Having talked about STDs, let me move on the the other important complication of premarital sex. That is of unwanted pregnancies. To prevent this, one must use contraceptives. Contraeptives are mechanisms, devices, or medications that are intended to reduce the likelihood of a sperm cell fertilizing the egg which will deliberately prevent or reduce the chances of pregnancy or childbirth. Effectiveness varies depending on method.
The methods are mainly:
Abstinence - simply means no sex, 100% effective
Birth Control Pill -They contain two hormones, an estrogen and a progestin. They work by stopping ovulation and by inhibiting the movement of sperm. Quite effective when used consistently
Cervical Cap -It is a small cap made of soft latex which is placed by a doctor up into her vagina and onto her cervix. Suction keeps the cap in place so sperm cannot enter the uterus. The woman can also put spermicide in the cap. Women should obtain a new cap yearly. 9% accidental pregnancy. Can also prevent STDs
Condom -(refer to last post).
Contraceptive Film/ suppositories -These are medications with a chemical that kills sperm (a chemical called nonoxynol-9). It is placed on or near the cervix (the opening of the womb). It dissolves in seconds. Quite ineffective and does not work against STDs.
Contraceptive Sponge -It acts as a barrier to prevent semen from entering the cervix. Ineffective, but can prevent STDs because it is a barrier.
Contraceptive Implant -Implanon is an implant inserted into the upper arm. They give off small amounts of a hormone like the progesterone that stops the releasing of the egg. This effectively prevents pregnancy (but not STDs) for 3 years.
Diaphragm - It is a latex disc a woman places into her vagina. It blocks a man's semen from entering the cervix (the opening to the womb). A spermicide placed onto the diaphragm kills sperm. Quite effective
Fertility Awareness Method(the "rhythm" method) -It is a understanding a woman's reproductive cycle by observing and writing down fertility signs that determine when she can become pregnant. The signs are then used to decide when best to have sex.
Injectable Contraception (most commonly known as Depo-Prevera) -A shot given every three months. It is provides a hormone like the progesterone that stops the woman's ovaries from releasing an egg and have other contraceptive effects. Very effective but no STD protection.
Intrauterine Contraception (IUD) -It is a small device which is placed into the uterine cavity. the IUD gives off copper into the uterine cavity which stops sperm from making their way up through the uterus. Very effective, inexpensive and can last for long time.
The Patch -It is a patch that can be pasted anywhere on the body. The hormones it gives out is like that of a pill and it has the same effect. Quite effective and can last for 7 days.
The Ring -NuvaRing is a small, flexible device that a woman inserts into her vagina once a month. The ring releases combined hormones (estrogen and progestin) to protect against pregnancy. Same effect as a pill.
Withdrawal -It is the act of a man pulling his penis out before ejaculation into the vagina. Not very effective as pre-ejaculate fluid can also contain semen.
So from today, I have researched through the various methods of contraceptions. Though different, we see that the methods require consistency to work. Couples should consult each other before deciding on their method to prevent unwanted pregnancies. Remember that no method (other than abstinence) is perfect.
I thank http://www.advocatesforyouth.org/youth/health/contraceptives for the info.
Monday, July 21, 2008
Saturday, July 19, 2008
Preventions and cures
According to http://microbiology.suite101.com/article.cfm/sti_and_std, the main ways to prevent STDs are Abstaining from sexual intercourse unless it is with a long-term monogamous relationship; Consistent, correct usage of latex condoms during sexual intercourse. You can also go for annual STD, such as chlamydia, testing which does not cure STDs, but give you an idea of whether you are infected so you can receive early treatment.
