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Name Class Date 34.3 The Reproductive System Lesson Objectives Describe the effects the sex hormones have on development. Name and discuss the structures of the male reproductive system. Name and discuss the structures of the female reproductive system. Describe some of the most common sexually transmitted diseases. Lesson Summary Sexual Development Hormones released by the ovaries and testes cause sexual development during puberty, a period of rapid growth and sexual maturation that usually starts between the ages of 9 and 15. At the end of puberty, the male and female reproductive organs are fully developed and become fully functional. The Male Reproductive System The main role of the male reproductive system is to make and deliver sperm. ▶ The testes are the main organs of the male system. Two testes are held in an external sac called the scrotum. The testes make sperm in tiny tubes called seminiferous tubules. The sperm mature and are stored in an epididymis. A tube called a vas deferens carries sperm from each testis to the urethra within the penis. ▶ Along the way, secretions of several glands form a nutrient-rich fluid called seminal fluid. The combination of sperm and seminal fluids is called semen. Semen leaves the body through the urethra. Contractions eject semen from the penis in a process called ejaculation. ▶ A mature sperm cell consists of a head that contains the nucleus, a midpiece that is packed with mitochondria, and a flagellum that propels the sperm. The Female Reproductive System The main roles of the female reproductive system are to make eggs and prepare the female body to nourish an embryo. ▶ The ovary is the main organ of the female system. Each ovary has thousands of follicles, which are clusters of cells that surround an egg. A mature egg moves through the Fallopian tube to the uterus, which is connected to the outside of the body by the vagina. ▶ Beginning in puberty, the female body goes through a menstrual cycle, a series of events that prepares the body to care for a fertilized egg. The menstrual cycle has four phases: • Follicular phase: An egg matures in its follicle. • Ovulation: The mature egg is released from the ovary. • Luteal phase: The follicle develops into a structure called the corpus luteum. • Menstruation: The lining of the uterus falls away and leaves the body through the vagina if the egg is not fertilized. Sexually Transmitted Diseases A disease spread during sexual contact is called a sexually transmitted disease (STD). Bacteria and viruses can cause STDs. Chlamydia, syphilis, gonorrhea, and AIDS are STDs. Lesson 34.3 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 536 Name Class Date Sexual Development For Questions 1–3, write the letter of the correct answer on the line at the left. B 1. Male and female embryos are nearly identical until the A. second week of development. C. third month of development. B. seventh week of development. D. fifth month of development. A 2. Which hormone, when produced in an embryo, triggers a male pattern of development? A. testosterone C. estrogen B. progesterone D. adrenalin D 3. The period of human development that includes rapid growth and sexual maturation is called A. adolescence. C. maturity. B. childhood. D. puberty. The Male Reproductive System For Questions 4–8, match each structure of the male reproductive system with its description. Description Structure C 4. epididymis A. External sac that holds male gonads A 5. scrotum B. The primary male reproductive organ D 6. seminiferous tubule C. Structure in which sperm mature B 7. testis D. Structure in which meiosis occurs E 8. vas deferens E. The tube through which sperm travel to the urethra For Questions 9–12, complete each statement by writing the correct word or words. prostate 9. The seminal vesicles, gland, and bulbourethral gland produce a seminal nutrient-rich fluid called fluid. 10. Sperm mixed with the seminal fluid is called 11. Signals from the autonomic semen . nervous system cause sperm to be ejaculated. midpiece of a sperm cell contain mitochondria that supply energy to the flagellum , which propels the sperm forward. 12. The The Female Reproductive System For Questions 13–16, complete each statement by writing the correct word or words. 13. The primary reproductive organs of females are the 14. The function of a(n) 15. Only about mature ovum. 400 follicle ovaries . is to help an egg mature. of the 400,000 eggs a female is born with develop into a 16. The structure of the female reproductive system in which the embryo develops is called uterus the . Lesson 34.3 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 537 Name Class Date For Questions 17–20, match each phase of the menstrual cycle with the correct event. Phase Event C 17. Follicular phase A. An unfertilized egg leaves the body. D 18. Ovulation B. The egg travels through a Fallopian tube. B 19. Luteal phase C. An egg within a follicle develops. A 20. Menstruation D. An egg is released from an ovary. 21. Complete the concept map to explain what the outcomes of a menstrual cycle can be. Mature ovum enters the Fallopian tube No sperm are in female tract Sperm are present in female tract Menstruation will occur Fertilization could result Sexually Transmitted Diseases For Questions 22–24, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. Chlamydia 22. AIDS is the most common bacterial STD. True 23. Chlamydia damages the reproductive tract and can cause infertility. True 24. Hepatitis B and genital herpes are viral STDs. 25. How is the menstrual cycle an example of the body’s use of negative feedback? SAMPLE ANSWER: The female body uses negative feedback during the menstrual cycle to maintain its readiness for reproduction. The presence of higher levels of hormones such as estrogens and progesterone causes their production to slow. In turn, the dropping levels of the hormones stimulate their increased production. Lesson 34.3 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 