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            It is said that the greatest gift of
all is life. Humans or more specifically the reproductive system is able to
provide this gift. The reproductive system is an essential system for the
continuation of the human species. The system involves many organs that work
together to form life. The reproductive system is on the complex side, due to
the part that males and females have different reproductive systems. However,
the female reproductive system is the more complicated one. Although the female
reproductive system is more complex is does not outweigh the importance of the
male reproductive system, as for both are essential in the creation of an
offspring.

            The female reproductive system
consists of ovaries, fallopian tubes, the uterus and the vagina. The main
purpose of the reproductive system is to achieve fertilization. Which is also
known as pregnancy, which occurs when a sperm and egg join to create a diploid
zygote.  Eggs in the female body are
located in the ovaries and in order for an egg to be fertilized it must be
present in fallopian tube. The process by which the egg travels from the ovary
to the fallopian tube is called ovulation. Normally around the age of 12 or 13,
the female body physical develops to be able to reproduce sexual, this is
called puberty. During puberty the female body enters a monthly cycle, called
the menstrual cycle, in which the female body sheds the
lining of the uterus.

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            The average menstrual cycle takes about 28 days, but that
does not mean every female body has the same cycle. Cycles
range from 21 to 35 days in adults and from 21 to 45 days in young teen.
However, menstruation, physical bleeding, only occurs between 3 to 5
days. The menstrual cycle is broken down in three main phases: the menstrual
(“destructive”) phase, also called menses; the follicular (“proliferative” or
“estrogenic”) phase and the luteal (or ” secretory,” “progestational”) phase”
(Jones, 54). The first day of when menstruation begins is marked as the first
day of the menstrual phase. The menstrual phase can last from 1 to 7 days
however, it usually last from 3 to 5 day’s. The follicular phase begins at the
end of the menstrual phase, which is normally the day after menstruation stops.
The follicular phase last until ovulation, which occurs around day 14 to day 16
of the menstrual cycle depending on how long one’s cycle is. The luteal phase
lasts from ovulation to the beginning of the next menstruation.

            During the menstrual phase, the
stratum functionalis of the endometrium, the scientific name for the lining of
the uterus, starts to degenerate. The tissue starts to degenerate because the
blood vessels that supply nutrients and oxygen to the tissue begin to
“constrict and dilate spasmodically” (Jones, 55). The vessels then bleed which
is apart of the uterus lining degenerating. During the menstrual phase four
hormones are present which are categorized as either, pituitary hormones ,
which are released from the brain and travel in the blood to the ovaries, and
steroid hormones. Follicle stimulating hormone (FSH) and luteinizing hormone
(LH) are pituitary hormones while estrogen and progesterone are steroid
hormones(. All four hormones are low on day 1 of the cycle. However, by day 3 FSH
causes some follicle to increase in size because the “low levels of estrogen
and progesterone signal the pituitary gland to produce FSH” (Hormone Imbalance). As follicles grow
they begin to secrete estrogen so estrogen blood levels increase also by day 3.
 However, progesterone
levels stay low throughout the menstrual phase.

            Right after the menstrual phase
comes the follicular phase, which is normally day 14 of the menstrual cycle.
This cycle normally marks the halfway point of the menstrual cycle, having the
next menstrual usually starting 2 week later. 
During this phase the rise in estrogen level from the
increase of follicle activates a rush in the amount of luteinizing hormone that
is produced by the brain. This causes the follicle, which is a fluid-filled sac in the ovary containing eggs, to
release an egg from the ovary. The releasing of the egg is a process ovulation.
During this process the egg that is released is captured by finger-like
projections called fimbriae at the end of the fallopian tubes. During the
follicular phase, there is an “increase in the amount and thickness of mucus
produced by the cervix (lower part of the uterus)” (The Female Reproductive System).
The thick mucus captures the man’s sperm and helps it to move towards the egg
for fertilization, if sexual intercourse has taken place during this phase.

            The
luteal phase begins after ovulation and is
considered the last phase of the menstrual cycle. In this phase once the
egg is released from the ovary, the empty ovary changes its structure, which is
called the corpus luteum. The corpus luteum secretes steroid hormones,
estrogen and progesterone. Progesterone prepares the uterus to implant a fertilized
egg, which is if intercourse has taken place. The fertilized egg, which is
also called the embryo, will travel through the fallopian tube and implant itself
onto the uterus. Since the egg is fertilized pregnancy occurs in which the
embryo will turn into a fetus. However, if the egg attaches to the uterus and
is not fertilized, the uterus will recognize this and the lining of the uterus will
start to degenerate. This now returns to the menstrual phase in which
menstruation begins again.