The first prevention need not be further explained. So I'll move on to the second. How do condoms work? A condom is a sheath made from latex, polyurethane, or lamb intestines which is designed to cover the penis, creating a barrier between sexual partners and thus preventing the exchange of bodily fluids, which include STDs and semen, between two sexual partners. This prevents partners to be infected with STDs and prevents the female from getting pregnant. Many condoms also include spermicide, to ensure that any semen which may escape will perish before it reaches an egg. Some companies also manufacture insertable female condoms that can be worn by female sexual partners. To use a condom properly, it must be put on in the beginning stages of sexual intercourse, because pre-ejaculate can still infect a partner or cause pregnancy. Roll the condom all the way down the shaft of the penis, adding lubricant to the outside if necessary. Make sure to use a water based, latex friendly lubricant. After ejaculation, the condom should be disposed of properly. In addition to using condoms correctly for maximum efficiency, it is also important to never use expired condoms. Ultimately, if used consistently, condoms shouldn't break and is 97% of the time effective.
So let me move on to the informative, rather than preventive measure, that on tests for STDs. Well, these tests are usually done as a blood, urine, cell or visual examination and there are different procedures for each infection. Some prominent ones include the HIV antibody test which involves a blood sample where doctors check for HIV antibodies. Sometimes, there will be a cervical swab (like a pap smear) like in Chlamydia and Trichomoniasis where doctors examine under the microscope for traces of the parasite or bacteria. Some tests like the one for Syphilis may even require collection of spinal fluid.
Done with prevention, let me move on to cures for STDs. Well, most STDs are relatively easy to cure. In fact, there have even been vaccines created like the one for HPV (genital warts). In most cases antibiotics can cure bacterial STDs. For example, to cure syphilis, a single intramuscular injection of penicillin, an antibiotic, is usually effective if the person has had syphilis for less than a year. Antibiotics are not, however, effective in fighting viral infections such as herpes and HIV. Instead, these viruses can be treated. For instance, HIV can be treated through the use of antiretroviral drugs. For Herpes, drugs, like acyclovir, work to hasten the healing of herpes sores and can also work to suppress an outbreak. However, the above drugs for viruses cannot prevent transmission and are not cures.
Thus the best way to protect oneself would still be protected sex or abstinence in general.
I thank http://www.epigee.org/health/std_testing.html and http://chirkut.blog.co.in/2008/06/23/how-do-condoms-work/ for the info.
The first prevention need not be further explained. So I'll move on to the second. How do condoms work? A condom is a sheath made from latex, polyurethane, or lamb intestines which is designed to cover the penis, creating a barrier between sexual partners and thus preventing the exchange of bodily fluids, which include STDs and semen, between two sexual partners. This prevents partners to be infected with STDs and prevents the female from getting pregnant. Many condoms also include spermicide, to ensure that any semen which may escape will perish before it reaches an egg. Some companies also manufacture insertable female condoms that can be worn by female sexual partners. To use a condom properly, it must be put on in the beginning stages of sexual intercourse, because pre-ejaculate can still infect a partner or cause pregnancy. Roll the condom all the way down the shaft of the penis, adding lubricant to the outside if necessary. Make sure to use a water based, latex friendly lubricant. After ejaculation, the condom should be disposed of properly. In addition to using condoms correctly for maximum efficiency, it is also important to never use expired condoms. Ultimately, if used consistently, condoms shouldn't break and is 97% of the time effective.
So let me move on to the informative, rather than preventive measure, that on tests for STDs. Well, these tests are usually done as a blood, urine, cell or visual examination and there are different procedures for each infection. Some prominent ones include the HIV antibody test which involves a blood sample where doctors check for HIV antibodies. Sometimes, there will be a cervical swab (like a pap smear) like in Chlamydia and Trichomoniasis where doctors examine under the microscope for traces of the parasite or bacteria. Some tests like the one for Syphilis may even require collection of spinal fluid.
Done with prevention, let me move on to cures for STDs. Well, most STDs are relatively easy to cure. In fact, there have even been vaccines created like the one for HPV (genital warts). In most cases antibiotics can cure bacterial STDs. For example, to cure syphilis, a single intramuscular injection of penicillin, an antibiotic, is usually effective if the person has had syphilis for less than a year. Antibiotics are not, however, effective in fighting viral infections such as herpes and HIV. Instead, these viruses can be treated. For instance, HIV can be treated through the use of antiretroviral drugs. For Herpes, drugs, like acyclovir, work to hasten the healing of herpes sores and can also work to suppress an outbreak. However, the above drugs for viruses cannot prevent transmission and are not cures.
