Hormonal Control of Reproductive System
The Female Reproductive System
The female reproductive system:
Fallopian Tube – During the menstrual cycle, the ova, which are produced in the ovaries, are transported to the
uterus via these fallopian tubes every month (this varies depending on the length of each individual’s menstrual
cycle). The ova remain in the fallopian tubes for around 24 hours. If they are not fertilised in this time, the
endometrium of the uterus breaks down and passes through the vagina. When sperm is present, and fertilisation
takes place within the fallopian tubes, the fertilised eggs are transported to the uterus for implantation.
Ovary – The ovaries are responsible for maintaining the female reproductive system health. They secrete the two
main hormones involved in female reproduction which are oestrogen and progesterone. The ovaries are also the site
of egg cell production, often referred to as the ova.
Uterus – The uterus is the location where a developing foetus is housed and nourished prior to birth, should
fertilisation have taken place. When fertilisation has not taken place, the lining (endometrium) of the uterus sheds
and passes through the vagina.
Cervix – The cervix is the lower region of the uterus. The cervix is the area that the sperm passes through to travel to
fertilise any eggs.
Endometrium – The endometrium is the inner lining of the uterus. Each menstrual cycle, this inner lining thickens
itself and renews itself in preparation for pregnancy (the embryo implanting in the uterus). When fertilisation does
not take place, this inner lining sheds and passes through the vagina as part of menstruation.
Myometrium – The myometrium is the middle layer of the wall of the uterus. It is made up of smooth muscle cells
which can also be referred to as uterine myocytes. The main function of the myometrium is to induce uterine
contractions to assist in the birth of a baby.
Uterine Horn – The uterine horns support the transportation of sperm up to the fallopian tubes for fertilisation.
Fimbriae – Fimbriae are long projections at the end of fallopian tubes. Eggs move through these to get to the uterus.
Vagina – The vagina provides a passageway for blood when the shedding of the endometrium occurs in females. It
also is essential in the process of conception, as it is required for sexual intercourse with a male. It is also where the
baby exits the woman’s body during childbirth.
, Hormones Involved in the Female
Reproduction System
In females, reproductive hormones
are normally made and produced in
the ovaries. Progesterone and
oestrogen are the two main
examples of female reproductive
hormones which help in the
development and maintenance of
the sex characteristics in females.
They are vital in the processes of the
menstrual cycle, fertility, and
pregnancy.
The Menstrual Cycle
The menstrual cycle is the series of
changes within females that occurs
monthly. These changes occur in
preparation for pregnancy. The
length of the menstrual cycle is
calculated from the first day of the
first period to the next. This length
can vary for each individual, and
typically varies between 21 to 35
days. It is not the same for every woman. Oestrogen is the hormone which regulates the menstrual cycle. It is the
hormone responsible for thickening the endometrium and making it more receptive to a fertilised egg. Oestrogen
levels tend to peak just before ovulation begins. Menstruation, the period, can last between two and seven days,
and again, varies between women. There are four phases of the menstrual cycle.
Menstruation
Menstruation is the phase where women have their period. This stage occurs when fertilisation has not taken place,
and the uterine lining (endometrium) sheds. The endometrium would have thickened and renewed since the last
menstrual cycle in preparation for potential pregnancy. When pregnancy does not occur, this lining sheds as it is not
needed for embryo implantation, which results in a period. The lining sheds and blood is released through the
vagina. This stage can last between two and seven days depending on the individual. Women may use various
methods to absorb the blood once it exits through the vagina. These methods consist of sanitary towels, tampons,
and menstrual cups.
The Follicular Phase
The follicular stage begins on the first day of a woman’s period (menstruation) and ends when ovulation begins.
During this stage, the hypothalamus triggers the pituitary gland to release the hormone known as FSH (follicle
stimulating hormone). This hormone prompts the ovaries to produce between 5 and 20 small cysts (called follicles)
which appear on the surface of the ovaries. One immature egg is stored in each follicle. In normal circumstances,
one follicle only will mature into an egg, and the others will die. This stage usually occurs at day 10 of an average 28-
day menstrual cycle. This growth of follicles is what stimulates the rise in oestrogen levels and, subsequently, the
endometrium of the uterus thickening in preparation for a potential pregnancy. The increased levels of oestrogen
prompt the hypothalamus to release GnRH (gonadotrophin-releasing hormone). This hormone instructs the pituitary
gland to increase the levels of luteinising hormone and follicle stimulating hormone, in preparation for ovulation.
Ovulation
Women are born with all of their eggs. Just before ovulation begins, oestrogen levels increase. This is because
oestrogen makes the endometrium of the uterus thicker and more receptive to a potential fertilised egg. During
