ANIMAL REPRODUCTIVE SYSTEMS

41 ____________________________________________________________________________________________ ANIMAL REproductive systems Chapter Outline Intersex conditions Modes of animal Reproduction Asexual Reproduction Sexual Reproduction Gamete Formation and Fertilization Nourishing Developing Young Reproductive System of Human MAles The Male Gonads Reproductive Ducts and Accessory Glands Disorders of the Male Reproductive Tract sperm formation Germs Cells to Mature Sperm Hormonal Control of Sperm Formation reproductive system of human females Female Gonads Reproductive Ducts and Accessory Glands The Menstrual Cycle Disorders of the Female Reproductive Tract Preparations for pregnancy The Ovarian Cycle The Uterine Cycle PMS TO HOT FLASHES when gametes meet Sexual Intercourse Fertilization preventing or seeking pregnancy Birth Control Options Infertility Sexually Transmitted Diseases Consequences of Infection Major Agents of Sexually Transmitted Diseases INTERSEX CONDITIONS (REVISITED) SUMMARY data analysis exercise Self-Quiz critical thinking Objectives 1. Understand how asexual reproduction differs from sexual reproduction. Know the advantages and problems associated with having separate sexes. 2. Describe the structure and function of the human male and female reproductive systems. 3. Understand conditions that may impact the male and female reproductive tracts. 4. Know the principal means of controlling human fertility. 5. Know the various STDs presented in this chapter and the various modes of transmission. Key Terms asexual reproduction sexual reproduction intersex condition hermaphrodite external fertilization internal fertilization placenta gonads testes, testis testosterone scrotum seminiferous tubules sperm secondary sexual traits puberty epididymis vas deferens ejaculatory ducts urethra penis semen seminal vesicles prostate gland prostaglandins bulbourethral glands prostate cancer testicular cancer spermatogonia primary spermatocytes Sertoli cells secondary spermatocytes spermatids testosterone luteinizing hormone, LH follicle-stimulating hormone, FSH gonadotropin releasing hormone, GnRH Leydig cells ovaries oocyte oviduct uterus endometrium cervix vagina labia majora labia minora clitoris estrous cycle menstrual cycle follicular phase ovulation luteal phase corpus luteum estrogens progesterone menopause primary oocytes ovarian follicle zona pellucida secondary oocyte polar body erection ejaculation orgasm ovum abstinence rhythm method withdrawal douching vasectomy tubal ligation spermicidal foam spermicidal jelly diaphragm condoms birth control pill birth control patch morning after pills abortion in vitro fertilization sexually transmitted diseases, STDs human papillo-mavirus, HPV genital warts trichomoniasis chlamydial infection genital herpes gonorrhea syphilis HIV AIDS Lecture Outline 41.1 Intersex Conditions A. The International Olympic Committee (IOC) began gender testing in 1968. 1. A test that detects the SRY gene on the Y chromosome is used to determine sex. 2. The SRY gene triggers testes development in a normal XY individual. 3. The testing program has not unveiled men pretending to be women, but it has turned up people brought up and believing to be women but carrying a Y chromosome. B. Individuals with androgen insensitivity syndrome (AIS) have female reproductive organs, but also testes within the body cavity. 1. These AIS individuals are usually raised as females, but should have the testes removed to reduce cancer risks. 2. Some babies are born with partial AIS, which gives them abnormal genitalia for either sex and often requires corrective surgery. C. Intersex conditions challenge our thinking about what is a female and what is a male. 41.2 Modes of Animal Reproduction A. Asexual Reproduction 1. Asexual reproduction is a useful strategy in stable environments. 2. Asexual reproduction by fragmentation, budding (for example, sponge), or parthenogenesis results in offspring identical to the parents. a. In fragmentation, a portion of the parent becomes the offspring. b. Budding is the condition in which a small offspring grows off of the parent and then separates. c. In parthenogenesis an unfertilized egg becomes the offspring. B. Sexual Reproduction 1. In sexual reproduction, the male and female gametes combine at fertilization. 2. Sexual reproduction permits adaptation through variation but is biologically costly because the sexes are separate. a. Animals must produce gametes and must find each other (usually) for fertilization to occur. 3. Through sexual reproduction, the offspring are more likely to have a gene combination that is suitable to their new environment. C. Gamete Formation and Fertilization 1. Some animals, such as tapeworms and roundworms, are hermaphrodites, producing both eggs and sperm at the same time. 2. More typically, vertebrates have separate sexes that are fixed for life—they are either male or female. 3. Most land animals have internal fertilization, while most marine animals use external fertilization. 