Thus the best way to protect oneself would still be protected sex or abstinence in general.
I thank http://www.epigee.org/health/std_testing.html and http://chirkut.blog.co.in/2008/06/23/how-do-condoms-work/ for the info.
Friday, July 18, 2008
Premarital sex consequences
So, now we established that premarital sex is actually harmful, let us look at the practical remifications. Well, they include unwanted pregnancies and STDs, but today I will focus on the latter. Yes, admittedly, while STDs can be transmitted even with sex after marriage, we still must understand that at that stage, the couple is ready to accept the consequences of their action, do teens who participate in premarital sex do? Thus, STDs is a much more pressing issue on the uninformed teen who practises unprotected sex.
Well, STDs are diseases that are mainly passed from one person to another during oral, anal or vaginal sex. There are at least 25 different sexually transmitted diseases with a range of different symptoms. STD symptoms are soreness, unusual lumps or sores, itching, pain when urinating, and/or an unusual discharge from the genitals. STDs can also affect fetuses as the infection spreads through the placenta and cause problems like stillbirth or other complications.
As, I cannot talk about all the STDs, I will just touch on the more common ones today.
First up-Chlamydia. It is one of the most commonly reported bacterial sexually transmitted diseases. It is caused by the Chlamydia trachomatis bacterium. It infects the urethra, rectum and eyes in both sexes, and the cervix in women. If left untreated, long-term infection can lead to fertility problems in women.
Next-Pubic Lice. They are small crab-shaped parasites that burrow into the skin to feed on blood. They live on coarse body hair, predominantly pubic hair. The lice use their crab-like claws to grip hair strands.
Next-Genital warts. They are caused by some sub-types of Human Papillomavirus (HPV). They can appear on the skin anywhere in the genital area as small whitish or flesh-coloured bumps. They are unlikely to cause pain but may itch and can be difficult to spot.
Next-Gonorrhea. It is an infection that can infect the urethra, cervix, rectum, anus and throat. Symptoms include a burning sensation when urinating and abnormal discharges from genitals or the anus.
Next-Herpes. It is caused by two strains of the herpes simplex virus, type 1 (HSV-1) and type 2 (HSV-2). HSV-2 is more common and usually manifests itself in the genital and anal area. Symptoms include blisters, itching sensations and flu-like symptoms.
Next-Molluscum contagiosum (also known as water warts). It is a common viral infection resulting in a skin disease that presents itself as small bumps, often in clusters. They are filled with a gungy white fluid that is very contagious. The bumps usually appear on exposed skin such as the torso, thighs, genitalia and anus.
Next-Scabies. It is an intensely itchy, contagious skin infestation of the parasitic mite Sarcoptes scabiei. Female mites burrow into the outer layer of the skin (stratum croneum) to lay eggs. This causes intense itching
Next-Syphilis. It is a bacterial infection caused by Treponema pallidium. Symptoms include ulcers and flu-like symptoms. If left untreated, it can affect organs like the heart.
Next-Trichomoniasis (also known as Trich). It is caused by the single-celled organism Trichomonas vaginalis, which is transmitted through sex. It can infect the vagina and the male and female urethra. Often this STD presents no visible symptoms.
Next-HIV (human immunodeficiency virus). It is a virus that kills your body’s "CD4 cells." CD4 cells (also called T-helper cells) help your body fight off infection and disease. This leads to another disease called AIDS. There is no cure to HIV and symptoms are hard to detect.Next-Hepatitis B. It is a virus attacks your liver. It can cause permanent damage and even liver cancer.
Having shown you the dire consequence one can have from unprotected premarital sex. I will show you later ways to prevent it.
I would like to thank avert.org and http://www.pamf.org/teen/sex/std/ for the information.
Well, STDs are diseases that are mainly passed from one person to another during oral, anal or vaginal sex. There are at least 25 different sexually transmitted diseases with a range of different symptoms. STD symptoms are soreness, unusual lumps or sores, itching, pain when urinating, and/or an unusual discharge from the genitals. STDs can also affect fetuses as the infection spreads through the placenta and cause problems like stillbirth or other complications.
