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Chapter 18 Answers: Reproductive System
18.2 Introduction to the Reproductive System: Review Questions and Answers
What is the reproductive system? The reproductive system is the organ system responsible for the production and fertilization of gametes and, in females, the carrying of a fetus.
Explain the difference between the vulva and the vagina. The vagina is a specific internal tract in females that connects the uterus to the outside of the body. The vulva refers to all of the external structures of the female reproductive system, including the clitoris, labia, and openings of the urethra and vagina.
18.3 Structures of the Male Reproductive System: Review Questions and Answers
Describe the structure of a testis. The testes are filled with hundreds of tiny, tightly coiled seminiferous tubules, where sperm are produced. The tubules contain sperm in different stages of development and also Sertoli cells, which secrete substances needed for sperm production. Between the tubules are Leydig cells, which secrete testosterone.
Which parts of the male reproductive system are connected by the ejaculatory ducts? What fluids enter and leave the ejaculatory ducts? The paired ejaculatory ducts form where the vas deferens join with the ducts of the seminal vesicles in the prostate gland. The ejaculatory ducts connect the vas deferens with the urethra. Sperm enter the ejaculatory ducts from the vas deferens, glandular secretions enter the ejaculatory ducts from seminal vesicles and prostate gland. The resulting fluid is semen, which leaves the ejaculatory ducts and enters the urethra during ejaculation.
A vasectomy is a form of birth control for men that is performed by surgically cutting or blocking the vas deferens so that sperm cannot be ejaculated out of the body. Do you think men who have a vasectomy emit semen when they ejaculate? Why or why not? Men who have their vas deferens cut or blocked due to a vasectomy do emit semen when they ejaculate because the glands that produce semen, including the seminal vesicles, prostate, and bulbourethral glands, are still connected to the urethra. The semen will just lack sperm because the sperm will not be able to travel from the epididymis to the rest of the male reproductive tract.
18.4 Functions of the Male Reproductive System: Review Questions and Answers
Compare and contrast the terms: erection, ejaculation, and intromission. Erection usually occurs with sexual arousal as the columns of spongy tissue inside the penis become engorged with blood. Ejaculation is the process in which semen is propelled by peristalsis in the vas deferens and ejaculatory ducts from the urethra in the penis. Intromission is the event of depositing sperm in the female vagina. This requires the penis to become stiff and erect, a state referred to as an erection.
Describe semen and its components. Semen is a thick, whitish fluid that contains sperm and secretions from the seminal vesicles, prostate gland, and bulbourethral glands. These secretions are important for sperm survival and motility.
Explain how erection occurs. Erection usually occurs with sexual arousal as the columns of spongy tissue inside the penis become engorged with blood.
18.5 Disorders of the Male Reproductive System: Review Questions and Answers
Identify some of the underlying causes of erectile dysfunction. Discuss types of treatment for erectile dysfunction. Erectile dysfunction is a disorder characterized by the regular and repeated inability of a sexually mature male to obtain and maintain an erection. Erectile dysfunction occurs when normal blood flow to the penis is disturbed or there are problems with the nervous control of penile engorgement or arousal.
Identify possible treatments for epididymitis. Why is treatment important, even when there are no symptoms? Treatments for epididymitis may include antibiotics, anti-inflammatory drugs, and painkillers. Treatment is important, even when there are no symptoms, in order to prevent the possible spread of infection, permanent damage to the epididymis or testes, and infertility.
What are some of the symptoms of prostate cancer? List risk factors for prostate cancer. How is prostate cancer detected? Prostate cancer is the most common type of cancer in men and the second leading cause of cancer death in men. If there are symptoms, they typically involve urination, such as frequent or painful urination. Prostate cancer may be detected by a physical exam or a high level of prostate-specific antigen (PSA) in the blood, but a biopsy is required for a definitive diagnosis. Risk factors for prostate cancer include older age, family history, high-meat diet, and sedentary lifestyle, among others. In younger patients or those with faster-growing tumors, treatment is necessary and likely to include surgery to remove the prostate followed by chemotherapy and/or radiation therapy.