4. Offspring may develop inside the mother or outside of the maternal body. D. Nourishing Developing Young 1. Most animals are nourished by yolk inside of the amniote egg. 2. Placental mammals utilize the placenta as a means for the developing offspring to obtain nutrients. 41.3 Reproductive System of Human Males A. The Male Gonads 1. Human males have two testes located in the scrotum. a. This is the site of sperm development, and the testes must be several degrees cooler than body temperature. b. Testosterone, a sex hormone, is also produced in the testes. c. The male reproductive system includes accessory organs, glands, and ducts. 2. Sperm production begins during puberty, the stage when secondary sexual characteristics emerge. B. Reproductive Ducts and Accessory Glands 1. Each testis contains many seminiferous tubules where sperm are continuously formed. 2. Sperm move from a testis epididymis (for maturation and storage) vas deferens ejaculatory ducts urethra (located inside the penis). 3. The sperm-bearing fluid (semen) is formed by secretions from the seminal vesicles (fructose and prostaglandins) and the prostate (buffers against acidic vagina). 4. The bulbourethral glands secrete a mucus-rich fluid into the vagina during sexual arousal. C. Disorders of the Male Reproductive Tract 1. The prostate gland can enlarge due to cancer or inflammation. a. Prostate cancer is the second most common type of cancer causing death in males. 2. There are about 7,000 cases of testicular cancer each year in the United States. 3. Routine examination and blood tests are necessary to detect these subtle cancers. 41.4 Sperm Formation A. Germ Cells to Mature Sperm 1. Sperm form in the walls of the seminiferous tubules of the testes. 2. Diploid spermatogonia undergo mitosis primary spermatocytes, which undergo meiosis I haploid secondary spermatocytes, which undergo meiosis II haploid spermatids mature sperm. 3. Sertoli cells in the tubule provide nourishment and chemical signals to the developing sperm. 4. Each sperm has a head (nucleus and cap), midpiece (mitochondria), and tail (flagellum). B. Hormonal Control of Sperm Formation 1. Testosterone, produced by Leydig cells located between the lobes in the testes, stimulates spermatogenesis. a. Testosterone also initiates the secondary sexual characteristics and helps to develop normal sexual behavior. 2. Luteinizing hormone (LH) is released from the anterior pituitary (under prodding by GnRH from the hypothalamus) and stimulates testosterone production. 3. GnRH also causes the pituitary to release FSH, which stimulates the production of sperm, beginning at puberty. 41.5 Reproductive System of Human Females A. Female Gonads 1. The ovaries are responsible for maturation of oocytes. a. Ovaries also produce the hormones estrogen and progesterone. B. Reproductive Ducts and Accessory Glands 1. The egg is released from the ovary oviduct uterus (zygote will implant in its lining, the endometrium). 2. The lower part of the uterus is the cervix, which extends into the vagina, which in turn leads to the outer genitalia: labia majora, labia minora, and clitoris. C. The Menstrual Cycle 1. Humans and other primates have a menstrual cycle. 2. During each cycle an oocyte matures and escapes from the ovary. a. If it is fertilized, the egg may implant in the endometrium. b. If there is no implantation, the uterine lining is sloughed at the end of each cycle of (approximately) 28 days. 3. A decline in hormone secretions correlates with the onset of menopause, the cessation of a female’s reproductive capacity. D. Disorders of the Female Reproductive Tract 1. Many women have fibroid tumors that cause additional bleeding and pain. 2. Uterine cancer may cause additional bleeding between periods and can be diagnosed by Pap smears. 3. Ovarian cancer is more difficult to detect, so it is more deadly than uterine cancer. 41.6 Preparations for Pregnancy A. The Ovarian Cycle 1. At birth about two million immature eggs (primary oocytes) are already present and arrested in meiosis I. 2. Of the approximately 300,000 oocytes still present at age seven, only about 400–500 will mature in a lifetime. 3. The follicle consists of a layer of cells (granulosa) surrounding the primary oocyte; the granulosa cells gradually deposit a layer of material around the follicle. 4. During the menstrual cycle, one oocyte resumes meiosis I to form a secondary oocyte and a polar body (both haploid). 5. At about mid-cycle, there is a surge of LH that causes ovulation—the release of the secondary oocyte. 6. Following ovulation, the remaining follicle becomes a corpus luteum, which secretes estrogen and progesterone. a. If there is no fertilization of an egg, the corpus luteum disintegrates. b. If a pregnancy occurs, the corpus luteum remains functional until the placenta is fully formed. B. The Uterine Cycle 1. During the first five days of the menstrual cycle, the innermost lining of the uterus sloughs off. 2. During the next phase, the uterine lining is rebuilt. 