Female Sex Hormones
Most hormones are released continuously from birth, but the amount produced fluctuates with the body’s needs. Hormones can either have a short-term effect as they do in the hourly fluctuating amounts of insulin that are released by the pancreas in response to blood-sugar levels. Alternatively they can have a long-term effect, such as in the extended activity of androgens on the sexual development of a woman’s body throughout the period of puberty. Estrogens and Progesterone are produced by the ovaries and undergo changes in level during a 28-day cycle. During pregnancy the placenta acts as an Endocrine organ, producing hormones to sustain the pregnancy and promote foetal growth.
Estrogens are female sex hormones that are created primarily in the ovaries. Estrogens control the progression of female sex characteristics. Estrogens also generate the re-enactment of the endometrium in readiness of a fertilized ovum. During pregnancy, high levels of estrogen are secreted, then a few days after childbirth the levels descend.
Progesterone is a sex hormone formed by the corpus luteum; it is produced from the remains of the Graafian follicle after the discharge of the ovum. Progesterone stimulates the endometrium to secrete a fluid, which shields and feeds the fertilized ovum in the uterus before implantation, until this function can be taken over by the placenta at the conclusion of the first trimester. After childbirth, the levels of progesterone plunge significantly. If the ovum is not fertilized at around day 26 of the menstrual cycle, the corpus luteum ceases to function. This instigates a prompt decline in progesterone development and brings about changes in the lining of the uterus, which leads to menstruation.
What does the Female Reproductive System do?
At birth a females ovaries contain 400,000 follicles, each one is made up of a collection of cells with an immature egg in its centre. During a lifetime, only a few hundred of these follicles will develop into mature eggs. Even before puberty the female reproductive system is active, producing hormones that play a role in the complex processes of female growth and development. During adolescence, increased hormonal activity involving the reproductive system as well as other endocrine organs results in the characteristic physical changes of puberty, which include breast enlargement, growth of pubic hair and the redistribution of body fat.
From around the age of 12 until around 50, the reproductive organs together with the endocrine system normally prepares a women’s body for a potential pregnancy each month. If conception occurs (sexual intercourse), the reproductive system will maintain the pregnancy for an average of 38 weeks, culminating in the birth of the baby.
If conception does not occur, the uterus lining prepared for an embryo is discharged during the period of the monthly bleeding (menstruation). The menstrual cycle takes place over a 28-day period:
Menstruation – the endometrium (lining of the uterus) stops working and is discharged.
Proliferative phase – replenishment of the endometrium takes place.
Ovulation – the ovum is released into the fallopian tube by the ovary.
Secretary phase – after ovulation, the ovum moves along the fallopian tube to the uterus, the lining of which has been thickened by hormones in preparation for a fertilized ovum. However, if the ovum is not fertilized, hormone levels drop and blood vessels in the uterus tauten.
- The menstrual cycle commences once more when the redundant eudiometrical blood and tissue is released from the body.
When menstrual periods stop this is called menopause, this marks the end of the reproductive years. The reproductive system slows down until it ceases to function.
Organs that make up the Female Reproductive System
A women’s reproductive system is usually thought of in terms of the pelvic organs. The proper functioning of these organs relies upon other parts of the body, especially the pituitary gland. The main organs involved are as follows:
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The Uterus (womb) is located low down in the abdominal cavity behind the bladder and in front of the rectum. The endometrium (uterus lining) is discarded monthly during menstruation. The top of the uterus is called the fundus and its base is called the cervix. In the centre of the cervix is the opening into the uterus, this expands when giving birth.
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The Ovaries are two small organs below the women’s waistline on either side of and a little below the fundus. The ovaries are held in place near the uterus by connective tissue and ligaments. These small organs create eggs and female sex hormones, together with oestrogen and progesterone (equally essential for reproduction).
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The Fallopian Tubes (also called oviducts) connects to the ovaries. Finger-like connecting tissues called fimbria wrap around the ovaries.
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The Vagina is the soft walled passage connected to the cervix. Persistent secretions lubricate the vagina and sustain acidity, which prevents infections. In the region of the opening of the vagina is the hymn.
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The External Genitals (vulva), consists of: the entrance to the vagina (introit us), the clitoris, the mons pubis, the labia minora and majora. The clitoris is the most sensitive part of the female gentile.
Reproduction
Male sperm and the female egg are brought together by sexual intercourse. The male inserts his penis into the female’s vagina and releases millions of sperm that swim towards the fallopian tubes of the female. If sexual intercourse occurs within 24 hours of ovulation the sperm may penetrate the egg, this is where fertilization takes place. The sperm’s nucleus fuses with the egg; the combined genetic material gives the blueprint for a new human being.
Conception
Conception is the time between fertilization and implantation. The fertilized egg passes along the fallopian tube and divides repeatedly to form a ball of cells called a conceptus. After seven days, the conceptus sinks into the uterus and becomes an embryo. If two cells separate when the fertilized egg first divides, the two cells will develop independently and result in identical twins. If two cells are released during ovulation and sperm fertilizes both, they will produce non-identical twins.
Pregnancy
Pregnancy is the time between conception and birth. For the first two months the developing baby is called an embryo. After this, once the baby’s organs are working, it is called a foetus. Amino acids surround and protect the foetus. The placenta keeps the baby alive and is attached to the uterus. Inside the placenta, food and oxygen pass from the mother’s blood to the foetus, and waste passes in the opposite direction. The umbilical cord carries blood between the placenta and the foetus.
Birth
At about 38 weeks after fertilization, the uterus starts to contract. This process is called labour and usually takes place 12 hours before the birth (but it can differ with each woman). Powerful contractions push the baby out through the vagina, and the baby takes it’s first breath of air.
If the baby is a girl, (as I have already mentioned in this report) at birth her ovaries will contain 400,000 follicles, each one will be made up of a collection of cells with an immature egg in its centre. She will be on her way to reproduce life – just as she has been reproduced.
Conclusion
Reproduction ensures that the human species does not become extinct. The male and female reproductive systems enable men and women to have children.
Bibliography
Grange Books, 2002, The Human Body Atlas, Grange Books
BMA, 2001, New guide to Medicines and Drugs, DK
Smart, 2001,The Concise Science Encyclopaedia, Kingfisher
Stoppard, 1996, Woman’s Body, DK
