Reproduction
from: http://www.sexualityandu.ca/teens/life-6.aspx
The Body and the Hormones
Most of us are equipped to have kids. Of course there are exceptions, for example when individuals suffer from certain diseases. In addition to organs like the liver, heart, and lungs, we have reproductive organs and we produce hormones inside our bodies. Hormones are courier substances that travel in the blood to carry messages from one organ to another. There are many different types of hormones. One group, sex hormones, controls the ability of women and men to reproduce.
The most important sex hormones in the female body are estrogen and progesterone. The male hormones are called androgens. The most important androgen is testosterone. It is not true that androgens are found only in males and estrogens are found only in females. Men carry female hormones and women carry male hormones as well.
Let’s look at the difference between the male and female reproductive organs. When choosing a method of contraception these “little” differences actually make a big difference.
The male
From the reproductive point of view the major differences between males and females are:
- Starting at puberty, men can make babies basically anytime provided they ejaculate.
- Sperm can stay alive in a woman’s reproductive organs for up to three days.
- Men are able to conceive children almost until the end of their lives.
- Men do not have a cycle to regulate fertility like women do.
- Men need to reach orgasm and ejaculate in order to reproduce.
The sperm production - How men produce babies
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There are internal (epididymis, vas deferens, prostate, urethra) and external reproductive organs (penis, scrotum holding the testicles or testes)
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Sperm production begins at the onset of puberty, at an average age of 13 years, and lasts throughout the life of a man. The sure sign for a young man that he is able to reproduce is that his erection is followed by an ejaculation. This is of course only “physically speaking”. Emotionally, you might be very far from being ready to take on the responsibility of becoming a father. Sperm, more precisely spermatozoa, are produced by the testicles, which are glands within the scrotum. The scrotum functions like a thermostat, regulating the temperature of the testicles. If you’re a male then you know that the scrotum becomes smaller and more wrinkled when you enter a cold pool. The scrotum contracts to bring the testicles closer to the body to keep them warm. The testicles produce hormones and sperm. Sperm production is an ongoing process. It takes about 70 days for one sperm to mature.
Let’s have a look at how sperm actually grow. At the beginning, sperm forms in the testicles, then travels through the epididymis. After that, the sperm reaches the vas deferens. It is stored there until ejaculation occurs. The prostate gland produces a liquid that helps sperm to survive after leaving the male body. During ejaculation, spermatozoa and liquid from the prostate and other glands make a mix while travelling through the urethra. This mix is called semen. The urethra is a tube that also connects to the bladder for passing urine. During sexual excitement, for example during lovemaking, this connection is interrupted so that the semen does not come into contact with urine. A sperm has the ability to swim and travel on its own. It has an oval-shaped head and a tail that serves as a propeller. Sperm carry the genetic information from the male and can unite with the female egg to produce an embryo. After two months, the embryo becomes a fetus, and later becomes a baby.
Survival of the fittest
Spermatozoa are very fragile and their chances of survival are very low. This is why the testicles of each individual produce millions of spermatozoa each day. The milky or creamy looking ejaculate consists of hundreds of millions of sperm, but only a few of them will survive the journey through the female vagina to the fallopian tube where the female egg is waiting to meet a sperm. Out of those few, only one will actually penetrate the egg and fertilize it.
Sperm, although it is very fragile, can also be very persistent. Occasionally pregnancy can occur without intercourse and even if the hymen is intact. The hymen is the membrane that partially covers the virgin vagina. This is called “splash pregnancy”. Sperm have been known to move very quickly from outside the vagina into the uterus. After intercourse sperm can survive up to three days in the reproductive organs of a female.
The female
Remember what we said earlier about the differences between the sexes? Here are the little differences that make up a female:
- The woman is able to have children from the time she begins to produce eggs (around 12 years) to the onset of menopause (around 52 years).
- The woman can conceive only during the three days (approximately) surrounding ovulation each month (2 days before and on the day of ovulation).
- The woman has a menstrual cycle that determines her fertility.
- The female egg can only be fertilized by male semen in a time period of 6-12 hours.
- The woman can become pregnant without being sexually aroused and reaching orgasm.
- The woman could be a virgin and still get pregnant (splash pregnancy).