In many cases, treatment for prostate cancer is unnecessary. Why? When is treatment necessary, and what are treatment options? Prostate cancer is typically diagnosed relatively late in life and is usually slow growing, so no treatment may be necessary. In younger patients or those with faster-growing tumors, treatment is necessary and likely to include surgery to remove the prostate followed by chemotherapy and/or radiation therapy.
Testicular cancer is generally rare, but it is the most common cancer in one age group. What age group is it? Testicular cancer is the most common cancer in males between the ages of 20 and 39 years.
Identify possible signs and symptoms of testicular cancer. How can testicular cancer be diagnosed?Describe how testicular cancer is typically treated. A lump or swelling in one testis, fluid in the scrotum, and testicular pain or tenderness are possible signs and symptoms of testicular cancer. Testicular cancer can be diagnosed by a physical exam and diagnostic tests such as ultrasound or blood tests. Testicular cancer is typically treated with surgery to remove the affected testis, and this may be followed by radiation therapy and/or chemotherapy.
18.6 Structures the Female Reproductive System: Review Questions and Answers
State the general functions of the female reproductive system. The general functions of the female reproductive system are to produce haploid female gametes called eggs, secrete female sex hormones such as estrogen, provide a site for fertilization to occur, and carry and give birth to a fetus.
Describe the vagina and its reproductive functions. The vagina is an elastic, muscular canal that can accommodate the penis and is where sperm are usually ejaculated during sexual intercourse. The vagina is also the birth canal, through which a baby passes during childbirth. In addition, the vagina channels the flow of menstrual blood from the uterus.
Outline the structure and basic functions of the uterus. The uterus is a muscular organ above the vagina in the centre of the pelvis where a fetus develops. Its muscular walls contract to push out the fetus during childbirth. The cervix is the neck of the uterus that extends down into the vagina. It contains a canal connecting the vagina and uterus and through which sperm or an infant can pass.
What is the endometrium? How does it change during the monthly cycle? The endometrium is the innermost layer of the uterus. It thickens each month in preparation for an embryo but is shed in the following menstrual period if fertilization does not occur. If fertilization does occur, the endometrium is not shed but is maintained to nourish the embryo and develop into a maternal-fetal structure called the placenta.
Why are breasts included in discussions of reproduction, if they are not organs of the female reproductive system? Although the breasts are not organs of the reproductive system, they contain mammary glands that can produce milk to feed an infant after birth, so they are important for reproduction to be successful. Milk drains through ducts and sacs and out through the nipple when a baby sucks at the breast.
What is the function of the folds in the mucous membrane lining of the vagina? The folds in the mucous membrane lining of the vagina allow the vagina to widen and stretch in length. This allows it to accommodate the penis during intercourse and allows a baby to pass through it during childbirth.
What are two ways in which the female reproductive system protects itself from pathogens? Answers will vary. Sample answer: Two ways in which the female reproductive system protects itself from pathogens are: 1. the cervix can produce thick mucus to keep pathogens out of the uterus; 2. the pH in the vagina is normally acidic which keeps pathogens from colonizing it.
18.7 Functions of the Female Reproductive System: Review Questions and Answers
What is pregnancy, and what is the role of the maternal organism in pregnancy? Pregnancy is the carrying of one or more offspring from fertilization until birth. The maternal organism provides a protected environment for the offspring. She also provides all the nutrients and other substances needed by the offspring and removes its wastes.
What is the average duration of pregnancy? Identify the trimesters of pregnancy. The average duration of pregnancy is 40 weeks (from the first day of the last menstrual period). Pregnancy is divided into three trimesters of about three months each. Each trimester is associated with certain events and conditions that a pregnant woman may expect, such as morning sickness during the first trimester, feeling fetal movements for the first time during the second trimester, and rapid weight gain in both fetus and mother during the third trimester.
