The Female Reproductive System

Again, this system consists of organs which allows for the production of a new individual. The organs involved are the ovaries, fallopian tube, uterus, cervix and vagina.

The Ovaries

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  • They are approximately 3.5 cm in length and 2 cm wide and are located one on each side of the uterus, in the lateral walls of the pelvic cavity.
  • They are suspended by the ligaments in the upper pelvic cavity, one being on either side of the uterus. At the birth of a female, each ovary contains over 200,000 immature ova, with each ova being encased in a sac called a follicle. In response to various sex hormones, each follicle develops until they become primary follicles, which is when ovulation occurs.
  • The ovum breaks free of the follicle and enters the fallopian tube. The ovaries are also responsible for producing estrogen and progesterone, which are vital for proper reproductive function
  • There are two fallopian tubes, each about 4 inches in length and a narrow as a piece of string, attached to a side of the uterus. Each tube resembles a funnel, which is wider at the ovary and becomes narrower at the uterus.
  • Once in the fallopian tubes, Epithelial tissue that has tall, oblong-shaped cells with hair-like projections, known as ciliated columnar, move ova in one direction, down the narrow passageway towards the uterus.
  • If fertilization takes place, it will usually occur in the wider part of the fallopian tube. Once the ovum has become fertilized it is called a zygote and travels to the uterus over the next 7 days.

The Uterus

The uterus is suspended by broad ligaments and is situated between the bladder and the rectum. It is shaped like an upside-down pear, with a thick lining, muscular walls and a rich blood supply. It is made up of three layers, being the peritoneum (outer layer), myometrium (middle layer) and endometrium (inner lining). The uterus serves as a pathway for sperm to reach the fallopian tubes as well as to be able to expand and contract to accommodate a growing foetus and push the baby out during labour. If fertilisation occurs, the uterus will provide a source of attachment and nourishment for the growing zygote, which embeds into the endometrium. When a woman isn’t pregnant, the uterus is only about 3 inches long and 2 inches wide and the lining of the uterus (endometrium) breaks down during menstruation.

The Cervix

The uterus ends at the cervix which is the lower portion or neck of the uterus. The cervix is lined with mucus and joins the top end of the vagina. It is a thick tube of smooth muscle that acts as a channel for sperm to reach the waiting ovum. During late pregnancy, the walls of the narrowed channel thin out to allow for the baby’s head to descent. The opening of the cervix is very small and during childbirth, the cervix can expand to allow a baby to pass.

The Vagina

The vagina is the female’s sex organ and extends about 3 – 5 inches inside, up to the cervix. It is a muscular, ridged sheath connecting the external genitals to the uterus. The vagina acts as a pathway for the penis to enter during intercourse to allow sperm to be deposited. It also acts as a passageway for the birth of a baby. During sexual arousal, droplets of fluid appear along the vaginal walls and eventually cover the sides of the vagina completely. The tissues are rich in blood vessels which when engorged with blood as a result of sexual arousal, press against the tissue, forcing natural tissue fluids through the walls of the vagina

Menstruation, Conception and Pregnancy

Menstruation is controlled by hormones and the cycle is usually a 28-day process, although this can vary greatly.

  • During day 1 – 5 the hormones estrogen and progesterone reduce which causes a breakdown of the endometrium. This results in the discharge of blood, tissue fluid and mucus, but also in the preparation of a mature follicle.
  • During days 6 – 13, two more hormones, Follicle Stimulating Hormone (FSH) and luteinizing hormone stimulate the ovaries to produce more estrogen. This in turn allows for the endometrium to re-build.
  • By now a mature follicle is ready to be released on day 14.
  • Between days 15 – 28, progesterone is stimulated by luteinizing hormone to prepare the uterus to receive the fertilised ovum, if there is one.
  • If fertilisation does not occur, then the hormone changes will start the cycle over again and initiate the breakdown of the lining.

The process of conception is nothing short of a miracle. Once the ovum has been released, it travels along the fallopian tubes, producing an enzyme that attracts any sperm. One sperm will break through the tough coating of the ovum to fertilise it, which will then continue to the uterus. Once the zygote has arrived in the uterus it will implant itself into the endometrial lining and become an embryo.

Pregnancy

The first four weeks after fertilisation will show a rapid amount of development as all of the major organs and body systems start to develop. The placenta and umbilical cord, which sustains pregnancy, are also being formed.

  • During weeks 5 – 8, the embryo starts to become recognisably human in form as the limbs begin to grow and the torso straightens out.
  • By weeks 9 – 12, the first trimester is closing and the foetus is almost double in length with all organs formed. The eyelids are fused with the eyes remaining closed.
  • Weeks 13 – 16 see the foetus rapidly increasing in size, with movements alerting the pregnant women of its presence. The foetal circulation is now established with the blood being pumped around its body.
  • By the fifth month, the skin of the foetus has become more mature and a network of blood capillaries and nerve endings has become established.
  • The sixth month marks the end of the second trimester and the facial features are beginning to resemble those of a full-term baby. The growth rate is slow, but weight is being gained rapidly.
  • The last trimester up until 40 weeks is a period where the foetus continues to develop, but in a much smaller space.
  • By week 33, the foetus is still putting on weight at just over 5lb, but still lacks adequate fat stores under the skin.
  • The last few weeks of pregnancy can be a time of great discomfort for many women. For the foetus the fingernails have reached the ends of the digits and its body is covered in a coating called vernix. The average pregnancy lasts from 38 weeks from fertilisation or 40 weeks when calculated from the last day of the menstrual cycle.

Pathologies of the Reproductive System

DiseaseMeaning
MastitisInflammation of the breast tissue, which can be caused by infection, engorgement or blocked ducts.
AmenorrheaThe absence of menstruation in a woman who is still of a reproductive age.
DysmenorrheaPain during menstruation
EndometriosisSmall pieces of uterus lining are found outside of the uterus which causes pain.
Pelvic Inflammatory DiseaseInflammation of the uterus, fallopian tubes and ovaries.