1. The male reproductive system
2. The female reproductive system
3. The female monthly cycle
4. Reproduction control
5. STD’s
6. Fertilization through embryonic development
7. Fetal development
8. Birth
9. Development after birth
1. Included in the male reproductive system are the testes, epididymides, vasa deferentia, seminal vesicles, prostate gland, urethra, bulbourethral glands and the penis. Sperm are produced in the testes and continue maturation in the epididymis. Mature sperm leave the epididymis and are stored in the vas deferens. The vas deferens drain into the ejaculatory duct which enters into the urethra. As seminal fluid is passed through the seminal vesicles, prostate gland, and bulbourethral glands, secretions are added to them and the liquid becomes what is known as semen that is excreted upon ejaculation. At the tip of the male penis is a swelling called the glans penis which at birth is covered by a layer of skin which is sometimes removed soon after birth. Nitric oxide is released during sexual arousal which allows for the release of cyclic guanosine monophosphate which allows for the erectile tissue to fill with blood thus becoming erect. In the time of an erection a sphincter cuts off the entrance from the bladder into the urethra so that no urine can enter. Semen enters the urethra after sexual arousal and contractions of the muscles in the penis push the semen out in spurts. Typically there is 3.5 ml of semen in one ejaculation and up to 400 million sperm in that 3.5 ml. the scrotum holds the testes a distance away from the body to allow for a lower temperature for the sperm to thrive in. if the temperature is too high, the sperm do not function properly. In the testes are seminiferous tubules which are the areas where sperm are produced. The production of sperm is done in the meiosis process which was discussed in an earlier chapter. A mature sperm is composed of three parts a head, middle piece and a tail. Movement of the tail is made possible by the energy producing mitochondria in the middle piece. In the head there are enzymes that are necessary to break through the egg during fertilization. Testosterone, the most important of the male sex hormones is secreted by the interstitial cells that lie between the seminiferous tubules. The hypothalamus regulates the secretion of the hormones that control production of sperm and testosterone. Testosterone brings about the changes in a mole during puberty such as broader shoulders, lower voice and hair on face, chest and back.
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2. The female reproductive system includes the ovaries, oviducts, uterus, cervix, and vagina along with various other organs. The ovaries are responsible for the production of eggs, estrogen and progesterone. The fallopian tubes are also known as the oviducts and they sweep the egg that has been expelled from the ovary into the tube. The egg moved down the tube toward the uterus. The uterus is the middle organ between the fallopian tubes and it ends with the cervix. The cervix opens into the vagina which is a canal for birth, allows for menstrual flow and is the sex organ in females. There are also external genitals on the female that are collectively known as the vulva. Upon sexual arousal some of the sexual organs become engorged with blood and lubrication seeps into the vagina.
3. The ovarian cycle has 6 stages first the primary follicle which contains an oocyte begins producing estrogen, and then the secondary follicle containing an oocyte also produces estrogen and progesterone. Third the vesicular follicle develops followed by ovulation. The fifth stage is when the oocyte has left the follicle; the follicle becomes a corpus luteum, which if unfertilized, will disintegrate. Estrogen is responsible for secondary sex characteristics in females such as fat distribution and hair growth. Later in a woman’s life the follicles slowly stop producing estrogen and progesterone ceasing the menstrual cycle, this change is known as menopause. These two hormones are also responsible for a series of events known as the uterine cycle. This cycle is divided by days. Days 1-5 the levels of the hormones cause blood vessels to rupture causing blood to seep from the vagina in a menstrual period. Days 6-13 there is a high production level of estrogen causes the endometrium to thicken. On day 14 ovulation typically occurs. days 15-28 production of progesterone increases and causes the endometrium of the uterus to increase in size and secrete a thick mucus preparing for implantation. If fertilization does not happen, the cycles begin again.
4. Regulation of the amount of children a person or a couple has is done in a variety of ways including the family planning method which has an 80% effectiveness rate, women’ s hormonal birth control which has between a 98% -99% effectiveness rate. The male condom has an 89% effectiveness rate. A diaphragm has a 90% effectiveness rate when used with a spermacide. IUD’s have a 99% effectiveness rate and contraceptive injections also have a 99% effectiveness rate. There is also a method of birth control used after intercourse to prevent fertilization, this is known as the morning after pill and has about an 80% effectiveness rate. Of all the birth control methods abstinence is obviously the safest and most effective in not only birth control but also STD protection.