3. During the first half of the cycle, the hypothalamus signals the anterior pituitary to release LH and FSH, which in turn stimulate the ovary to secrete estrogen. 4. The corpus luteum persists for about 12 days, secreting progesterone that inhibits further FSH and LH secretion. 5. If fertilization does not occur, the corpus luteum degenerates, progesterone and estrogen levels fall, and FSH and LH are again secreted to begin another cycle. 41.7 PMS to Hot Flashes A. PMS, premenstrual syndrome, is related to discomfort a week or two before menstruation. 1. Hormones cause milk ducts to enlarge, making the breasts swell and become tender. 2. Cycle-induced changes also cause depression, irritability, anxiety, headaches, and sleeping disorders. B. Menstrual pain can be caused by prostaglandins secreted during menstruation that stimulate contractions of smooth muscle in the uterine wall. 1. Many women do not even notice these contractions. 2. Others may experience a dull ache or sharp pain. C. Menopause occurs when the eggs are no longer maturing and the hormone levels drop. 1. Three-fourths of women in menopause get hot flashes and night sweats. 2. Hormone replacement, diet, alcohol, and exercise can lessen hot flashes and night sweats. 41.8 When Gametes Meet A. Sexual Intercourse 1. In male sexual arousal, the spongy tissue spaces inside the penis become filled with blood to cause an erection. 2. During coitus, mechanical stimulation of the penis causes involuntary contractions that force semen out and into the vagina. 3. Ejaculation in the male and similar contractions in the female are termed orgasm. 4. Viagra® medication is prescribed to counter erectile dysfunction in men. B. Fertilization 1. Of the 150 million to 350 million sperm deposited in the vagina during intercourse, only a few hundred ever reach the upper region of the oviduct where fertilization occurs. a. Sperm may live for about three days following ejaculation. b. About 30 minutes after being deposited in the vagina the sperm may reach the oviducts, the entry to the fallopian tubes. 2. Only one sperm will successfully enter the cytoplasm of the secondary oocyte after digesting its way through the zona pellucida. a. The arrival of that sperm stimulates the completion of meiosis II, which yields a mature ovum. b. The sperm nucleus fuses with the egg nucleus to restore the diploid chromosome number. 41.9 Preventing or Seeking Pregnancy A. Birth Control Options 1. Abstinence is most effective, but may be unrealistic. 2. In the rhythm method, there is no intercourse during the days when an egg is capable of being fertilized. 3. Withdrawal before ejaculation would seem to be effective, but is not. 4. Douching is similarly ineffective due to the speed with which sperm enter the uterus. 5. Surgery to cut and tie the oviducts (tubal ligation) or vas deferens (vasectomy) is effective and generally considered an irreversible method to prevent sperm and egg union. 6. Spermicidal foam and jelly are toxic to sperm but not reliable unless used in combination with a barrier device like a diaphragm. 7. A diaphragm fits over the cervix and prevents entry of sperm into the uterus. 8. Condoms prevent sperm deposition in the vagina but must be used with care. 9. The birth control pill (and birth control patch) contains synthetic female hormones and prevents ovulation when taken faithfully according to directions; the patch delivers the same hormones as the pill but is applied to the skin. 10. Progestin injections (Depo-Provera®) or implants (Norplant®) inhibit ovulation over several months. 11. “Morning-after pills” intercept pregnancy by blocking fertilization or preventing implantation. B. Infertility 1. About two-thirds of the causes for infertility are due to a problem with the female. a. A problem with hormone levels may prevent ovulation. b. Polycystic ovarian syndrome allows the follicles to mature, but ovulation does not occur. c. Endometriosis or scarring from STDs can cause discomfort and may result in a tubal pregnancy. i. A tubal pregnancy cannot survive, because there is not enough space or nutrition for the developing fetus. 2. Some reasons for infertility relate to the male reproductive system. a. Some males have either a low sperm count or a high number of abnormal sperm. b. Problems with scarring or ejaculation can also impact fertility. 41.10 Sexually Transmitted Diseases A. Consequences of Infection 1. Sexually transmitted diseases (STDs) infect millions of Americans each year. a. The social consequences are enormous; women develop more complications than men. b. Pelvic inflammatory disease may cause pain and lead to infertility. c. STDs can harm the unborn child. B. Major Agents of Sexually Transmitted Disease 1. Trichomonas vaginalis, a protozoan, causes soreness and discharge from the vagina; males are usually symptom-free. a. Untreated infections can lead to infertility. 2. Chlamydia trachomatis causes the most common STD, chlamydia. a. It shows few symptoms but can lead to pelvic inflammatory disease. b. Chlamydia may cause pneumonia and eye infections in the offspring of an infected mom. 3. Neisseria gonorrhoeae, a bacterium, enters the body through mucous membranes during sexual intercourse and causes gonorrhea. a. Because the initial symptoms are mild, treatment is often delayed, allowing the bacterium to multiply out of control. 