Module 3S1 Reproductive Systems

Unit 2 - Reproductive Systems

The concept organizer shows the relationships among the reproductive structures, hormones, and development. A mammalian reproductive system that functions properly is needed for a healthy body and to produce a healthy family. This will then lead to the continuation of the species. In the concept organizer, the unit inquiry indicates how reproductive systems, hormones, and development are required to produce healthy offspring. The importance of how reproductive technologies affect all areas is shown, as well as the transmission of sexually transmitted infections (STIs). You may find it beneficial to refer to this concept organizer as you work through the unit; it can function as a study guide.

Module Descriptions

Module 3: Section 1—The Male and Female Reproductive Systems

In this section of Module 3 you will examine both the male and female reproductive systems, learning the structures and their functions involved to produce the sex cells, or gametes. You will learn about the difference between primary and secondary sex characteristic and be able to compare and contrast the sperm and egg. Finally, you will study how sexually transmitted infections may affect reproductive systems and a developing fetus.

You will be asked to apply your knowledge to answer the following question:

• What are the structures of the male and female reproductive systems, and how do these structures function to ensure the survival of the human species through reproduction?

Module 3: Section 2—Reproductive Hormones

In this section of Module 3, you will learn how hormones regulate the both the male and female reproductive systems. You will study, in males, how the hormone feedback system, initiates puberty, maintains a constant level of function through the reproductive years, and causes change in the aging process.  You will examine, in females, the detailed hormonal control of the monthly menstrual cycle, the consequences to the cycle whether or not fertilization has occurred, and the hormonal action that results in menopause.

At the end of this module, your knowledge should allow you to answer the following question:

• How is the homeostasis of reproduction maintained by hormones in the male and female?

Module 4—Human Development

In this module you will learn about the process of human development. You will go through the key development periods of fertilization, cleavage, implantation, cell differentiation, placenta, and fetal development to the outcome of birth. You will examine substances and conditions that can affect normal embryonic and fetal development. Lastly, you will focus on reproductive technologies—those that prevent and enhance reproduction potential and the ethical, moral, legal, and personal issues that surround them.

Through completion of this module, you will be able to answer the following question:

• What is normal embryonic and fetal development and how can genetic, hormonal, and environmental effects affect this development?

Unit Intro

It is amazing how humans have managed to sustain their existence and dramatically increase their population on a planet that is constantly changing. One of the main reasons this has been possible is through sexual reproduction.

In this unit of Biology 30 you will investigate the human reproductive system as a representative mammalian system responsible for reproducing the organism and carrying on the species. You will learn about the structures and the functions associated with human reproduction and the hormones that regulate reproduction, development, and establish homeostasis. You will also study how environmental factors have an influence on embryonic and fetal development. Finally, you will examine various types of reproductive technologies.

In past studies you discovered that all living organisms come from other living organism and that a characteristic of “living things” is that, as living organisms, they are able to reproduce. Although reproduction is not necessary for survival at the individual level, reproduction is necessary for the survival of the species. Reproduction produces new individuals of a species, either identical to or a variation of the parent(s).

In Biology 20 you started looking into how body systems work together to maintain homeostasis. You will continue your study by examining the reproductive system. You will use your understanding of the nervous system and endocrine systems to further explore how they contribute to maintaining equilibrium within the reproductive system and to the homeostasis of the body. You will develop a deeper understanding of the structures and functions of your own reproductive system and those of the opposite sex. This exploration will help you develop an appreciation for the miracle of life—from conception, through development, to birth.

There are two modules in Unit B. Module 3 has been divided into two sections. In Module 3: Section 1 you will study the structures of the male and female reproductive systems, how they function, and how they can be adversely affected by STIs (sexually transmitted infections). Module 3: Section 2 is dedicated to helping you understand how hormones in the male and female maintain homeostasis of reproduction. Module 4 will focus on the development of offspring from fertilization to birth, how cells differentiate to perform certain functions, and how development is regulated by genetic, endocrine, and environmental factors. Together, the modules will support your inquiry into how humans have managed to sustain their existence and increase their population on a planet that is constantly changing.
 

