Female reproductive system
There are several organs and tissues that make up the female
reproductive system, these include that ovaries, fallopian tubes, uterus,
vagina, vulva, mammary glands and breasts. They are also involved in producing
and transporting gametes and in the production of sex hormones. The female
reproductive system is also responsible for fertilizing the ova by the sperm
cells and supporting the development of the offspring during the process of
pregnancy and infancy.
(book) remember to cut it
The ovaries are located in the abdominal cavity, they are
held in place by ligaments. The surface of the ovaries is covered with germinal
epithelial tissue which consists of cells called Oogonia. These cells produce
ovum. Oogonia cells undergo mitosis to produce primary oocytes, diploid cells,
and produce follicle cells which are responsible for protecting and nourishing
the egg before it is released into the oviducts during ovulation.
The funnel of the fallopian tube is located near to the
ovary. This funnel is lined with fimbrae, finger like structures which, when
activated by hormones, catch a released egg and move it down into the fallopian
tube. The fimbrae is lined with cilia.
Secondary oocytes (the oocyte that is created by the first
meiosis division) are pushed along the fallopian tube by the cilia and the
muscles of the fallopian tubes. These fallopian tubes lead to the uterus and
join the uterus at a point called the uterine horn.
Myometrium is the name of the smooth muscle that makes up
the uterus. The uterus is lined with the endometrium which is a tissue with high
blood supply. The Blastocyst will embed into this tissue.
The bottom end of the uterus has an opening which is called
the cervix. The cervix leads into the vagina which allows the cervix to be
connected to the outer environment through the vulva.
The vulva is made up of several folds of skin which are
called the labia. There are two inner folds called the labia minora and two
outer folds called the labia majora.
The clitoris is also a part of the female reproductive
system, it is a small body of erectile tissue which is enclosed within the
labia. It is a highly sensitive tissue which swells with blood during sexual
Male reproductive system
The male reproductive system is responsible for the
production, maintenance and transportation of sperm and protective fluids. The
sperm and protective fluids are to be discharged within the female reproductive
tract during sexual intercourse.
There are three important glands within the male
reproductive system which have ducts joining the urethra. These glands are
called the seminal vesicles, prostate gland and the Cowper’s gland. These
glands are responsible for nourishing the sperm and raising it’s pH, they do
this by secreting fluids. The purpose of making the sperm alkaline is to
neutralise the acidic conditions in the urethra and the vagina. If the sperm
had a more acidic pH the chances of conception could be impaired.
Each testis is broken up into several different compartments
called lobules which contain the seminiferous tubules. These seminiferous
tubules are lined with a layer of cells which are called the germinal
epithelial. Inside the seminiferous tubules are cells called spermatogonia
which produce sperm. These spermatogonia cells undergo mitosis in order to
produce primary spermatocytes (diploid cells).
The seminiferous tubules connect together in order to form a
network of tubules, this network is called the vas efferentia. These then
connect and form the epididymis which is a long tube and lies outside of the
The epididymis connects to the vas deferens which leaves the
scrotal sac and then joins the urethra. Sperm is stored in these sections of
the testis until ejaculation occurs. During the process of ejaculation, sperm
and fluids are released into the urethra are released from the end of the penis.
This mixture of sperm and fluids is called semen.
Gamete production is known as gametogenesis, this happens in
the gonads. Sex cells are developed in the testes and ovaries during
gametogenesis through the process of meiosis. During gametogenesis meiosis
occurs to produce gametes which are haploid. This is done in order to produce a
diploid offspring during fertilisation.
Spermatogenesis is the process of forming sperm cells in the
testes. This process takes place in the seminiferous tubules and begins when a
human male reaches puberty. Spermatogonia cells undergo mitosis to produce
primary spermatocytes. These primary spermatocytes then divide via meiosis in
order to form secondary spermatocytes which develop into spermatids.
Spermatids contain the correct number of chromosomes in
order to be classified as gametes but they lack the structure of a sperm cell.
They do not have certain organelles like the flagellum which can help them swim
to the ovum.