As, I cannot talk about all the STDs, I will just touch on the more common ones today.
First up-Chlamydia. It is one of the most commonly reported bacterial sexually transmitted diseases. It is caused by the Chlamydia trachomatis bacterium. It infects the urethra, rectum and eyes in both sexes, and the cervix in women. If left untreated, long-term infection can lead to fertility problems in women.
Next-Pubic Lice. They are small crab-shaped parasites that burrow into the skin to feed on blood. They live on coarse body hair, predominantly pubic hair. The lice use their crab-like claws to grip hair strands.
Next-Genital warts. They are caused by some sub-types of Human Papillomavirus (HPV). They can appear on the skin anywhere in the genital area as small whitish or flesh-coloured bumps. They are unlikely to cause pain but may itch and can be difficult to spot.
Next-Gonorrhea. It is an infection that can infect the urethra, cervix, rectum, anus and throat. Symptoms include a burning sensation when urinating and abnormal discharges from genitals or the anus.
Next-Herpes. It is caused by two strains of the herpes simplex virus, type 1 (HSV-1) and type 2 (HSV-2). HSV-2 is more common and usually manifests itself in the genital and anal area. Symptoms include blisters, itching sensations and flu-like symptoms.
Next-Molluscum contagiosum (also known as water warts). It is a common viral infection resulting in a skin disease that presents itself as small bumps, often in clusters. They are filled with a gungy white fluid that is very contagious. The bumps usually appear on exposed skin such as the torso, thighs, genitalia and anus.
Next-Scabies. It is an intensely itchy, contagious skin infestation of the parasitic mite Sarcoptes scabiei. Female mites burrow into the outer layer of the skin (stratum croneum) to lay eggs. This causes intense itching
Next-Syphilis. It is a bacterial infection caused by Treponema pallidium. Symptoms include ulcers and flu-like symptoms. If left untreated, it can affect organs like the heart.
Next-Trichomoniasis (also known as Trich). It is caused by the single-celled organism Trichomonas vaginalis, which is transmitted through sex. It can infect the vagina and the male and female urethra. Often this STD presents no visible symptoms.
Next-HIV (human immunodeficiency virus). It is a virus that kills your body’s "CD4 cells." CD4 cells (also called T-helper cells) help your body fight off infection and disease. This leads to another disease called AIDS. There is no cure to HIV and symptoms are hard to detect.Next-Hepatitis B. It is a virus attacks your liver. It can cause permanent damage and even liver cancer.
Having shown you the dire consequence one can have from unprotected premarital sex. I will show you later ways to prevent it.
I would like to thank avert.org and http://www.pamf.org/teen/sex/std/ for the information.
Wednesday, July 16, 2008
Premarital sex ban
At first, I wanted to write about benefits about premarital sex, but I realised very few people truly believe premarital sex is right, they just do it for impulse and curiousity. Then they regret it. But if there is such a consensus, why isn't the government banning it?
The biggest argument that is stopping a ban of premarital sex in liberal democracies today is the fact that people have freedom of choice and that if they want to engage in sexual acts, they should know the consequences, accept it and the government should not intervene. In fact if the government intervenes, the people may feel their rights infringed and may rebel even more, since it is impossible to suppress curiousity, which drives premarital sex.
But then again, if the government does not ban it, is it right? That is a weird question as many people view the government as a moral beacon and model. The message it sends when it does not ban premarital sex seems to lean towards the advocation of it. Yet, if we take a step back and look at the numeroues health campaigns, sex education classes that the government has sponsored, we ask ourselves, maybe even the government is against such acts. The thing is, the government cannot make a firm decision on whether or not this is right or wrong because society has evolved so much that the current day trend is as influential as religion, thus, if any law were to be passed, we would disatisfy the people and the trend.
So the government is hindered in deciding what is right or wrong because it is accountable to the people. They have left premarital sex in a very debatable grey area. Thus, it is up to you to decide. Do you want to have premarital sex? Are you ready for it? Do you want to follow the crowd? Ultimately, no one can decide for you, only yourself.