4. The spirochete Treponema pallidum enters the body from an infected sexual partner and causes syphilis. a. Initially the spirochetes produce a localized ulcer that heals, but the organisms continue to multiply in the spinal cord, brain, eyes, bones, joints, and mucous membranes with serious consequences. 5. Human papillomavirus (HPV) is becoming widespread in the United States. a. Some strains cause genital warts; others can cause cervical cancer. b. There is now a vaccine to protect against HPV infection in both males and females. 6. The STD herpes is caused by the Herpes simplex virus, which can invade the mucous membranes of the mouth or genitals by direct contact. b. Blisters may form, disappear, and then reappear under stressful conditions. c. If a mom has an active infection at the time of delivery, it can have drastic effects on the infant. 7. Infection by the human immunodeficiency virus (HIV) leads to AIDS, an incurable STD that leads to a complete breakdown of the immune system. a. Opportunistic infections are the eventual cause of death. b. HIV spreads by anal, vaginal, and oral intercourse as well as by intravenous drug use. c. The use of a condom and lubricant can prevent the spread of HIV. 41.11 Intersex Conditions (Revisited) In the past, XY individuals born with a micropenis had surgery to make them a female. Studies have shown that the majority of these individuals were unhappy with their sexual reassignment. Suggestions for Presenting the Material • Most students approach the topic of reproduction with a sigh of relief and an attitude that says “finally, something I know everything about.” The intuitive instructor will build upon what accurate information the students already know and will gently, but authoritatively, correct misinformation. This also prohibits any belittling of incomplete, or inaccurate, “folklore.” Tell them that they will definitely learn some facts that they did not previously know about reproduction. • The sequence of topics is logically presented in the chapter: male and female structures, menstrual cycle, sexual union, fertility control, and prenatal development. • There are numerous excellent animated figures available to help you present this material. The animated figures provide excellent visual context for your students. • When comparing the male and female systems, it is helpful to note that the male produces and delivers sperm, much as the female produces and delivers eggs. However, the female also provides: (a) a site for fertilization, and (b) a site for embryonic and fetal development. This provides a convenient lead into the discussion of the menstrual cycle. • The details of the menstrual cycle are of interest to both sexes but especially to females, of course. Because events are happening simultaneously in the pituitary, ovary, and uterus, it is virtually a necessity to keep Figure 41.10 and 41.11 in constant view. The critical feature of this figure is the timeline along the bottom, which puts all events into perspective. • These points need emphasis in your lecture on female reproduction: a. Females are born with a finite number of eggs, which means eggs grow old (implications for causing genetic defects in offspring). b. Menstrual cycle can be defined as “the monthly release of an egg and all the preparations for it.” c. Retention or sloughing of endometrium is determined by progesterone levels at the end of the menstrual cycle. • You may be able to surprise your students with the fact that only a few days of each month comprise the “fertile period.” But hasten to inform them that the fertile days can “move around” depending on a variety of nutritional, psychological, and health factors. • The most practical aspect of the chapter is Section 41.9 “Preventing or Seeking Pregnancy.” Students are eager for this information, especially when it can be presented with special reference to the mode of action of each device. Be sure to emphasize the effectiveness of each method as shown in Table 41.2. • The topic of sexual diseases is presented in this chapter in Section 41.10. Individual instructors may, or may not, wish to present this. But certainly some reference, even without details, should be made to the toll these diseases exact on society. Older students in your class may be less informed than some of the younger ones about reproduction due to the revamping of sex education in school. Undoubtedly your older female students had a quick movie on their menstrual cycle while the boys were in gym class. Today’s youth see movies about the sexual development of both sexes. This way they are much more informed about the entire subject of reproduction. Do your students agree with this newer method of sexual education? What are the advantages and disadvantages of asexual and sexual reproduction? Why is it advantageous for