Define labour. What event is often a sign that labour will soon begin? Labour is the general term for the entire birth process. Breaking of the amniotic sac and leaking of amniotic fluid often indicates that labour will soon begin.
Identify the stages of labour. There are three stages of labour: dilation of the cervix, birth of the baby, and delivery of the placenta (afterbirth).
Describe the physiological function of female breasts. How is this function controlled? The physiological function of female breasts is lactation, or the production of breastmilk to feed an infant. This is controlled by a positive feedback mechanism. Sucking on the breast by the infant stimulates the release of oxytocin from posterior pituitary gland, which causes the flow of milk. The release of milk stimulates the baby to continue sucking, which in turn keeps the milk flowing.
Identify the functions of the female sex hormones estrogen and progesterone. Estrogen is responsible for prenatal sex differentiation and for sexual maturation and the development of secondary sex characteristics at puberty. It also helps to regulate the menstrual cycle and ovulation after puberty until menopause. Progesterone prepares the uterus for pregnancy each month during the menstrual cycle and helps maintain the pregnancy if fertilization occurs.
Describe the roles of the cervix in fertilization and childbirth. Around the time of ovulation, the cervix makes fertilization more likely by widening the cervical canal (to promote the passage of sperm into the uterus) and the cervical mucus changes to become thinner and more alkaline (making it easier and more hospitable for sperm to survive and travel). During childbirth, the cervical canal dilates greatly to allow the baby to pass from the uterus into the vagina.
18.8 Menstrual Cycle: Review Questions and Answers
What is the menstrual cycle? Why is the menstrual cycle necessary in order for pregnancy to occur? The menstrual cycle refers to natural changes that occur in the female reproductive system each month during the reproductive years except when a woman is pregnant.
What organs are involved in the menstrual cycle? The menstrual cycle involves changes in both the ovaries and uterus. It is controlled by the pituitary hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and also by the ovarian hormones estrogen and progesterone.
Identify the two major events that mark the beginning and end of the reproductive period in females. When do these events typically occur? The female reproductive period is delineated by menarche, or the first menstrual period, which usually occurs around age 12 or 13; and by menopause, or the cessation of menstrual periods, which typically occurs around age 52.
Discuss the average length of the menstrual cycle and menstruation, as well as variations that are considered normal. The menstrual cycle averages 28 days but may vary normally from 21 to 45 days. The average menstrual period is five days long, but may vary normally from two to seven days. These variations in the menstrual cycle occur both between women and within individual women from month to month.
If the LH surge did not occur in a menstrual cycle, what do you think would happen? Explain your answer. Answers may vary. Sample answer: If the LH surge did not occur, I think that ovulation would not occur in this cycle because ovulation is stimulated by the LH surge.
Give one reason why FSH and LH levels drop in the luteal phase of the menstrual cycle. In the luteal phase of the menstrual cycle, the corpus luteum secretes progesterone, which suppresses FSH and LH production.
18.9 Disorders of the Female Reproductive System: Review Questions and Answers
What is cervical cancer? Worldwide, how prevalent is it, and how does it rank as a cause of cancer deaths? Cervical cancer is cancer of the cervix, or neck of the uterus. It occurs when cells of the cervix grow abnormally and develop the ability to invade nearby tissues or spread to other parts of the body. Worldwide, cervical cancer is the second-most common type of cancer in females, and it is the fourth-most common cause of cancer death in females.
Identify symptoms of cervical cancer. What are causes of — and risk factors for — cervical cancer? Early on, cervical cancer often has no symptoms. However, as the disease progresses, it may cause symptoms such as abnormal vaginal bleeding and pain. Most cases of cervical cancer are caused by infection with human papillomavirus (HPV). Risk factors for cervical cancer include smoking and a weakened immune system.
