Hormones regulate the functions of many organs and cells. Hormones are chemicals that are secreted (produced) by __________, that are transported to all parts of the body through the __________, and affect specific target organs.
Examples of Hormones
Several hormones are involved in the menstrual cycle of a woman which you need to know in detail.
During the 28 day menstrual cycle the old lining of the __________ is shed and then a fresh lining built up again in readiness for a possible pregnancy. The shedding of the lining which is accompanied, by a loss of blood, is called __________ and marks the beginning of a new cycle.
On the 14th day of the cycle a mature __________ (Ovum) is released from one of the __________ in a process known as __________.
If the egg is fertilised by the __________, the lining of the uterus provides protection and food for the developing embryo. If the egg is not __________ the lining of the uterus and the egg are shed from the body and this is called a __________.
Click image to see cycle in full
Use the diagram above to complete the following:
FSH which is secreted by the __________ and causes eggs to __________ in the ovaries, and also stimulates the ovaries to produce hormones including __________.
Oestrogen which is secreted by the __________ and inhibits the further production of __________ as well as stimulating the __________ to produce a hormone called __________.
Because of this understanding we can use artificial hormones to help control fertility:
Women can take oral (by mouth) contraceptives which contain the hormone __________ which inhibits FSH production so that no eggs mature. This practically reducing the chance of getting pregnant to zero. However if just one daily pill is missed then the women may become unprotected.
We must also consider the reported side effects such as:
__________ can be given as a 'fertility drug' to a woman whose own level of hormone is too low to stimulate eggs to mature. Fertility treatments increase a woman's chance of becoming pregnant, although the treatment may not always work.
On the other hand, because the treatment boosts the production of mature eggs, multiple conceptions sometimes occur, with twins or triplets being expected. This increases the risk of complications in pregnancy and childbirth, and may lead to premature or underweight babies.
'In-vitro Fertilisation' (IVF) is the process of hormonally controlling the ovulatory process, removing eggs from the woman's ovaries and letting sperm fertilise them in a 'test tube'. In fact 'In Vitro' means 'in glass'. The fertilised egg (zygote) is then transferred to the patient's __________ with the intent to establish a successful pregnancy.
If FSH is injected into the patient then several mature eggs can be produced at once. This doesn't normally happen because the __________ produced by the __________ would normally stop the production of FSH. Injecting FSH allows a number of eggs to be havested at once, increasing the chance of success while minimising trauma to the patient.
Some people worry about the ethical implications of IVF. They are concerned that couples may only want fertilised eggs with 'desirable' qualities - so called 'designer babies'. For example, they may want a girl if they have lots of boys in the family, or they may wish to avoid producing a baby with an inherited defect.