5. Sexually transmitted diseases are caused by various factors including viruses, bacteria, protists, fungi and animals. STD’s caused by viruses include HIV which causes AIDS, genital warts, genital herpes, ad hepatitis. Of these STD’s there are only effective treatments for HIV/AIDS and genital herpes. Unfortunately though these are only treatments for the symptoms and do not cure the diseases. STD’s caused by bacteria are treatable and curable by use of antibiotics. These STD’s include Chlamydia, Gonorrhea, and syphilis. STD rates in America ire rising steadily and it is estimated that more than half of all people will have an STD at one time. (http://www.ashastd.org/learn/learn_statistics.cfm)
6. Sperm have long tails which allow them to swim toward the egg, once at the egg the head of the sperm releases a special enzyme that allows it to penetrate the egg then the sperm nucleus enters the egg and unites with the egg pronucleus and this is called fertilization. At this point the fertilized egg is known as a zygote. The zygote becomes an embryo and then a fetus. Lying outside the embryo and fetus are the extrambryonic membranes which are the chorion provides the fetus with nutrients and oxygen, the allantois protrudes from the embryo and collects the small amount of urine excreted form the fetal kidneys and will eventually form the bladder. The yolk sac is the first site of blood cell formation. The amnion contains fluid to cushion and protect the fetus during development. The gestation period is the 280 day period of time from the day of the start of the last menstruation to the day the baby is expected to be born. Pre-embryonic development is the first week of development beginning with fertilization of the egg followed by repeated division of cells while traveling down the oviduct to the uterus. A compact group of cells known as the morula becomes the blastocyst that arranges itself on a manner of an inner grouping of cells and an outer layer of cells. All the inner cells have the ability to develop into any type of tissue and will collectively become the embryo. Embryonic development begins in the second week and continues through the second month. During this time the embryo implants into the wall of the uterus and secretes the hormone human chorionic gonadotropin which is the hormone that is detected in pregnancy tests. In this week the inner cells become the embryonic disk and the yolk sac and the amniotic cavity form. During the third week of development the nervous system and the heart begin to develop. In the fourth and fifth weeks the umbilical cord develops and arms and legs develop from the limb buds. In the fifth week the head enlarges and the eyes ears and nose become visible. In the sixth through eighth weeks the form of the embryo begins to look more like a human being, the neck region develops and the nervous system is working enough to respond to stimuli. During the seventh week of development the gonads form and at this stage of development the male and female gonads look alike.
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7. The umbilical cord is the path of the fetal blood between the fetus and the placenta so that blood between the mother and child is rarely exchanged. During the third month the gender of the fetus can be distinguished, the head is large in proportion to the rest of the body. Also during the third and fourth months the cartilage begins to be replaced by bone and the baby’s heartbeat is easily distinguishable. In months five through seven the mother can feel the baby move and the baby’s eyelids are fully open. At the end of the seventh month the baby is about 12 inches long and weighs about 3 pounds. In the eighth through ninth months development finishes and the baby’s lungs further develop and he/she gains weight needed to survive outside the womb.
7. The umbilical cord is the path of the fetal blood between the fetus and the placenta so that blood between the mother and child is rarely exchanged. During the third month the gender of the fetus can be distinguished, the head is large in proportion to the rest of the body. Also during the third and fourth months the cartilage begins to be replaced by bone and the baby’s heartbeat is easily distinguishable. In months five through seven the mother can feel the baby move and the baby’s eyelids are fully open. At the end of the seventh month the baby is about 12 inches long and weighs about 3 pounds. In the eighth through ninth months development finishes and the baby’s lungs further develop and he/she gains weight needed to survive outside the womb.
8. There are three stages of labor, in stage one contractions pull the cervix up toward the baby’s head making the cervix virtually disappear, the water breaks and when the cervix is dialated completely the second stage begins. In stage two, contractions are about 1-2 minutes apart and last for 1 minute, the urge to push is becoming greater as the baby’s head lowers into the vagina. Once the head is delivered the rest of the body follows easily. In the third stage the placenta is delivered and the labor is complete.
9. Growth continues after birth in a sense all the way until death. As a person ages their body begins to show the signs such as the loss of skin elasticity, loss of movement in the joints, the cardiovascular system also suffers some signs of aging. Bone loss is also common later in life and many individuals suffer from osteoporosis. Tooth decay is also common in older individuals, but it is possible to prevent this with regular brushing and cleanings. It is inevitable that all humans will age and pass away, however it is possible to create a smooth transition by eating a healthy diet, exercising regularly and generally taking care of your body.
9. Growth continues after birth in a sense all the way until death. As a person ages their body begins to show the signs such as the loss of skin elasticity, loss of movement in the joints, the cardiovascular system also suffers some signs of aging. Bone loss is also common later in life and many individuals suffer from osteoporosis. Tooth decay is also common in older individuals, but it is possible to prevent this with regular brushing and cleanings. It is inevitable that all humans will age and pass away, however it is possible to create a smooth transition by eating a healthy diet, exercising regularly and generally taking care of your body.
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