What roles can Pap smears and HPV vaccines play in preventing cervical cancer cases and cervical cancer deaths? A Pap smear can diagnose cervical cancer at an early stage. Where Pap smears are done routinely, cervical cancer death rates have fallen dramatically. The HPV vaccine is expected to greatly reduce the incidence of cervical cancer by preventing HPV infections.
How is cervical cancer treated? Cervical cancer is generally treated with surgery to remove the cancerous cells. This may be followed by radiation therapy and/or chemotherapy.
Define vaginitis and identify its symptoms. Vaginitis is inflammation of the vagina. Symptoms usually include a vaginal discharge, itching, and pain.
What are some of the causes of vaginitis? Which cause is responsible for most of the cases? Vaginitis may be caused by infections with microorganisms or by chemicals in soaps or other products that cause irritation or allergic reactions in the vagina. Infections with microorganisms cause about 90 per cent of cases of vaginitis, with yeast infections being the most common cause.
How is vaginitis diagnosed and treated? Diagnosis of vaginitis may be based on characteristics of the discharge, such as its appearance and pH. The discharge can also be examined microscopically or cultured to determine its exact cause. Treatment of vaginitis depends on the cause and is usually an oral or topical anti-fungal medication (for yeast infections) or antibiotic medication (for bacterial infections).
What is endometriosis, and what are its symptoms? Endometriosis is a disease in which endometrial tissue grows outside the uterus. The tissue commonly grows around the ovaries and Fallopian tubes, and it may bleed during the menstrual period and cause inflammation, pain, and scarring. The main symptom of endometriosis is pelvic pain, which may be severe. Endometriosis may also lead to infertility.
Discuss possible causes of endometriosis. Endometriosis is thought to have multiple causes, including genetic mutations. Retrograde menstruation may be the immediate cause of endometrial tissue escaping the uterus and entering the pelvic cavity. Other possible causes that have been suggested include environmental toxins and autoimmune responses.
How is endometriosis treated? Which treatment is most likely to prevent recurrence of the disorder? Endometriosis is usually treated with surgery to remove the abnormal tissue and medications for pain. A complete hysterectomy in which the internal reproductive organs are removed is most likely to prevent recurrence of endometriosis.
In the case of infection with Trichomonas vaginalis, why is the woman’s sexual partner usually treated at the same time? Answers may vary. Sample answer:Trichomonas vaginalis is usually spread through vaginal intercourse, so if the woman’s sexual partner is not also treated, they can potentially re-introduce the parasite back to the woman or to other sexual partners. Also, if the sexual partner is also infected, they should be treated to protect their own health.
18.10 Infertility: Review Questions and Answers
What is infertility? How is infertility defined scientifically and medically? Infertility is the inability of a sexually mature adult to reproduce by natural means. It is defined scientifically and medically as the failure to achieve a successful pregnancy after at least one year of regular, unprotected sexual intercourse.
What percentage of infertility in couples is due to male infertility? What percentage is due to female infertility? About 30 per cent of infertility in couples is due to male infertility, and about 40 per cent is due to female infertility.
Identify causes of and risk factors for male infertility. Male infertility occurs when there are no or too few healthy, motile sperm. This may be caused by problems with spermatogenesis or by blockage of the male reproductive tract that prevents sperm from being ejaculated. Risk factors for male infertility include heavy alcohol use, smoking, certain medications, and advancing age, to name just a few.
Identify causes of and risk factors for female infertility. Female infertility occurs due to failure to produce viable eggs by the ovaries or structural problems in the Fallopian tubes or uterus. Polycystic ovary syndrome is the most common cause of ovulation failures. Endometriosis and uterine fibroids are possible causes of structural problems in the Fallopian tubes and uterus. Risk factors for female infertility include smoking, stress, poor diet, and older age, among others.