The biggest argument that is stopping a ban of premarital sex in liberal democracies today is the fact that people have freedom of choice and that if they want to engage in sexual acts, they should know the consequences, accept it and the government should not intervene. In fact if the government intervenes, the people may feel their rights infringed and may rebel even more, since it is impossible to suppress curiousity, which drives premarital sex.
But then again, if the government does not ban it, is it right? That is a weird question as many people view the government as a moral beacon and model. The message it sends when it does not ban premarital sex seems to lean towards the advocation of it. Yet, if we take a step back and look at the numeroues health campaigns, sex education classes that the government has sponsored, we ask ourselves, maybe even the government is against such acts. The thing is, the government cannot make a firm decision on whether or not this is right or wrong because society has evolved so much that the current day trend is as influential as religion, thus, if any law were to be passed, we would disatisfy the people and the trend.
So the government is hindered in deciding what is right or wrong because it is accountable to the people. They have left premarital sex in a very debatable grey area. Thus, it is up to you to decide. Do you want to have premarital sex? Are you ready for it? Do you want to follow the crowd? Ultimately, no one can decide for you, only yourself.
Monday, July 14, 2008
premarital sex
Now that we have answered the first question (how is reproduction possible?), let us move on to the second on issues on sex - Is premarital sex right or wrong and what are its consequences?
Now this is a prominent issue, according to the 1974 National Survey data in US, adults, 25 years of age, 97% of men and 81% of women had premarital sex. Thus addressing it should prove important and beneficial.
Well, right now, I will discuss why it may be wrong. Now in a moral perspective, religion has always looked down on premarital sex. The Bible refers to premarital sex as fornication. Premarital sex is just as much of a sin as adultery and all other forms of sexual immorality. They all involve having sexual relations with someone you are not married to. Most people believe that something sacred like virginity should be kept for the person you truly love. Sadly, most youths in fact have sex based on impulse and emotions. They do it out of peer pressure, curiousity and recreation, rather than love. This is because they have not matured. Thus, morally it is incorrect.
But deeper in, practical remifications of premarital are also plentiful. Firstly, the youth is unprepared for a deep relationship so should anything happen, like unwanted pregnancies, the youths will not be able to support each other. Even if they do love each other, their age will hinder them as they cannot earn a living to support their family, thus abortions usually occur. Other than that, premarital sex usually cause the couple to feel guilty and depressed after the act and this affects their emotional health. This is because they never truly loved each other and is regretful. Lastly, chances of gainng STDs is also high as much premarital sex is on impulse so most people don't know about the health condition of their partners.
But ultimately, do these problems deter society from having premarital sex? Why not? I will elaborate further.
Now this is a prominent issue, according to the 1974 National Survey data in US, adults, 25 years of age, 97% of men and 81% of women had premarital sex. Thus addressing it should prove important and beneficial.
Well, right now, I will discuss why it may be wrong. Now in a moral perspective, religion has always looked down on premarital sex. The Bible refers to premarital sex as fornication. Premarital sex is just as much of a sin as adultery and all other forms of sexual immorality. They all involve having sexual relations with someone you are not married to. Most people believe that something sacred like virginity should be kept for the person you truly love. Sadly, most youths in fact have sex based on impulse and emotions. They do it out of peer pressure, curiousity and recreation, rather than love. This is because they have not matured. Thus, morally it is incorrect.
But deeper in, practical remifications of premarital are also plentiful. Firstly, the youth is unprepared for a deep relationship so should anything happen, like unwanted pregnancies, the youths will not be able to support each other. Even if they do love each other, their age will hinder them as they cannot earn a living to support their family, thus abortions usually occur. Other than that, premarital sex usually cause the couple to feel guilty and depressed after the act and this affects their emotional health. This is because they never truly loved each other and is regretful. Lastly, chances of gainng STDs is also high as much premarital sex is on impulse so most people don't know about the health condition of their partners.
But ultimately, do these problems deter society from having premarital sex? Why not? I will elaborate further.
