This leaflet gives a brief overview of the female reproductive system.
The organs and structures of the female reproductive system give women the ability to produce ova (an ovum is one egg, ova means multiple eggs) to be fertilised by sperm. They also provide a place for the fetus (baby) to grow and develop. Other structures such as the breasts give the mother the ability to feed and nourish a baby after birth.
The organs of the female reproductive system are found both internally, in the pelvis, and externally (outside the main body cavity).
The organs found inside the body include:
The external structures of the female reproductive system include parts of the vagina, and the breasts. The labia, the clitoris and a number of glands are all parts of the vagina found externally. Together these organs are known as the vulva.
Its main function is to give women the ability to produce ova to be fertilised, and the space and conditions to allow a fetus to develop. In order for this to happen, the female reproductive system also has the structures necessary to allow sperm from a man to meet the ova of a woman. To do all this the female reproductive system makes its own hormones that help to control a woman's monthly cycle. These hormones cause the development and release of ova so that they can be fertilised. This process is called ovulation. They also prevent ovulation during pregnancy.
The activity of the female reproductive system is controlled by hormones released both by the brain, and the ovaries. The combination of all these hormones gives women their reproductive cycle.
The length of the reproductive (or menstrual) cycle is usually between 24-35 days. During this time an ova is developed and matured, and the lining of the uterus is prepared to receive a fertilised egg. If a fertilised egg is not implanted into the uterus, the lining of the uterus is shed and is expelled from the body. This is the bleeding known as menstruation (period). Traditionally, the first day of bleeding is known as day one of the reproductive cycle. The key event in the cycle is ovulation, the release of a mature ovum (egg) from the ovaries. This usually takes place around the 14th day of a 28-day cycle. The first part of the cycle is concerned with developing an ovum. What happens in the second part of the cycle depends on whether the ovum is fertilised.
There are five main hormones that control the reproductive cycle. Three are produced in the brain, while the other two are made in the ovaries.
During the last few days of the cycle, around 20 small immature ova begin to develop in the ovaries. This continues throughout the menstrual cycle. FSH and LH encourage the growth of these ova. As they grow, the ova also start to release increasing amounts of oestrogen. The amount of oestrogen produced reduces the amount of FSH released. This helps to prevent too many ova growing at the same time. Eventually one ovum outgrows the rest.
While this is happening in the ovaries, the oestrogen produced also stimulates the repair of the lining of the uterus.
The next stage in the cycle is the release of the mature ovum from the ovaries into the pelvis. By this point in the cycle, levels of oestrogen are high. Previously, medium levels of oestrogen reduced the amount of FSH and LH released. Now this high level of oestrogen is the signal for more FSH and LH to be released. LH causes the ovum to burst through the outer layer of the ovary. Usually the ovum is then swept into the uterine tubes.
Next the cells remaining when the ovum leaves the ovary become the corpus luteum. This special group of cells is capable of producing several different hormones, including progesterone and oestrogen. These hormones encourage the growth and maturation of the lining of the uterus.
What happens next depends on whether the ovum is fertilised by sperm. If the ovum is fertilised, the corpus luteum continues to produce hormones. Another hormone called human chorionic gonadotrophin (hCG) stops the corpus luteum from breaking down. The cells covering the embryo produce hCG. It is the hormone detected in pregnancy tests.
If the ovum is not fertilised, the corpus luteum can only live for a further two weeks. As it begins to break down, it releases fewer of its hormones. As the levels of progesterone and oestrogen go down, they no longer control the levels of GnRH, FSH and LH. So, these hormones increase and new ova begin to develop - the start of a new cycle. In the uterus the decrease in progesterone stimulates the release of chemicals that eventually cause the lining of the uterus to die off. This is the blood flow experienced during menstruation.
From Gray's Anatomy Online
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