538 Name Class Date 34.4 Fertilization and Development Lesson Objectives Describe fertilization and the early stages of development. Identify the major events of later stages of development. Lesson Summary Fertilization and Early Development Fertilization is the joining of a sperm and an egg. Following fertilization, a series of events called development begins. ▶ A fertilized egg is called a zygote. The zygote divides and undergoes repeated rounds of mitosis and develops into a hollow ball of cells called a blastocyst. ▶ About a week after fertilization, the blastocyst attaches to the wall of the uterus in the process of implantation. At the same time, cells of the blastocyst start to specialize through differentiation. Some cells migrate to form two cell layers—the ectoderm and the endoderm. ▶ A third layer of cells is produced by a process called gastrulation, in which cells from the ectoderm migrate to form the mesoderm. The three layers eventually develop into the different organs of the embryo. ▶ During neurulation, the notochord and the neural tube form. The neural tube eventually develops into the brain and spinal cord. ▶ As the embryo develops, membranes for protection and nourishment also form. Part of one membrane combines with the uterine lining to form the placenta. Mother and embryo/fetus exchange gases, food, and waste products across the placenta. The umbilical cord connects the embryo/fetus to the placenta. ▶ After eight weeks of development, the embryo is called a fetus. By the end of three months, most organs are fully formed. Later Development Another six months of development occurs before birth. ▶ During months 4–6, the fetus’s tissues become specialized and organs such as the heart begin to function. ▶ During months 7–9, the fetus’s organ systems mature as the fetus grows in size and mass. The lungs and the central nervous system complete their development. ▶ Childbirth occurs about nine months after fertilization, when hormones cause contractions in the mother’s uterus. The contractions first push the baby out through the vagina. Then, more contractions expel the placenta and amniotic sac from the uterus. Shortly after birth, the mother’s breast tissue begins to produce milk that contains everything the baby needs for the first months of life. ▶ The placenta is a barrier to many harmful agents, but some are able to pass through it, such as viruses that cause AIDS and German measles. Alcohol, drugs, and smoking also have negative effects on embryos and fetuses. Prenatal care and advancements in medical technology have lowered the infant mortality rate. Lesson 34.4 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 539 Name Class Date Fertilization and Early Development For Questions 1–4, complete each statement by writing the correct word or words. fertilization 1. The fusion of a sperm with an egg is called 2. During implantation, the blastocyst . embeds itself into the lining of the uterus. 3. Embryonic structures called chorionic villi combine with the uterine lining to form placenta the . 4. The embryo is surrounded by fluid called the amniotic fluid. 5. Complete the table by identifying events and structures of early development. Event or Structure What It Is Fertilization The process in which sperm joins an egg Ectoderm The layer of cells that develops into the skin and nervous system Gastrulation Process that results in the formation of three cell layers Neurulation Early stage in the development of the nervous system Endoderm The innermost layer of cells in the early embryo that forms the lining of some organs Amniotic sac Fluid-filled structure that cushions and protects the embryo Placenta Embryo’s organ of respiration, nourishment, and excretion Mesoderm Forms internal structures such as bones and muscles Umbilical cord Structure that connects the fetus to the placenta Later Development 6. What major changes occur in a developing fetus during months 4–6 of pregnancy? The tissues of the fetus become more complex and specialized, and they begin to function. The heart becomes larger. Bone replaces cartilage. 7. What major changes occur in a developing fetus during months 7–9 of pregnancy? The organ systems of the fetus mature, and the organs undergo changes that prepare them for life outside of the uterus. The fetus doubles in size. It begins to regulate its own body temperature. The nervous system and lungs complete development. Lesson 34.4 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 540 Name Class Date For Questions 8–13, write the letter of the correct answer on the line at the left. B 8. The contractions of labor before childbirth are triggered by A. the amniotic fluid. B. the hormone oxytocin. C. the umbilical cord. D. the uterine wall. C 9. The term “afterbirth” refers to the A. amnion and the chorion. B. clamping of the umbilical cord. C. placenta and amniotic sac. D. production of milk for the baby. B 10. What is a belly button? A. a structure with an unknown purpose B. a scar left from the umbilical cord C. remains of the notochord D. the point where implantation occurred D 11. Which hormone causes the mother’s breast tissue to begin producing milk? A. estrogen B. oxytocin C. progesterone D. prolactin D 12. Using alcohol during pregnancy can harm a developing embryo, especially its A. reproductive system. B. circulatory system. C. endocrine system. D. nervous system. A 13. Which public health measure has decreased the incidence of spina bifida? A. the addition of folic acid to grain products B. the development of new types of baby formula C. the programs aimed at reducing smoking and alcohol use D. the use of a vaccine that prevents German measles 14. Women with Type 1 diabetes may face challenges controlling blood sugar levels during pregnacy. Early in pregnancy, the developing fetus removes glucose from the mother’s blood at a great rate. Would this raise or lower her need for insulin? This would lower her need for insulin. By removing a lot of glucose from her blood, the fetus would help keep her blood glucose levels at an appropriate level. Lesson 34.4 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 541 Name Class Date Chapter Vocabulary Review On the lines provided, label the structures of the male reproductive system that correspond to the numbers in the diagram. 