In order for the spermatids to develop into mature sperm
cells they need to be nourished and protected. There are Sertoli cells present
in the wall of the seminiferous tubules which secrete a fluid that nourishes
and protects the spermatids.
Testosterone stimulates the Sertoli cells, testosterone is
released by a cell near the seminiferous tubules called the Leydig cells.
Hormonal control of Spermatogenesis
The hypothalamus releases a hormone called the
Gonadotropin-releasing hormone (GnRH) which stimulates the anterior pituitary
gland to release Follicle-stimulating hormone (FSH) and Luteinizing hormone
The FSH travels to the testis to the spermatogenic cells in
the seminiferous tubules which will stimulate spermatogenesis.
The LH is going to travel to the interstitial cells which
will then release testosterone. In certain target tissues testosterone will be
converted into dihydrotestosterone (DHT). DHT and testosterone will bind to
certain target receptors called androgen receptors in specific target tissues
and be responsible for secondary sexual characteristics such as facial hair in
Testosterone and FSH also travel to the Sertoli cells which
will release androgen binding protein (ABP). The effect of ABP is the exertion
of tropic effects on spermatogenesis.
When spermatogenesis will reach a certain level the Sertoli
cells will release inhibin which inhibits the FSH release. Testosterone will
also inhibit at the level of the anterior pituitary gland and the hypothalamus.
Oogenesis is the process of forming ova in the ovaries. It
begins before birth while the female is a foetus. Oognoia divide in order to
form primary oocytes. (book)
Hormonal control of Oogenesis
Cells which are located within the germinal epithelium
divide in order to form follicle cells. These follicle cells then surround
primary oocytes to form primary follicles. Meiosis then begins in the primary
oocytes but stops at prophase 1. (book)
During puberty FSH is produced by the pituitary gland and
stimulates primary follicle cells to develop. A few follicles will begin to
develop each month but usually only one of them would mature to form a Graafian
follicle. FSH also stimulates the formation of oestrogens.
Inside of the Graafian follicle the primary oocyte completes
the first meiotic division in order to create primary oocytes and a polar body.
The follicle cells which surround the secondary oocyte grow and several fluid
filled spaces form.
The Graafian follicle matures and travels to the surface of
the ovary. LH instigates the rupture of the mature Graafian follicle which
allows secondary oocytes to be released, this process is called ovulation. (book)
The menstrual cycle
The menstrual cycle is a period of time which starts on the
day that a woman’s period begins until the day prior to the next period. The
menstrual cycle begins during puberty from the age of 10 and ends when the
woman reaches the age of 55. This is because of menopause, menopause is caused
by the decline of oestrogen levels which prevents the regulation of the
The menstrual cycle is divided
into multiple phases: The menstrual phase, the follicular phase, the ovulation
phase and the luteal phase.
This phase begins on the first
day of menstruation and lasts until the fifth day of the menstrual cycle.
During this phase of the cycle the uterus sheds its inner lining of soft tissue
and blood vessels which exits the vagina in the form of menstrual fluid. It is
common for females to experience abdominal cramps which are caused by
contractions of the uterine and abdominal muscles. These muscles contract in
order to get rid of menstrual fluid.
This phase begins at the same
time as the menstrual phase, but it lasts until the thirteenth day of the
menstrual cycle. During this phase the pituitary gland secretes a hormone
called FSH which stimulates the eggs in the ovaries to grow. One of those egg
cells will mature inside of a follicle, it takes an egg 13 days to reach
maturity. While the egg cell is maturing a hormone called FH stimulates the
uterus to form an endometrium (lining of blood vessels and soft tissue).
This phase begins on the
fourteenth day of the cycle. During this phase the pituitary gland releases LH
which causes the ovary to release the mature egg cell. The released egg is
swept into the fallopian tube by the cilia of the fimbriae.
This phase begins on the fifteenth
day and lasts until the end of the menstrual cycle. During this phase the egg
cell which was released during the ovulation phase is kept in the fallopian
tube for 24 hours. If the egg cell isn’t penetrated by a sperm cell within that
time, the egg cell will be destroyed. At the end of this phase the LH gets used
up and the next stage of the cycle continues.