Puberty: when hormones start working overtime
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The female body has internal and external reproductive organs. The exterior ones are: Mons pubis, clitoris, urethra, opening of the vagina (6-10 cm), inner and outer lips, and hymen. The interior organs are: cervix, uterus (womb), fallopian tubes (8-10 cm) and ovaries. The cervix is the entrance to the uterus
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Already at birth, the female body is equipped with a bank account of 300,000-400,000 egg cells, which are located in the ovaries. Of this large amount only 300-500 will be released during the reproductive years of a woman’s life. Starting between the ages of 8-10, hormone production rises and makes the body change from a girl to a young woman. The first menstruation, between ages 11-14, is the sure sign that the body is preparing to have children. This is of course only “physically speaking”. Emotionally, you might be very far from being ready to have children of your own.
Did You Know?
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25% of young women who have intercourse without using a method of birth control at any time during the cycle will become pregnant within one month.
85% will become pregnant within one year.
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From puberty on:
- The female produces one egg (ovulation) every month in the left or the right ovary.
- This egg is released to start its journey to the uterus through one of the fallopian tubes.
- The body prepares for a possible pregnancy.
Keep in mind that we’re talking about the usual stuff here. Of course there are exceptions such as the production of more than one egg, which might lead to two or more babies. This all happens due to the amazing teamwork between the hormones and organs. These things go on over and over again each month and this is what we call the female cycle.
The amazing female cycle
The cycle covers a time frame of 23-35 days. The average cycle lasts 28 days. The first day of the cycle is the first day of menstruation. The last day of the cycle is the last day before the following menstruation. Cycle lengths vary individually and they are not always regular. Stress, weight gain or weight loss, for example, can disturb it. After the first menstruation it may take 1-3 years until a woman gets a regular cycle.
During the first 14 days of the cycle (usually, but depending on cycle length) an egg is ripening. A hormone in the brain, which is called follicle stimulating hormone (FSH), stimulates the ripening process. The coat around the egg produces estrogen. This most important female hormone makes the lining of the uterus grow to form a nutritious and secure bedding for the egg to settle into after fertilization.
Approximately at day 14 of a 28-day cycle, an egg is ready to be released. Another hormone in the brain, which is called luteinizing hormone (LH), gives the impulse for the egg to emerge from the ovary and be taken up by the fallopian tube. This important event is called ovulation. This is also the most fertile time of the month for the woman to get pregnant. The egg then travels through the fallopian tube to the uterus. The journey takes about seven days. In the meantime, another important hormone produced in the ovary, progesterone, ispreparing the uterus for a pregnancy by securing a sufficient blood supply and by preventing the uterus from contracting and losing a fertilized egg.
Did You Know?
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In 2000, the fertility rate for adolescents (number of pregnancies per 1,000 women of reproductive age) was 17.3 compared with 33.9 for women in the 35-39 age group and 5.9 for women in the 40-44 age group. The highest abortion rates (number of abortions per 1,000 women) occur in women 18-19 years and 20-24 years of age.
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Sperm can fertilize the ready egg in the fallopian tube during a 6 to 12 hour period. Fertilization happens when a sperm enters the egg and the embryo starts to form. Two cells divide and become four, the four cells divide and become eight, and so on. By the time the cluster of cells reaches the uterus and settles down into the lining of the uterus, it has become an embryo. This settling down is called implantation. It takes about seven days from fertilization to implantation. The rise of estrogen and progesterone in the blood stream of the woman, along with the pregnancy hormone HCG from cells surrounding the embryo, signals pregnancy. From now on, the female body concentrates on the growth of the embryo and stops the cycle until a few weeks after the baby is born. This is why women cannot conceive again while they are pregnant. A woman can only have one pregnancy at a time, but this does not exclude the possibility of having more than one embryo or fetus at a time, e.g. twins.
The rise in estrogen and progesterone signals to the ovaries: Do not produce any more eggs for now. We have to take care of this embryo first! A pregnancy test can be positive 8-10 days after ovulation. If no fertilization of the egg occurs, the production of progesterone stops. So does the production of estrogens. The message is basically: We do not have a fertilized egg to produce an embryo this month, so stop all the preparations and start all over again! The end of the story is that the thickened lining of the uterus, which was supposed to be the bed for the fertilized egg, is no longer necessary. The same applies to the egg, which did not get fertilized. The body rids itself of this bedding and the egg by bleeding. This is known as the period or menstruation.
Did You Know?
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Did you know that a woman can become pregnant even...
...when she has intercourse for the first time?
...when she has her period?
...if she had no period yet?
...if her partner ejaculates not inside her vagina but close by?
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