter cells - mitosis full set (2n) and meiosis half set (n).
• Crossing over - mitosis no; meiosis yes
• Paired homologues - mitosis no; meiosis yes
• DNA of daughter cells - mitosis identical to parent; meiosis daughter cells different
• Number of DNA replications - mitosis 1; meiosis 2
• Number of daughter cells - mitosis 2; meiosis 4
• Type of cells - mitosis somatic; meiosis sex cells