1. 1. Vas deferens 2. Epididymis 3. Testis 2. 3. For Questions 4–10, match the term with its definition. Term Definition F 4. endocrine gland A. Mixture of sperm and seminal fluids G 5. exocrine gland B. Attachment of the blastocyst to the uterine wall E 6. gastrulation D 7. hormone C. Discharge of uterine tissue and blood from the vagina B 8. implantation C 9. menstruation A 10. semen D. Chemical made in one part of the body that travels in the bloodstream to other parts E. The process that produces the three cell layers of the embryo F. Type of gland that releases its chemicals directly into the bloodstream G. Type of gland that releases its chemicals out of the body For Questions 11–18, complete each statement by writing the correct word or words. 11. After eight weeks of development, an embryo is called a fetus . 12. The gland that produces hormones that regulate the secretions of other glands is the pituitary gland. 13. Cells with receptors for a particular hormone are called 14. A fertilized egg is called a Prostaglandins 15. zygote target cells. . are also known as “local hormones.” 16. Oxygen and nutrients diffuse from the mother’s blood to the embryo’s blood through the placenta . 17. The early stages of the brain and spinal cord form during neurulation . 18. Sperm are produced in ducts called the seminiferous tubules. Chapter 34 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 542 Name Class Date In the Chapter Mystery, you learned about what happens when the body is not given everything it needs. Nonessential life processes, such as menstruation, may stop. In addition, the body may begin to take nutrients from organs and tissues. OUT OF STRIDE Learning Giving Your Body What It Needs There are many diseases associated with undernutrition. In this country, most undernutrition diseases and disorders are associated with psychological issues rather than a lack of available nutrients. One of the most common of these diseases is anorexia nervosa. This is part of the FAQs page on a Web site about anorexia nervosa. FAQS About Anorexia Q: What is anorexia nervosa? A: Anorexia nervosa is a medical condition that affects how a person thinks about food and about his or her own body. Return to Top Q: Does anorexia affect only girls and women? A: It’s true that 90–95% of anorexics are female, but that means that 5–10% are boys and men. Return to Top Q: What causes anorexia? A: We don’t know. We don’t even know if there is one cause or many. But there are risk factors. Return to Top Q: What are the risk factors? A: The first is culture. Anorexia almost exclusively affects people who grew up in or moved to Western cultures where they were exposed to images of the “ideal” body type for their sex. For example, Western media is full of images of flawless, thin women. Having a relative with anorexia makes it more likely a person will develop it. It’s possible that personality traits and genetic factors are involved as well. Return to Top Q: What effect does anorexia have on the human body? A: The symptoms of anorexia vary depending on the severity and length of time the person has suffered from the disease. Anorexia changes the brain chemistry, causing irritability, moodiness, and difficulty thinking. The hair and nails become brittle. The blood pressure goes down and the heart rate slows. The skin becomes dry and bruises easily. Bones lose mass and break more easily. Other symptoms include kidney stones and kidney failure, anemia, yellowing of the skin, and the growth of fine hairs over the entire body. In women, anorexia stops the menstrual cycle and increases the possibility of miscarriage and low birth weight. Return to Top Continued on next page ▶ Chapter 34 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 543 Name Class Themes Date Science and Health Literacy 1. What percentage of anorexics are male? 5–10% 2. What parts of the body are affected by anorexia nervosa? The brain, hair, nails, heart, skin, bones, kidneys, blood, and in women at least, the reproductive system 3. What symptoms are described both in this FAQ and in the solution to the Chapter Mystery? Stopping of the menstrual cycle and bones losing mass and breaking more easily 4. What do you think some of the treatments for anorexia might be? SAMPLE ANSWER: First, the patient would be fed a nutrient-rich diet under supervision. The patient would then receive psychiatric care in order to treat the underlying causes of the disease. 5. Suggest some ways in which the incidence of anorexia nervosa in the United States might be decreased. SAMPLE ANSWER: Encourage advertising agencies, magazine publishers, cosmetic and clothing companies to use models with a wide variety of body types. Have media give coverage to female athletes, politicians, businesswomen, and other role models that do not fit the mainstream idea of the ideal feminine form. Help Wanted: Nutritionist The skills used in this activity include communication skills, creativity and intellectual curiosity, interpersonal and collaborative skills, accountability and adaptability, and social responsibility. An interest in nutrition could lead to a career as a nutritionist or a dietician. Nutritionists and dieticians work in hospitals, nursing homes, medical offices, schools, governmental agencies, and any number of other places. Use library or Internet resources to research the various job opportunities that involve nutrition. Then write up a help wanted ad that describes your ideal job. Compare your ad with those of your classmates. Students’ ads should describe the job and the qualifications required for the job. Chapter 34 • Workbook A • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved. 544