Friday, July 11, 2008
Pregnancy
So after going through fertilisation, let us look more in depth into pregnancy (also known as gestation). Well, Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. Childbirth usually occurs about 38 weeks from fertilization. Pregnancy is typically broken into three periods, or trimesters, each of about three months. While there are no hard and fast rules, these distinctions are useful in describing the changes that take place over time.
The beginning of pregnancy may be detected in a number of ways, including various pregnancy tests which detect hormones generated by the newly-formed placenta. The tests are known as Human Chorionic Gonadotrophin (HCG). Clinical blood and urine tests can detect pregnancy soon after implantation, which is as early as 6-8 days after fertilization. The tests are usually carried out on the day where a woman's monthly menstruation period is due.
After fertilisation and during the first trimester, the developing embryo becomes implanted into the endometrial lining of a woman's uterus. The embryo is a blastocyst which secretes a hormone named human chorionic gonadotropin which in turn, stimulates the corpus luteum in the woman's ovary to continue producing progesterone. This acts to maintain the lining of the uterus so that the embryo will continue to be nourished. The glands in the lining of the uterus will swell in response to the blastocyst, and capillaries will be stimulated to grow in that region. This allows the blastocyst to receive vital nutrients from the woman. During this time, the fetus is still developing by division via mitosis in the female
Months 4 through 6 of the pregnancy are called the second trimester. Most women feel more energized in this period. Although the fetus begins moving and takes a recognizable human shape during the first trimester, it is not until the second trimester that movement of the fetus, can be felt. The placenta is now fully functioning and the fetus is making insulin and urinating. The teeth are now formed inside the fetus's gums and the reproductive organs can be recognized, and can distinguish the fetus as male or female.
In the third trimester, movement of the fetus becomes stronger and more frequent and via improved brain, eye, and muscle function the fetus is prepared for ex utero viability. The woman can feel the fetus "rolling" and it may cause pain or discomfort when it is near the woman's ribs and spine. This period of her pregnancy can be uncomfortable, causing symptoms like weak bladder control and back-ache. It is also during this time that a baby born prematurely may survive.
I thank wikipedia again for the information.
The beginning of pregnancy may be detected in a number of ways, including various pregnancy tests which detect hormones generated by the newly-formed placenta. The tests are known as Human Chorionic Gonadotrophin (HCG). Clinical blood and urine tests can detect pregnancy soon after implantation, which is as early as 6-8 days after fertilization. The tests are usually carried out on the day where a woman's monthly menstruation period is due.
After fertilisation and during the first trimester, the developing embryo becomes implanted into the endometrial lining of a woman's uterus. The embryo is a blastocyst which secretes a hormone named human chorionic gonadotropin which in turn, stimulates the corpus luteum in the woman's ovary to continue producing progesterone. This acts to maintain the lining of the uterus so that the embryo will continue to be nourished. The glands in the lining of the uterus will swell in response to the blastocyst, and capillaries will be stimulated to grow in that region. This allows the blastocyst to receive vital nutrients from the woman. During this time, the fetus is still developing by division via mitosis in the female
Months 4 through 6 of the pregnancy are called the second trimester. Most women feel more energized in this period. Although the fetus begins moving and takes a recognizable human shape during the first trimester, it is not until the second trimester that movement of the fetus, can be felt. The placenta is now fully functioning and the fetus is making insulin and urinating. The teeth are now formed inside the fetus's gums and the reproductive organs can be recognized, and can distinguish the fetus as male or female.
In the third trimester, movement of the fetus becomes stronger and more frequent and via improved brain, eye, and muscle function the fetus is prepared for ex utero viability. The woman can feel the fetus "rolling" and it may cause pain or discomfort when it is near the woman's ribs and spine. This period of her pregnancy can be uncomfortable, causing symptoms like weak bladder control and back-ache. It is also during this time that a baby born prematurely may survive.
I thank wikipedia again for the information.
Wednesday, July 9, 2008
Fertilisation
So now that we have covered how the sperms and eggs prepare for fertilisation, let us go in depth on how fertilisation actually takes place. So firstly, sexual intercourse must take place and the male must ejaculate sperms into the female's vagina. As ovulation approaches, the cervical mucus becomes watery allowing the sperm to swim up the vagina through the cervix. Only about 2,000 sperm will be strong enough to reach the uterus and the fallopian tube.