You will specifically be able to

• explain how species survival is ensured through reproduction
• identify and describe the structures and functions of the human reproductive systems
• explain how human reproduction is regulated by chemical control
• describe how cell differentiation and development are influenced by genetic, endocrine, and environmental factors
• analyze how sexually transmitted infections and reproductive technologies can prevent or enhance fertility

Big Picture

As a young adult heading into your reproductive years, you are not often asked if you are planning to propagate your species. However, having a baby definitely contributes to the continuation of the human species by adding one more body to the population of the world.

You may or may not have considered whether your future will include your own children. That is a personal decision. When you do consider your future you may be faced with questions such as the following:

• Do you want to have children? Why or why not? How many?
• At what age to you want to start your family?
• Are there decisions or medical conditions that can impact your ability to conceive a child?

Some sexually transmitted infections and childhood illnesses can cause fertility problems later on in life. Diseases such as the mumps can cause infertility but can be avoided altogether if you were immunized against mumps as a child.

 As a young adult it is often difficult to look into the future to see whether problems might arise because of parental or personal choices made in childhood or youth. Although you cannot change the past, being informed can help you make better choices today and in the future.

If you are to suffer problems with fertility, this will make your personal choices around having a family more difficult, as well as your potential role in the continuation of the human species.

Couples with infertility issues can face a daunting journey from diagnosis through to treatment. This module will give you further information about the three couples facing fertility issues that you will follow throughout the unit. As their fertility doctor you will have to work with these three couples on their fertility problems. You will try and discover their fertility issues through their history and physical exam results, (finding the problem(s)), diagnosis (identifying the cause of the problem(s)), and consultation (discussing the problem(s)). You will guide the couples through their fertility issues from conception to the birth of their child. You can review the information about these couples by reading "A Fertility Case Study." You will collect more information on each couple and their fertility challenges as you work through the lessons to complete the unit assessment.

The introduction to these couples and the work you do in this module will help you understand how the structures of the male and female reproductive systems function and their role in ensuring the survival of the human species through reproduction.

You will explore the following essential questions:

• What are the structures and functions of the male and female reproductive systems?
• What are the functional units of the male and female reproductive systems?
• How are the functional egg and sperm supported and nourished through to their development?
• What genetic factors and hormonal influences are there on the formation of the gonads and reproductive organs in the male and female embryo and fetus?
• How can sexually transmitted infections (STIs) interfere with fertility and reproduction?
• How do social, cultural, environmental, ethical, and economic perspectives apply to decisions regarding the use of any scientific or technological developments?

Module 3 - Reproductive Systems

Introduction

© 2008 Jupiterimages Corporation

As you experienced the wild ride of puberty, you probably gained some personal knowledge about the unique features in both males and females that support sexual reproduction. These structures are specialized to perform unique functions to ensure production of the next generation and survival of the human species. You may already think that you know the differences between the male and female reproductive systems but, in this module, you will discover other structures that are unique and suited to perform specialized functions. Finally, you will study how sexually transmitted infections can affect the reproductive systems and possibly a developing fetus.

To understand how the human species has managed to increase its population on a constantly changing planet, you will examine the human reproductive systems. This module is split into two sections. In this first section you will examine the structures and functions of the human reproductive systems and the implications of sexually transmitted infections on fertility.

Since the module is split into two sections, the module assessment will also be split. The Section 1 Assessment will evaluate the reproductive systems and the Section 2 Assessment will evaluate hormone control of the reproductive systems.

In addition to the module assessments, you will be re-introduced to the three couples struggling with infertility who make up the fertility case study for the unit assessment.

Lesson 2.3.1S1

Lesson 1—The Human Male Reproductive System

Get Focused

Choices you make in your life are not always yours alone. When you were a young child, your parents and loved ones made many important choices for you. One of the choices they made was to decide whether or not you should be immunized against certain diseases.

You may remember the concept of antibody-mediated immunity from an earlier biology course. The body forms antibodies (proteins) to recognize, neutralize, and destroy foreign substances. In childhood immunization programs, children are given vaccines designed to stimulate the body’s defense mechanism into fighting off certain contagious diseases. If allowed to develop, some of these contagious diseases can have severe consequences to reproductive health. Do you know what immunizations you received as a child?

