Investigation Of Reproduction And Development In Animals

Essay, Research Paper

Investigation 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 menstruation.

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 transmitted diseases.

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 against pregnancy.

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 infertility.

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).

Bibliography:

Encarta Encyclopedia, Microsoft 96

Kinnear, Judith, Book One: Nature of Biology, The Jacaranda Press, Sydney, 1992.

Netscape

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.