How are causes of infertility in couples diagnosed? Diagnosing the causes of couple infertility generally requires testing both the man and the woman for potential problems. For men, semen is likely to be examined for adequate numbers of healthy, motile sperm. For women, signs of ovulation are monitored, for example, with an ovulation test kit or ultrasound of the ovaries. For both partners, the reproductive tract may be medically imaged to look for blockages or other abnormalities.
How is infertility treated? Treatments for infertility depend on the cause. For example, if a medical problem is interfering with sperm production, medication may resolve the underlying problem so sperm production is restored. Blockages in either the male or the female reproductive tract can often be treated surgically. If there are problems with ovulation, hormonal treatments may stimulate ovulation. Some cases of infertility are treated with assisted reproductive technology (ART). This is a collection of medical procedures in which eggs and sperm are taken from the couple and manipulated in a lab to increase the chances of fertilization occurring and an embryo forming. Other approaches for certain causes of infertility include the use of a surrogate mother, gestational carrier, or sperm donation.
Discuss some of the social and ethical issues associated with infertility or its treatment. Infertility can negatively impact a couple socially and psychologically, and it may be a major cause of marital friction or even divorce. Infertility treatments may raise ethical issues relating to the costs of the procedures and the status of embryos that are created in vitro but not used for pregnancy.
Why is infertility an under-appreciated problem in developing countries? Infertility is an underappreciated problem in developing countries because birth rates are high and children have high economic as well as social value. In these countries, poor health care is likely to lead to more problems with infertility and fewer options for treatment.
Describe two similarities between causes of male and female infertility. Answers may vary. Sample answer: Male and female infertility both may arise from problems in the production of mature gametes (sperm and eggs, respectively) or from blockages in either sex’s reproductive tract.
Explain the difference between males and females in terms of how age affects fertility. While age reduces fertility in both males and females, it is more significant in females. For instance, in females, fertility continuously declines after age 30 and stops completely after menopause. Male fertility gradually declines after age 40, but may never drop to zero.
Do you think that taking medication to stimulate ovulation is likely to improve fertility in cases where infertility is due to endometriosis? Explain your answer. Answers may vary. Sample answer: I think this would be unlikely to help, because in cases where infertility is due to endometriosis, the problem is usually structural — i.e. blockages in the reproductive tract — not a lack of ovulation. The medication may cause more eggs to be ovulated, which could theoretically increase the chance of fertilization slightly, but if the uterus and/or Fallopian tubes were still blocked due to endometriosis, the eggs are unlikely to ever encounter the sperm.
18.11 Contraception: Review Questions and Answers
How is the effectiveness of contraceptive methods typically measured? The effectiveness of contraceptive methods is typically measured as the failure rate. This is the percentage of women who become pregnant using a given method during the first year of use. This can be expressed as the failure rate when the method is used perfectly or as the method is typically used, which is generally much higher.
What is an IUD? An IUD, or intrauterine device, is a small T-shaped plastic structure containing copper or a hormone. It is inserted into the uterus by a physician to prevent pregnancy and can be left in place for months or even years.
Discuss sterilization as a birth control method. Compare sterilization in males and females. Sterilization is the most effective contraceptive method but it requires a surgical procedure and may be irreversible. Male sterilization is usually achieved with a vasectomy, in which the vas deferens are clamped or cut to prevent sperm from being ejaculated in semen. Female sterilization is usually achieved with a tubal ligation, in which the Fallopian tubes are usually tied or cut to prevent sperm from reaching and fertilizing eggs.
What is emergency contraception? When is it used? What are two forms of emergency contraception?Emergency contraception is any form of contraception that is used after unprotected vaginal intercourse. One method is the “morning after” pill, which is a high-dose birth control pill that can be taken up to five days after unprotected sex. Another method is the IUD, which can be inserted up to five days after unprotected sex.