an animal like a snail to be a hermaphrodite? (This way, when it finally catches up with another snail—mating can always occur!) When discussing male and female reproduction, it is useful to mention their similarities. First of all, some of the same hormones play an integral role in both systems. Be sure to point out the following pairs of homologous structures: Penis – clitoris Scrotum – labia majora Testes – ovaries Can you find other homologous structures in the male and female systems? Another amazing thing is the sheer numbers involved with reproduction. A female has several million eggs and the average ejaculation contains somewhere between 50–500 million sperm! Classroom and Laboratory Enrichment • Because you probably teach students with a great range of sexual knowledge and experience, adjust your enrichment activities accordingly. For example, many students will appreciate observing birth control devices or slide photos of them. • If you decide to present details of the physical manifestations of sexually transmitted diseases, use discretion in which slides you show and give warning before showing them so students may choose to look away. • Students enjoy bragging about their sexual knowledge. Perhaps you can bring some perspective to this by preparing a true/false quiz of common facts and fallacies associated with human reproduction. Allowing the students to remain anonymous, administer the quiz prior to your lecture. Tabulate the results and report them to the class as you give the accurate information. Show purchased slides of the various stages of oocyte development. In addition, show a prepared slide of sperm. Can the students identify the three main portions: the head, the midpiece, and the tail? To ensure that your students understand the huge difference in size between an egg and a sperm, be sure to show a photo of sperm surrounding an egg. An excellent micrograph can be found at the following web address: _http://news.bbc.co.uk/nol/shared/spl/hi/pop_ups/03/health_ivf_step_by_step/img/1.jpg_ Create a Jeopardy-style quiz by using the format at the following website: _http://jeopardylabs.com/_ It is important to stress to the class that both sexes have FSH and LH, but they were named for their female functions. Note that in the different phases of the menstrual cycle, events take place both in the ovaries and the uterus. Classroom Discussion Ideas • These issues and decisions are emotional, and professionals can help make sound decisions. How much should professional input play a role in these decisions? • List pros and cons of delaying the surgery and also performing the surgery as soon as possible. At what age to you think a child is qualified to determine his/her sexual orientation? What are the most important criteria, genetic testing or the determination by a surgeon of which procedure would be a safer alternative? What methods or combinations of methods do you think sports officials should use to determine the sex of athletes? Additional Ideas for Classroom Discussion • All animals reproduce at rates sufficient to maintain their population. Humans are the only ones whose proliferation seems to be under very few limiting factors. Is this so? Why? • Using anatomical terms, explain why men who have had a vasectomy operation are still able to expel normal amounts of semen but no sperm. • Explain the events that result in the production of identical and fraternal twins. • What propels sperm from their point of origin to the opening where they exit the body? • What mechanisms prevent the entry of more than a single sperm into the egg? • Many communities, and even states, restrict the teaching of human reproduction. Why do you think this body system is singled-out over, say, digestion or respiration for such a prohibition? Non-disjunction occurs more often in older eggs. What diseases increase their incidences with advanced maternal age? Are there tests to detect these abnormalities? At what age do physicians recommend amniocentesis? When mentioning birth control methods, it should be addressed that a vasectomy is a less-invasive procedure than a tubal ligation. With a tubal ligation, it is necessary to enter the abdominopelvic body cavity, whereas, a vasectomy can be performed by making an incision in the scrotum. How Would You Vote? Classroom Discussion Ideas • Monitor the voting for the online questions. This issue is a tough one. These decisions are very personal. Families need to consider input from the medical professional community before making the decision to perform surgery or not. It is almost impossible to measure the effects of having the surgery or delaying it. Research the issue more using CengageNow. Undoubtedly the surgeon will suggest reassignment based on which procedure is less invasive. Should this be the sole criteria? If genetic testing is performed, should the reassignment be based on those results? How would you raise the child until they are old enough to decide? Do you tell others that your child is a boy or a girl? Would having no sexual identity until