            As
there is an age for the beginning of the menstrual cycle there is also an end.
The end of the menstrual cycle is called menopausal period, also just known as
menopause. Menopause normally occurs between the ages 45 and 52 years, but it
can occurs as early as 42 or as late as 55. Menopause occurs due to aging and
the ovaries no longer being active. The reproductive organs also become
smaller, “no more ova mature; therefore no ovarian hormones are produced. An
early menopause may occur if the ovaries are surgically removed or are
destroyed by radiation or chemotherapy”(Hinkle).

            The
alternative of menstruation is fertilization, which leads to pregnancy. Human’s
use one of the two types of fertilization, which internal. In order to
understand the aftermath of fertilization, the general information of the
internal female reproductive system needs to be recognized. Aside from the
ovaries, the vagina and uterus are also very important. The vagina is a
tubular-shaped canal in which semen is deposited during sexual intercourse, and
it is also the pathway for the flow of menstruation blood. The semen travels
through the vaginal canal to get to the fallopian tubes to inseminate the egg.
“The canal is also referred to as the birth canal because the baby moves out of
the uterus and through the vagina during childbirth” (Freeman). 

            The
major reproductive organ is the uterus. The uterus is the site of fetus
development and is a pear-shaped muscular organ.
Before a women’s first pregnancy, the uterus is around the size and shape of a
pear and is narrow. However, after childbirth, the uterus expands in size, and
then reverts back after menopause. The uterine wall has three layers. The
endometrium, which is the most inner layer, is 
“highly vascular and responds to hormone stimulation to prepare to
receive the developing ovum” (Hinkle). This is the tissue that degenerates if
fertilization does not occur which results in menstruation. However, the tissue
also degenerates after childbirth. The myometrium is the middle layer, which is
made up of smooth muscle layer. The myometrium itself had three layers. The
outer layer is made up of fibers that help eject the fetus. The middle layer of
the myometrium is made up of fibers that interlace with blood vessels to help
control blood loss after childbirth. The inner layer of the myometrium is made
up of fiber that helps keep the cervix closed during pregnancy. The third layer
of the uterine wall is the parietal peritoneum, which covers the uterus
and holds it in place.

            The uterus also has four parts: the
cervix, the fundus, the corpus and the isthmus. The cervix is
the opening of the uterus and projects into the vagina. The large round area
above the fallopian tubes is the fundus. The isthmus connects the cervix and
corpus. Corpus is the main part of the uterus and is located between the fundus
and isthmus. The cervix is the major part of the uterus in which it produces
mucus, which is an important factor in fertility awareness. The uterus is coated with this
mucus membrane rich in the blood capillaries to form the placenta which responsible for providing nourishment to the
fetus during pregnancy through the umbilical cord.

            The
umbilical cord only develops during pregnancy through embryonic tissue. This
cord is essential for the growth of the fetus as it provides a the exchange of
gases, nutrients and wastes between the mother and the fetal blood, but the
“maternal and fetal blood do not commingle”(Freeman). The placenta is another
organ that develops during pregnancy and helps develop the fetus. The placenta
produces many hormones, including large amounts of progesterone and estrogen.
The production of these steroid hormones suppresses GnRH
(Gonadotropin-releasing hormone), which stimulates the pituitary gland to
release luteinizing hormone (LH) and follicle-stimulating hormone(FSH).  By suppressing GnRH prevents the ovulation of
more follicles, hence menstruation does not occur during pregnancy.

            The
female reproduction system is not the only reproductive system involved in
creating human life, the male reproductive system is just as vital. When
compared to the female reproductive system, the male reproductive system is
much simpler and doesn’t extend during pregnancy because the male does not
carry the fetus. The reproductive organs of males include, “a pair of testes and excretory ducts (such as epididymis,
vas deferens, and ejaculatory duct), seminal vesicles, the prostate, the bulbourethral
glands, and the penis” (SEER).

            The sperm, or semen, is the male
reproductive cell. Sperm is produced in the testes and is stored in the
epididymis. “When the sperm leave the testes, they are immature and incapable
of fertilizing ova. They complete their maturation process and become fertile
as they move through the epididymis”(SEER). The vas deferens is a muscular
tube that moves the sperm from the epididymis to the ejaculatory duct, where
the sperm mixes with accessory fluids. The accessory fluids form in the seminal
vesicles, prostate gland and bulbourethral gland. The accessory fluids build
onto the sperm to create semen, which can fertilize an egg. The semen passes through
the ejaculatory duct and enters the urethra that passes through the penis, in
which the semen can be released from the male body through ejaculation.

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