Nineteen-year-old Tim’s parents decided not to immunize him with the MMR (Mumps, Measles, and Rubella) vaccine when he was a child. He developed a severe case of mumps. The mumps led to orchitis—very painful swelling of the testicles.Orchitis affects one in five adult men and its symptoms can lead to infertility. This could be devastating to Tim later in life. Orchitis could cause so much damage to his reproductive structures and their normal functions that Tim may not be able to father children. You can learn more about Tim’s condition using the term “orchitis” in an Internet search.

Infertility is on the rise in North America. If infertility rises significantly at a global level, the continuity of the human species could be affected. Some couples are infertile because of structural or functional issues with one partner’s reproductive system.

In Lesson 1 you will investigate the male reproductive system and many issues that affect male fertility. You will investigate the following focusing questions:

• What are the main structures and functions of the male reproductive system?
• How do these structures support continuity of the human species?
• What is the functional unit of the male reproductive system?

Module 3: Section 1 —Lesson 1 Assignment

Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio30 2.3.1S1 online assignment

Here is a tutorial video for this lesson that you can watch if it suits your learning style.  

2.3.1 page 2

Explore

Video: 

Crash Course - Reproduction

Read

Your own reproductive health is not only important to you; it may also be important to your future partner. Therefore, it is important that both males and females understand the structure (anatomy) and function (physiology) of the male reproductive system, including its primary reproductive organs, ducts, and accessory glands. Read pages 478–481 of the textbook. Summarize what you read by taking notes, completing a chart or table, or recording the information in another way. You must include a labeled diagram of the male reproductive system in your notes. Save your work in your course folder.

Self-Check

Watch and Listen

Watch the video clip “The Male Reproductive System: Perpetuating the Species ” to further your understanding of the male reproductive system. The video clip helps you to see another view of the structures involved in the male system.

The Male Reproductive System

The Male Reproductive System:

1. What are the three characteristics that set the reproductive system apart from other body systems?
2. What is the importance of sexual reproduction?
3. What is the goal of reproduction?
4. What are the three factors that have led to fewer eggs and increased survival rate of offspring in vertebrates?
5. What are the functions of the male reproductive system?
6. List three unique features of a sperm cell.
7. How many sperm are needed to fertilize an egg?
8. How many sperm are released in one ejaculation?
9. What accounts for the difference in size between the egg and the sperm?
10. Where are the sperm produced?  
11. What is the name of the sack that holds the testes?  
12. Why are the testes held outside the body?
13. What is the ideal temperature for producing sperm?
14. What is the difference between the testes and the testicles?
15. How do the testicles maintain a constant body temperature?
16. What is inside the testes?
17. How long does it take to produce a sperm?
18. What is the epididymis?
19. How long do sperm survive at body temperature?
20. What is the name of the structure that sperm travel through when leaving the testes?
21. Sperm are sensitive to acidic conditions. Where might sperm encounter acidic conditions?
22. What are the characteristics of seminal fluid?
23. List the structures involved in seminal fluid production and what each structure contributes to the process.
24. List the structures inside the testes and the function of each.
25. What provides a source of energy for sperm?
26. How does the nervous system play a role in the male reproductive system?
27. What structure delivers sperm to the egg?

2.3.1 page 3

Reflect and Connect

Sperm Pathway, Orchitis

Think back to nineteen-year-old Tim who developed a severe case of mumps, which led to orchitis. How might orchitis affect his reproductive system? Assume that Tim is not very aware of his own reproductive system. As a friend, you will use what you have learned in this lesson to help Tim understand his reproductive system, orchitis, and the effects the condition may have on the structures and functions of the male reproductive system.

Module 3: Section 1—Lesson 1 Assignment

There are two parts to this assignment. Answer each part through a detailed illustration or diagram, PowerPoint presentation, video, cartoon, animation, written report, podcast, or any other form approved by your teacher. You may respond through a different form for each of the two parts.

Retrieve your copy of Module 3: Section 1—Lesson 1 Assignment that you saved to your computer earlier in this lesson. Complete the Reflect and Connect questions. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Discuss

Write a paragraph to respond to two of the questions below (one paragraph per question). Post your responses to the discussion area for your class. Read the responses of at least two other students. If possible, discuss the responses amongst yourselves.

