Investigation Of Reproduction And Development In A
nimalsInvestigation of Reproduction and Development in Animals
Due Date: 12/9/96
Cycles, Conception and Contraception
Fertility is the condition of being fertile. The aim of contraception is to
inhibit fertility in individuals, hence, slowing population growth. The system
by which all female contraception must operate: the menstrual cycle.
What is the menstrual cycle? and what hormones are involved in controlling it?
After puberty, the female produces an egg each month. Other changes take place
on a cyclic basis including the uterus lining and hormone levels. These changes
are called the menstrual cycle. Follicle stimulating hormone (FSH) from the
pituitary gland stimulates the growth of follicles in the ovary. Follicles
produce oestrogen that stimulates the pituitary to produce leutinising hormone
(LH). As LH increases the size of the follicle increases until an egg is
released. The corpus luteum formed in the follicle secretes progesterone that
prepares the lining of the uterus for pregnancy. If fertilisation does not occur
the lining of the uterus is discharged from the body in the process called
What is the birth control pill?
The combined oral contraceptive pill (the pill) is a reversable, hormonal
method of birth control. The pill consists of a mixture of two synthetic
hormones similar to oestrogen and progesterone, the woman’s natural hormones
which regulate the menstrual cycle. The pill is on of the most popular methods
of birth control.
How does it work?
The pill basically prevents ovulation, therefore, the ovaries can’t release a
mature egg. Without an egg for the sperm to fertilize , a woman cannot get
pregnant . The hormones also increase cervical mucus, making it difficult for
sperm to pass into the uterus.
How effective is the pill?
If used correctly, the pill is highly effective. It has a less than one percent
failure rate. However, because many people misuse it, the actual failure rate is
more like three percent. The pill does not provide protection against sexually
How are pills used?
One pill must be swallowed at the same time every day. It is not any single
pill, but the day-to-day process of taking the pill which provides protection
What is infertility?
Infertility in humans and other species(animals) is the inability to concieve or
carry a pregnancy to a live birth. The causes of infertility can be identified
in some cases. The majority of cases relate to female factors (50%), 40% relate
to male factors and 10% aree unknown. Infertility sometimes may serve as a
combination of both male and female factors.
If the cause of infertility is known, treatment of some kind may be available.
In other cases a problem may disappear on its own and fertility is restored. For
many couples, about 40% of those affected, there is no solution to their
Now days, there are a range of technologies and options available to couples
wishing to have children of their own. These methods include: donor insemination,
IVF ( in vitro fertilisation), ZIFT, GIFT and so on.
What is IVF?
IVF involves fertilization outside the body in an artificial environment. This
procedure was first used for infertility in humans in 1977,in England. To date,
thousands of babies have been delivered as a result of IVF treatment. The IVF
procedure has become simpler, safer and more successful over the years.
What types of infertility can be helped by IVF?
IVF is a good option for a couple in several instances. The most common reasons
for this procedure is blocked or damaged fallopian tubes. Through IVF, the
damaged fallopian tubes are bypassed and the fertilization which usually takes
place within fallopian tubes is now performed in the human embryo culture
laboratory. Other factors that might lead to the need for IVF include low sperm
count, endometriosis and unexplained infertility which has not responded to
other courses of treatment.
How is procedure carried out?
To accomplish pregnancy as a result of IVF several steps are involved:
– Stimulation of the ovary to produce several fertilizable eggs. – Retrieval of
the eggs from the ovary. – Fertilization of the eggs and culture of the embryos
in the IVF laboratory. – Placement of the embryos into the uterus for
implantation (embryo transfer or ET).
Encarta Encyclopedia, Microsoft 96′ Kinnear, Judith, Book One: Nature of Biology,
The Jacaranda Press, Sydney, 1992. Winston, Robert, Infertility, A Sympathetic
Approach, Optima Book, Great Britian, 1994. World Book Encyclopedia, World Book
Inc, Chicago, 1991. The Human Body, World Book Inc, Chicago, 1990.