How does the thickness of cervical mucus relate to fertility? How do two methods of contraception take advantage of this relationship? Thinner cervical mucus helps sperm swim through the cervical canal into the uterus. The cervical mucus becomes thinner around the time of ovulation, which increases the chances that the egg will be fertilized. Hormonal birth control pills make the cervical mucus thicker, which makes it harder for sperm to swim through the cervical canal. Also, monitoring cervical mucus thickness and avoiding unprotected intercourse when the cervical mucus becomes thinner is a behavioural method of contraception.
If a newly developed method of contraception had a 35% failure rate, would you consider this to be an effective method? Explain your answer. Answers may vary. Sample answer: No, I would not consider a method of contraception with a 35% failure rate to be a particularly effective method because the least effective methods — behavioural methods such as the fertility awareness method and withdrawal — have a failure rate of around 20–25% at best. The new method would be more effective than nothing (85% pregnancy rate), but nowhere near the effectiveness of other common forms of contraception, such as birth control pills or condoms.
18.12 Case Study Conclusion and Chapter Summary: Review Questions and Answers
Which glands produce the non-sperm fluids that make up semen? What is the rough percentage of each fluid in semen? The prostate gland, seminal vesicles, and bulbourethral glands produce non-sperm fluids that make up semen. Fluid from the seminal vesicles makes up about 70% of semen; fluid from the prostate makes up about 30% of semen; and fluid from the bulbourethral glands makes up a tiny amount of semen.
What is one reason why semen’s alkalinity assists in reproduction? Answers may vary. Sample answer: Semen is alkaline in part because it helps protect the sperm when they encounter acidic secretions inside the female vagina. This gives them a greater chance of being able to survive to fertilize an egg.
What are three things that pass through the cervical canal of females, going in either direction? Answers may vary. Sample answer: Semen (or sperm); shed endometrial lining (menstrual period); a baby during childbirth.
Other than where the cancer originates, what is one difference between prostate and testicular cancer? Answers may vary. Sample answer: Testicular cancer often affects younger men, while prostate cancer usually affects older men.
If a woman is checking her basal body temperature each morning as form of contraception, and today is day 12 of her menstrual cycle and her basal body temperature is still low, is it safe for her to have unprotected sexual intercourse today? Why or why not? Answers may vary. Sample answer. No, it is not safe for her to have unprotected intercourse today if she does not want to get pregnant. This is because basal body temperature rises only after ovulation has already occurred. On day 12, she is likely close to ovulating — if she hasn’t already — because day 14 is the average day of ovulation for a 28 day cycle and the timing can vary. Also, sperm can live for up to a week in the female reproductive tract, so if they have unprotected sex today and she ovulates within the next few days, she can become pregnant.
Where is a diaphragm placed? How does it work to prevent pregnancy? A diaphragm is placed over the woman’s cervix before sexual intercourse. This blocks sperm in the vagina from entering the cervical canal. If the sperm are blocked here, they cannot enter the uterus and Fallopian tubes to fertilize the egg.
Why are the testes located outside of the body? The testes are located outside of the body because the optimal temperature for spermatogenesis is about 2 degrees Celsius (almost 4 degrees Fahrenheit) lower than core body temperature.
Why is it important to properly diagnose the causative agent when a woman has vaginitis?Answers may vary. Sample answer: Although vaginitis is most commonly caused by yeast, it can also be caused by bacteria or other types of microorganisms. Vaginitis also may or may not be transmitted sexually. Therefore, it is important to know the specific causative agent so it can be treated effectively, because different microorganisms need to be treated with different medications (for instance, anti-fungal vs. antibiotics) and the woman’s sexual partner may need to be treated if it is sexually transmitted.
Describe two ways in which sperm can move through the male and/or female reproductive tracts. Answers may vary. Sample answer: Sperm can move by using their tails to swim. Another way they can move is through peristalsis of the muscles in parts of the male reproductive tract (such as the vas deferens) that force sperm through the tract and out of the penis during an ejaculation.