• What does being male mean to you? Is it just about anatomy and hormones?
• What are some of the threats to a healthy male reproductive system? Which threats can you control? How can you deal with the threats that are out of your control?
• What are the implications of a lower sperm count in North American men?
• What are the implications of a low or reduced fertility rate in North America

Build on what you know about the male reproductive system by finding out what can be done if something goes wrong with its structures or functions. You can do further research on the twelve main male reproductive structures to find a dysfunction that can occur with each one, and a treatment to overcome each dysfunction.

Module 3: Section 1—Lesson 1 Assignment

Submit your completed Module 3: Section 1—Lesson 1 Assignment to your teacher for assessment.

Lesson Summary

In Lesson 1 you investigated the following focusing questions:

• What are the main structures and functions of the male reproductive system?
• How do these structures support continuity of the human species?
• What is the functional unit of the male reproductive system?

The male reproductive system is designed to produce and release large numbers of sperm. The gametes (sperm) are produced in the gonads (testes), within the seminiferous tubules where the temperature for proper sperm development is controlled by the scrotum. There the developing sperm are supported by the Sertoli cells and are transferred to the epididymis to be matured and stored.

During an ejaculation event, the ductus deferens helps transfer the sperm from the testes to the urethra, picking up the semen or seminal fluids on the way. The seminal fluids help the sperm in providing sugar for energy, alkalinity to neutralize urine and vaginal acids, and a medium for motility. Semen leaves the male body through the penis. The male reproductive system and sperm structure allow for sperm to be deposited into the female and to move through the female reproductive system.

Childhood illnesses, sexually transmitted infections, structural problems, and environmental and societal factors can all interrupt the function of the male reproductive system. The end result of sexual reproduction is the formation of a fertilized egg that contributes to variation and continuation of the human species.

Lesson 2.3.2S1

Lesson 2—The Human Female Reproductive System

Get Focused

In Lesson 1 you learned about the important role the male reproductive system plays in the continuation of the human species. While a vital contributor to reproduction, the male cannot reproduce by himself. To understand how the human species is perpetuated, it is vital to understand the other half of the equation—the structures and functions of the female reproductive system. It is the female reproductive system that forms, develops, and delivers a new human organism to functional independence as a newborn baby. This is a complex process that requires all parts of the female system to work in synchronicity.

During puberty, the female reproductive system undergoes many changes. Top amongst these changes for most young women is menarche, the start of menstruation. Menstrual cramps, mild to severe pressure or pain experienced in the abdominal and pelvic areas, are an unpleasant symptom of menstruation for many young women.

Estimates suggest that 50% of women suffer from cramping, with up to 15% of these women defining their menstrual cramps as severe. The medical term for painful menstrual cramps is dysmenorrheal. Women who have chronic cramping may or may not have trouble with fertility.

In addition to the pain experienced in the abdomen and pelvis, menstrual cramps can be associated with one or more of the following ailments: headaches, nausea, vomiting, constipation, or diarrhea. You may have seen advertisements for over the counter menstrual medication to help alleviate some of these symptoms.

Update: A Fertility Case Study

In Lesson 2 you will investigate the female reproductive system and many issues that affect female fertility. You will investigate the following focusing questions:

• What are the essential structures and functions of the female reproductive system?
• How do these structures support continuity of the human species?
• What is the functional unit of the female reproductive system?

Module 3: Lesson 2 Assignment

Once you have completed all of the learning activities for this lesson, you can complete the online lesson.

Bio30 2.3.2S1 online assignment

Here is a tutorial video for this lesson that you can watch if it suits your learning style.  Bio30 tut#2.3.2S1

** The Self-Check and Try This questions in this lesson are not marked by the teacher; however answering these questions will help you review important information and build key concepts that may be applied in future lessons. You can respond to these mentally, write out your response, or record your answer in any other way that works for you.

2.3.2S1 page 2

Explore

You will complete a Read and a Watch and Listen activity. Choose which activity you would like to complete first, but make sure you complete both activities.

Read

Like males, females must maintain good sexual health. Because both partners’ ability to reproduce depends on the female reproductive system, it is important that both males and females understand the structure and function of the female reproductive system. Read textbook pages 481–484 of the textbook. Summarize what you read by taking notes, completing a chart or table, or recording the information in another way. You must include a labeled diagram of the female reproductive system in your notes.

You may answer questions 1–8 on page 485 of the textbook. If you choose to answer these questions, you do not have to answer the question sheet in the next exercise.

Save all of your work from this Read activity in your course folder.

