Female Body

By understanding the reproductive process, one can understand that there are numerous places where the system may not work properly and thus result in infertility.

The female reproductive system consists of three main components:

  • Ovaries
  • Fallopian tubes
  • Uterus
Ovaries

Ovaries are small, oblong organs that are just below the fallopian tubes on each side of the uterus. The ovaries contain about 700,000 immature eggs; all the eggs that a woman will ever have are produced while she is still a fetus. Only a fraction of a woman’s eggs will ever develop into mature eggs during her lifetime. After puberty, many eggs will start the developmental process each month, however only one is usually released or ovulated each month. After the egg is released from the ovary it is picked up by the fallopian tube.

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Fallopian Tubes

Although the fallopian tube may appear to be a simple organ, it is in fact rather complex. Fertilization occurs in the fallopian tube. The tubes have fan-like ends called fimbriae that can sweep across the ovary and pick up the ovulated egg. During ovulation, the fimbriae create currents in the fluid inside the fallopian tube that help move the egg towards the uterus. The fallopian tubes sustain the female’s egg and male’s sperm throughout the fertilization process. It takes approximately seven days for the egg and the subsequently fertilized embryo to travel the length of the fallopian tube.

Fallopian tubes are responsible for:

  • Picking up a newly released egg
  • Transporting sperm to the egg
  • Sustaining an environment for fertilization
  • Moving a fertilized egg into the uterus

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Uterus

The uterus is the hollow, pear-shaped organ located in the low centre of a woman’s pelvis. The uterine lining, known as the endometrium, builds up during the proliferative phase of the menstrual cycle in anticipation of receiving a fertilized embryo from the fallopian tube. It protects, develops and nourishes the fetus until birth. If a woman is not pregnant, the uterine lining then sheds in the menstrual cycle.

The cervix is the connection between the vagina and the uterus. For intrauterine insemination or for embryo transfer, a catheter is passed through the vagina and through the cervical canal to reach the uterus. The cervix produces mucous secretions that change through the reproductive cycle. Around the time of ovulation the cervical mucous is thin and watery to aid in the passage of sperm to the uterus. After ovulation and/or during pregnancy, the mucous is thick to provide a barrier to the uterus from foreign material and infections.

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Normal Female Reproductive Physiology

Beginning at puberty, the body starts to make and release increasing amounts of follicle-stimulating hormone (FSH). This hormone, produced by the pituitary gland at the base of the brain, causes the follicles to grow and produce estrogen. The egg that is developing inside the follicle also begins to mature at this time. During the average menstrual cycle, around day 14, the pituitary gland releases a burst of another hormone called luteinizing hormone (LH); this is referred to as the LH surge. LH stimulates the final maturation of the egg and starts the ovulation process – resulting in the release of a mature egg from the follicle. As the egg travels through the fallopian tube, the ovulated follicle forms a cyst known as the corpus luteum, which produces levels of another female hormone, progesterone. Progesterone aids in the preparation of the uterine lining for the soon-to-be fertilized embryo.

If there are sperm present in the fallopian tube, the egg may be fertilized and the resulting embryo will pass through the fallopian tube and enter the uterus, where it will implant and hopefully grow into a baby. If the egg is not fertilized, the corpus luteum stays functional for approximately 10 days before beginning to disintegrate into scar tissue. 

If the egg is not fertilized, it will travel to the uterus. Approximately two weeks after ovulation the uterus then sends a signal to the ovary to decrease progesterone production since the womb is no longer needed that month and menstruation, or the shedding of the lining of the uterus, will follow. The menstrual cycle will begin anew to grow another egg for the next month.

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