1. Human Life Cycle
2. Meiosis again--eggs and sperm
3. Male reproductive organs
4. Female reproductive organs
5. Birth Control
6. STD’s
7. Infections
8. Fetal Development and Birth
1. Human Life Cycle
The human life cycle starts with meiosis goes through fertilization, fetal development, birth, childhood and adolescence, Adulthood, Aging and finally death. Each stage has particular biological significance to the body; it’s operation and appearance.
2. Meiosis, eggs and sperm
Meiosis is when the chromosomes from each organism are chosen for the new organism.
a. Meiosis in the male organs
In the male this happens in the tissue of the testes, which are full of seminiferous tubules, which is where sperm is created. The stem cells are always undergoing meiosis in the walls of the tubules. The sperm is collected in the epididymis. According to http://www.andrologyaustralia.org/pageContent.asp?pageCode=MALEREPROD#MALEREPRODEPI, “The epididymis is a highly coiled tube (duct) that lies at the back of the testes and connects the seminiferous tubules in the testis to another single tube called the vas deferens. The epididymis is about 5 meters long if stretched out. All sperm must pass through the epididymis when they leave the testis. When released from the testis, the sperm spend two to 10 days passing through the epididymis. During this journey, the sperm mature and gain the ability to move (swim or become motile).” The sperm that doesn’t get used goes back into the testicular tissue.
b. Meiosis in the female organs
Meiosis in females occurs in the ovaries. There are two phases, the first happens in the fetal ovary. The first phase isn’t one we often think about, it occurs when the one egg matures and breaks free from the wall of the ovary to be taken up into the fallopian tube, which happens during the menstrual cycle during ovulation. Phase two happens when the egg is fertilized.
3. Male reproductive organs
The sperm is made in the testes and carried by the vas deferens. The vas deferens is the helpful tubes that carry the sperm into the urethra to prepare for ejaculation. The semen is made by the seminal glands that are located at the base of the penis and in the prostate.
a. Vasectomy
In a vasectomy a small part of the vas deferens is cut out so that the sperm can’t get to the urethra for ejaculation. Everything else stays the same, as before in relation to the production of the sperm, now all the sperm is unused and absorbed into the testicular fluid.
4. Female reproductive organs
The clitoris, is really the female penis, it is the same tissue that would have grown into a penis had the organism been a male. The bladder is located behind the pubis. The vagina is actually a muscular tube whose opening is located just behind the urethra. The Labia majorum is the tissue that surrounds and protects the vaginal opening, clitoris and urethra. The cervix is the part that the sperm has to get around to get through the fallopian tubes the to the eggs. The Oviducts are kind enough to get the eggs from the ovaries to the uterus. The ovaries are where the first parts of meiosis take place and are of course were eggs are produced.
5. Birth Control
There are many different types of birth control with different advantages and disadvantages. The most common are those that use hormones to trick the female body into thinking it is pregnant already and there for does not allow for an additional pregnancy. There hormone choices are things like the pill, the skin pact, the Depo-Provera shot, and the ring. Then there are condoms, which are available for male and female application. The male option is the most commonly used of those two options. Similar to condoms is the diaphragm and the sponge; these both use a barrier and spermicide like condoms. The ides is if the blockage doesn’t work the spermaside will kill, or mane the sperm to the point it can’t do it’s job. Spermaside can cause irritation to both the male and the female and increase the occurrence of bladder infection in females because the chemical in spermaside also kills the good bacteria in the vagina that protects the female from bladder infections. Then there are inserts like the IUD, or Intrauterine devices, which are inserted into the vagina. According to http://www.netdoctor.co.uk/sex_relationships/facts/contraceptivecoil.htm, “They sit in your womb and prevent you from getting pregnant. They do this in three main ways: they prevent your partner’s sperm from getting through your womb and into your tubes, they alter the secretions (mucus) in your cervix, creating a further barrier for sperm, they affect your womb lining – making it less likely to ‘accept’ an egg.” There are also the permanent options of a vasectomy for the man, which I previously discussed, and for women a tubal ligation or essure. A tubal ligation is when the fallopian tube is tied, or sometimes-clipped shut so the sperm cannot get to the egg. Essure works in a similar way, a coil is inserted into the fallopian tube through the vagina, inside of the coil is a tissue growth stimulator, after 3 to 6 months tissue grows and blocks the fallopian tube.
6. STD’s
Sexually transmitted diseases are a rising problem. Viral STD’s can’t be treated with antibiotics, but some can be treated by a smaller selection of antiviral. These include; HIV, genital warts, genital herpes and hepatitis. There are also bacterial STD’s that can be treated with antibiotics; those include Chlamydia, Gonorrhea, and Syphilis.
a. Hepatitis
Hepatitis is an infection of the liver. There are six types, A, B, C, D, E and G. As far as STD’s go type B is the most common and is transmitted through sexual contact or through contaminated blood. It can lead to the liver failing. There is a vaccine that can be injected for protection against types A and B.
b. STD prevention
There are some things that can help prevent STD infection. Obviously is you don’t have sex it won’t be a problem. Reducing the number of partners and staying in long term relationships reduce ones changes of contraction. Partners need to be honest with each other about STD’s. And using condoms can help to prevent the spread of STD’s.
7. Infections
The reproductive track can be prone to several different types of infections. First Bacterial vaginosis or BV happens when there’s a disruption of the natural floras in the vagina and causes overgrowth of a certain bacteria. BV is responsible for 50 percent of vaginitis (infection of the vagina) in American women. Trichomoniasis is caused by protozoan (single celled eukaryotic organisms that like to be around moisture and cause many diseases). This can lead to vaginitis and causes a thick discharge, bad smell and itching. Candidiasis is a condition where there is too much yeast in the vagina. It can be caused by hormones in birth control and antibiotics. Common symptoms are red skin, inflammation, itching and white thick discharge.
8. Fetal Development and Birth
a. Fertilization and Implantation
In this first stage about a week into development mitosis is created smaller cells.
This is also called ectopic pregnancy because the fertilized egg implants.
b. Early embryonic development
The plan for the body is ready to go. The fetus is still very small, no organs have formed yet but the placenta is developing.
c. From fetus to adult
The body becomes an adult structure. The adult body has the following attributes from early on in the fetal stages: guts, brain and spinal cord, muscles and bones.
d. The Changes in the female body during pregnancy
Pregnancy is very disruptive to the female body it can cause the bladder and rectum to squeeze tightly. The stomach gets pushed on and becomes smaller requiring more frequent small meals instead of large ones. Also the immune system will respond differently and change the appetite of the mother so poisons don’t make there way to the fetus. The posture has to change because of the increased weight and mass the pregnancy creates. And of course the breasts get larger to allow for milk production.
e. Birth
Birthing can be approached many different ways. In America the hospital birth is common, but in other regions home births are more common. I was born at home; it was just dad and I my mom.
Sources: http://www.contexo.info/DNA_Basics/Meiosis.htm, http://www.bio-medicine.org/biology-dictionary/Seminiferous_tubules/, http://daphne.palomar.edu/psycsoc125/HSClass/anatomy_ts/pages/m_anat.html http://www.andrologyaustralia.org/pageContent.asp?pageCode=MALEREPROD#MALEREPRODEPI, http://www.netdoctor.co.uk/sex_relationships/facts/contraceptivecoil.htm, Frolich PowerPoint for cells and Human Biology 10th edition, Human Biology 10th
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