Self-Check

Watch and Listen

Watch the video clip about the Female Reproductive System to further your understanding of the female reproductive system.

1. What is another name for the egg produced by the female reproductive system?
2. What are the three functions of the female reproductive system?
3. What is the name given to the female gonads and what is their function?
4. Describe the hormonal control of the ovaries.
5. How is an egg transported from outside the ovary to the uterus?
6. What is the function of the uterus?  
7. What is the name of the inner lining of the uterus?
8. What is the difference in structure between the outer and inner walls of the uterus?
9. What is the function of the vagina?
10. What is the term given to the female external genital organs?
11. What structures does the vulva include?  
12. What is the name and function of the glands found on either side of the vaginal opening?
13. What is the size and function of the ovaries?
14. When does a female start producing egg cells?
15. Describe the type and number of egg cells that are present at birth in a female baby.
16. How many oocytes will mature in a female?
17. What is the name given to the process of forming female gametes?
18. Describe what is happening to the development of the female gamete before and after the onset of puberty.
19. How many oocytes mature each month during a woman’s reproductive cycle?
20. What happens when eggs mature? 

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2.3.2S1 page 3

Reflect and Connect

Egg Pathway

Think back to Sarah and her condition of dysmenorrheal. Imagine that you are a sexual health nurse who is helping Sarah and her mother address Sarah’s menstrual cramps. It is important for you to explain, in appropriate language, what Sarah and her mother need to know to make an informed choice regarding treatment options.

Module 3: Section 1—Lesson 2 Assignment

Retrieve your copy of Module 3: Section 1—Lesson 2 Assignment that you saved to your computer earlier in this lesson. Complete all questions through a detailed illustration or diagram, PowerPoint presentation, video, cartoon, animation, written report, podcast, or any other form approved by your teacher. You may respond through a different form for each of the two parts. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Discuss

Write a paragraph to respond to two of the questions below (one paragraph per question). Post your responses to the discussion area for your class. Read the responses of at least two other students. If possible, discuss the responses amongst yourselves.

• What does being female mean to you? Is it just about anatomy and hormones?
• What are some of the threats to a healthy male reproductive system? Which threats can you control? How can you deal with the threats that are out of your control?
• What are the pros and cons of postponing having children to pursue other goals?
• Can a woman who only has a left ovary and a right Fallopian tube become pregnant? Why or why not

Going Beyond

Build on what you know about the female reproductive system by finding out what can be done if something goes wrong with its structures or functions. You can do further research on the main female reproductive structures to find a dysfunction that can occur with each one, and a treatment to overcome each dysfunction.

Module 3: Section 1—Lesson 1 Assignment

Submit your completed Module 3: Section 1—Lesson 2 Assignment to your teacher for assessment.

Lesson Summary

In Lesson 2 you investigated the following focusing questions:

• What are the essential structures and functions of the female reproductive system?
• How do these structures support continuity of the human species?
• What is the functional unit of the female reproductive system?

The female reproductive system is designed to produce a very limited number of gametes. The female gonads (ovaries) produce the egg (ovum), the functional unit of reproduction for the female. An egg is further matured inside a follicle, within an ovary. Once matured, the egg, through the process of ovulation, ruptures out of the ovary. Outside of the ovary, the fimbriae pick up the egg and sweep it into the oviduct or Fallopian tube. With the help of cilia and muscle contractions in the oviduct, the egg is transported to the uterus. If sperm fertilizes the egg in the oviduct, the resulting zygote may implant in the uterus resulting in the development of a new human life. If a sperm does not fertilize the ovum, the ovum is transported out of the uterus with the shedding of the endometrial lining through the cervix and vagina to the outside of the body during menstruation.

Because only a limited number of gametes are produced, protection of the egg and the developing embryo is critical. Their protection is ensured by internal fertilization and development. The female reproductive system is one half of the equation that brings a new human life into the world and contributes to the continuation of the human species.  

Lesson Glossary

dysmenorrheal: severe menstrual cramps

menarche: a female’s first menstrual cycle

menstruation: the monthly shedding of the endometrial lining

Lesson 2.3.3S1

Get Focused

In order for reproduction and perpetuation of the species to occur, functional gametes must be formed. To form functional gametes, supporting structures must help develop and protect the sperm and egg cells. For most couples these structures function as they should. However, for some couples these supporting structures do not function well or at all, and problems with fertility can occur. Ultimately, infertility is a result of an abnormality in either the sperm or the egg, or the body’s ability to support conception to birth.