So to begin, sperms must penetrate the cell membrane of the oocyte. To reach the oocyte, the sperm must pass through the corona radiata and the zona pellucida; two layers covering and protecting the oocyte from fertilization by more than one sperm. When the sperm reaches the zona pellucida, which is an extra-cellular matrix of glyco-proteins, a special complementary molecule on the surface of the sperm head then binds to a ZP3 glyco-protein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida.
When the sperm penetrates the zona pellucida, the cortical reaction occurs. Cortical granules inside the secondary oocyte fuses with the plasma membrane of the cell, causing enzymes inside these granules to be expelled by exocytosis to the zona pellucida. This in turn causes the glyco-proteins in the zona pellucida to cross-link with each other, making the whole matrix hard and impermeable to sperm. This prevents fertilization of an egg by more than one sperm.
So with the fusion of cell membranes of the sperm and opcyte, both the oocyte and the sperm also go through transformations, preparing for the fusion of their genetic material.
For the oocyte, it completes its second meiotic division. This results in a mature ovum. The nucleus of the oocyte is called a pronucleus in this process, to distinguish it from the nuclei that are the result of fertilization.
The sperm's tail and mitochondria degenerate with the formation of the male pronucleus. This is why all mitochondria in humans are of maternal origin.
The pronuclei migrate toward the center of the oocyte, rapidly replicating their DNA as they do so to prepare the new human for its first mitotic division.
The male and female pronuclei don't fuse, although their genetic material do so. Instead, their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms around them to catch the chromosomes before they get lost in the egg cytoplasm. By subsequently performing a mitosis, the cell gathers genetic material from the male and female together. Thus, the first mitosis of the union of sperm and oocyte is the actual fusion of their chromosomes.
Each of the two daughter cells resulting from that mitosis have one replica of each chromatid that was replicated in the previous stage. Thus, they are genetically identical. These cells will continue to divide so the fetus can develop
I thank wikipedia for the information and pictures.
So to begin, sperms must penetrate the cell membrane of the oocyte. To reach the oocyte, the sperm must pass through the corona radiata and the zona pellucida; two layers covering and protecting the oocyte from fertilization by more than one sperm. When the sperm reaches the zona pellucida, which is an extra-cellular matrix of glyco-proteins, a special complementary molecule on the surface of the sperm head then binds to a ZP3 glyco-protein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida.
When the sperm penetrates the zona pellucida, the cortical reaction occurs. Cortical granules inside the secondary oocyte fuses with the plasma membrane of the cell, causing enzymes inside these granules to be expelled by exocytosis to the zona pellucida. This in turn causes the glyco-proteins in the zona pellucida to cross-link with each other, making the whole matrix hard and impermeable to sperm. This prevents fertilization of an egg by more than one sperm.
So with the fusion of cell membranes of the sperm and opcyte, both the oocyte and the sperm also go through transformations, preparing for the fusion of their genetic material.
For the oocyte, it completes its second meiotic division. This results in a mature ovum. The nucleus of the oocyte is called a pronucleus in this process, to distinguish it from the nuclei that are the result of fertilization.
The sperm's tail and mitochondria degenerate with the formation of the male pronucleus. This is why all mitochondria in humans are of maternal origin.
The pronuclei migrate toward the center of the oocyte, rapidly replicating their DNA as they do so to prepare the new human for its first mitotic division.
The male and female pronuclei don't fuse, although their genetic material do so. Instead, their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms around them to catch the chromosomes before they get lost in the egg cytoplasm. By subsequently performing a mitosis, the cell gathers genetic material from the male and female together. Thus, the first mitosis of the union of sperm and oocyte is the actual fusion of their chromosomes.
Each of the two daughter cells resulting from that mitosis have one replica of each chromatid that was replicated in the previous stage. Thus, they are genetically identical. These cells will continue to divide so the fetus can develop
I thank wikipedia for the information and pictures.
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