the gender assignment is made be just as deleterious as assigning the inappropriate sex? • Have students complete class polling using the JoinIn clickers. Term Paper Topics, Library Activities, and Special Projects • It is a curious, but real, fact that most sex crimes are committed by males. Investigate what psychologists and physicians say about the underlying cause(s) for this behavior. • Sexual dysfunction is a frustrating situation for those involved, whether male or female. Prepare a list, based on your reading, of the most prevalent disorders and their treatment. • We hear about “sperm banks” now and then. Do such repositories actually exist? Where are they? How do they function? • Any interruption in the menstrual cycle, whether temporary or permanent, is cause for concern. Report on the causes and effects of the cessation of menstruation in females who drastically reduce their body weight (anorexia) or body fat (as in body building). • Search for the physiological explanation for the cessation of menstruation (menopause)—usually when a woman is between the ages of 40 and 50. Is there any comparable phenomenon in men? • It is known that overcrowding and stressful conditions reduce reproductive behavior in rodents. Is there any published evidence of such a phenomenon in humans? • Research the family planning practices of China. Find out the current practice of child restriction and the effects this is having on China’s demography. There have been articles written about the rewards given to families who have daughters; is this a valid or regular practice in the country? Examine the eggs (or photographs) of different species. Which have more yolk? Which have only small amounts of yolk? What is the function of the yolk sac in humans? Research the details of “female circumcisions.” In what countries is this procedure performed? Why is this performed? Is there any medical benefit from this procedure? Make a chart that compares spermatogenesis (sperm formation) with oogenesis (egg formation). Research the development of the Gardasil injection to prevent HPV infection. When were birth control pills invented? How do they “fool” the body so that you avoid a pregnancy? What are the health risks from taking the pill? How does an ovulation test kit work? What hormone does it measure? Choose an STD to report on. Make sure to include the symptoms and potential treatments in your document. Possible Responses to Critical Thinking Questions 1. Hypertension (high blood pressure) causes the blood vessels to constrict; drugs work to keep the blood flowing through the vessels. High blood pressure drugs interfere with sexual behavior by opening the blood outflow from the penis during stimulation. The drugs block the vascular receptors on the smooth muscle as blood fills a penis that would normally stay erect. Instead of keeping the blood in until ejaculation, as normal, channels are opened as the blood flows in and the penis cannot stay erect. This leads to erectile dysfunction, loss of sex drive, and ejaculatory failure. 2. An analysis of shared derived characteristics would help to answer these questions. Essentially, you need to gather information to establish relationships to the common ancestor Did the common reptilian ancestor fly or not? More information regarding bone structure would help to answer this question. The ancestors tracing further back most likely would not have a penis, but those diverging later on the evolutionary timeline might have a penis. 3. Follicle stimulating hormone (FSH), as the name implies, stimulates follicles to mature. If a woman had additional FSH, she may have more than one follicle that reaches maturity and is released during ovulation. If two eggs become fertilized at the same time, fraternal twins will result. 4. Lysosomes are organelles in animal cells that contain enzymes that degrade and recycle organelles. The lysosome digests the sperm mitochondria. Possible Responses to Data Analysis Exercise Questions Some females are born with genitals that appear to have varying degrees of masculinity. Scientists have discovered that females that have a 21-hydroxylase deficiency also have higher testosterone levels. This study was performed to see if administration of dexamethasone would prevent formation of these intersex variations. In this study, four daughters that were born from moms given dexamethasone had normal female genitals. According to the data provided, none of the untreated women had earlier phenotypically normal daughters. All of the women that previously had daughters with level 4 or 5 masculinization had daughters that showed improvement. In this experiment, it shows that administration of dexamethasone to pregnant women can reduce the effects of her developing daughter’s 21-hydroxylase deficiency. 414 Chapter Forty-One Animal Reproductive Systems 413 414 Chapter Forty-One Animal Reproductive Systems 413 414 Chapter Forty-One Animal Reproductive Systems 413 414 Chapter Forty-One Animal Reproductive Systems 413 414 Chapter Forty-One Animal Reproductive Systems 413