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Understanding the Female Reproductive System

In order to conceive a baby, both the male and female reproductive systems must be functioning.

For women, this means:

  • A viable egg (i.e., one that is capable of being fertilised by a sperm and developing into an embryo) must be released as a result of successful ovulation; and
  • The fallopian tubes are performing in such a manner that allows the released egg to meet with a sperm; and
  • Sperm can travel unhindered to the location of the egg, via the vagina, cervix, uterus, and fallopian tubes of the woman; and
  • The resultant fertilised egg is not hindered from the process of implantation in the uterus.

Female Reproductive System - Review

Female Reproductive System

Ovaries

The ovaries, found in the pelvis on either side of the uterus, are two almond-shaped organs. The functions of the ovaries are to produce eggs (also known as ova) and female sex hormones, oestrogen and progesterone. The ovaries contain a finite number of eggs, albeit in an immature form, meaning that all the eggs a woman can ever produce throughout her adult life exist from before birth.

Fallopian Tubes

The Fallopian tubes connect the ovaries to the uterus, acting as a tunnel for the eggs to travel through, following ovulation. The Fallopian tubes have small hair-like projections called cilia on the cells of the lining, which move the egg toward the uterus.

Damage may occur to the Fallopian tubes through infection, endometriosis, tumours, or scar tissue in the pelvis (also called pelvic adhesions). This may inhibit the journey of the egg to the uterus, or the journey of the sperm to meet the egg, reducing the probability of a successful fertilisation.  Sometimes an “ectopic pregnancy” may occur in a damaged Fallopian tube.

Uterus

The uterus (also known as the womb) is the hollow, pear-shaped organ located in the pelvis, which houses the developing foetus. The uterus comprises the cervix, (i.e., the lower part that opens into the vagina), and the corpus (i.e., the main body which will house the foetus). A small channel through the cervix allows sperm to enter and menstrual blood to exit.

Vagina

The vagina (also known as the birth canal) joins the cervix (as described above, the lower part of uterus) to the outside of the body.

The “Natural” Fertility Process – A Simple Explanation

What is fertilisation?

Fertilisation simply refers to the meeting of the male reproductive cell (i.e., the sperm) with the female reproductive cell (i.e., the egg). The product of fertilisation is called a zygote. The zygote will eventually develop into an embryo. Fertilisation is also commonly known as conception.

Where does fertilisation occur?

Fertilisation normally occurs at the end of the Fallopian tube, quite close to the ovary. The resulting fertilised egg (or zygote) travels down the tube, towards the uterus for implantation into the uterus wall. This journey usually takes around five days.

How do the sperm and egg meet?

During ovulation, the released egg is collected by the Fallopian tube, and moved down the tube. In the majority of cases of ovulation, a single egg is released.

Anywhere from 100 million to 300 million sperm are released in a single ejaculation, creating a “race” to the egg for those sperm. The sperm need to be the first to locate and penetrate the egg in order to be successful.

The cilia, within the Fallopian tubes, move to unite the successful sperm and egg, resulting in fertilisation.

What happen when sperm meets egg?

Shortly after the sperm penetrates the egg, it is “pulled inside”,  causing changes to the membrane of the egg, which inhibits other sperm from entering the egg.

What happens if fertilisation is successful?

Immediately following the successful fertilisation of an egg by a sperm, a zygote is formed. This is the initial stage of pregnancy and within twelve hours the first cell division has taken place.

The zygote continues its journey towards the uterus, through the Fallopian tube, until it is ready to implant into the wall of the uterus (about Day 4), where the zygote will receive nourishment and oxygen. At this time, the zygote becomes an embryo, which will continue to develop into a baby.

What happens if fertilisation doesn’t take place?

If there is no fertilisation or implantation, the egg will disintegrate and be absorbed. Hormone levels (i.e., oestrogen and progesterone) drop and the lining of the uterus (also called the endometrium) produces chemicals called prostaglandins, which cause the fragmentation of the endometrium, and stimulation of uterine contractions. A menstrual period sheds the endometrium through the cervix and vagina.