A sperm analysis determines certain characteristics of semen and the sperm contained within the semen. An abundance of abnormalities with the sperm can result in a reduced fertility rate. Sperm must be developed correctly to successfully complete their function of fertilizing an egg cell. To gain a better appreciation of what a sperm analysis examines and how its findings indicate fertility issues, it is important to understand how gametes, both sperm and egg cells, are developed.

In Lessons 1 and 2 you learned that sperm, the functional unit of the male reproductive system, are developed and matured in the testes and that the ovum, the functional unit of the female reproductive system, is produced and matured in the ovaries. In Lesson 3 you will further your understanding of gametes development—first the sperm and then the ovum. You will investigate the following focusing questions:

• How do sperm and egg cells develop into functional gametes?
• What supporting structures help in the development of a fully functional gamete?

Module 3: Section 1—Lesson 3 Assignment

     Once you have completed the learning activities for this lesson, you can complete the online assignment.

Bio30 2.3.3.S1 online assignment

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Here is a tutorial video for this lesson that you can watch if it suits your learning style.  Bio30 2.3.3S1 Gamete Development

2.3.3S1 page 2

Explore

This section is divided into two parts: spermatogenesis—formation of sperm and the structures that support sperm production; and oogenesis—the formation of the ovum and the structures that support its development.

Spermatogenesis

While women are born with all the eggs they will ever have, men produce sperm on a continual basis. A man’s sperm or gamete development can therefore be affected by what he does daily. Choices a man makes regarding smoking, stress management, nutrition, exercise, and drug and alcohol use contribute to the production and quality of his sperm. Regardless of the choices he makes, the quality of a man’s sperm begins to slowly decline at approximately age 25.

In the early stages germ cells or gametes are supported, nurtured, and protected by specialized supporting somatic cells. Mature gametes are produced in a process called gametogenesis and developed in a process called spermatogenesis. Throughout spermatogenesis mature male gametes commonly called sperm are scientifically referred to as spermatozoa. During the stages of development the sperm cells are in close contact with Sertoli cells and interstitial cells.

Sertoli cells are found in the testes, within the seminiferous tubules, and are sometimes referred to as nurse cells. They nurture the developing sperm cells by providing secretory and structural support. The Sertoli cells give structural support by acting as a barrier to protect the sperm during their development. Since spermatozoa start development at puberty, the body considers sperm cells to be foreign to the body. If not protected by the Sertoli cells, the body’s immune system would destroy them. By producing the hormone inhibin, Sertoli cells perform a secretory function. Inhibin targets the anterior pituitary and hypothalamus to inhibit the production of follicle stimulating hormone (FSH).

Interstitial cells are found in the testes but are not found in the seminiferous tubules. While they are therefore only indirectly linked to sperm production, they do secrete testosterone which targets the entire male body and stimulates the development of the male reproductive system, the secondary male sex characteristics, and spermatogenesis.

Read

Reread section ”The Testes” on pages 479 and 480 of the textbook. Focus on information about the supporting structures of the gametes.

To gain further information, do an Internet search using the search terms “Sertoli cells” and “interstitial cells.”

Watch and Listen

Watch the section on spermatogenesis in the video to further your understanding of how the structural support tissue helps develop the male gametes. Take notes on the information you learn in this video and save them in your course folder.

Oogenesis

In females, the germ cells or gametes are the egg cells. The process of developing mature egg cells is called oogenesis. Follicle cells are the structural supporting cells that surround and develop the egg.

Egg cells begin as oogonia and then develop into primary oocytes. About 700 primary oocytes are formed in the ovaries during fetal development. The primary oocytes stay dormant in the female body until the beginning of puberty. At the onset of puberty some of the primary oocytes will further develop into functioning egg cells, generally at a rate of about one per month. While in the ovary, each primary oocyte is surrounded by follicle cells. Together the primary oocyte and the follicle cells surrounding it are referred to as the primary follicle.

Like Sertoli cells, the follicle cells perform a secretory and structural support function for the developing gamete. The follicle cells give structural support by fully surrounding the egg, thereby helping to nourish and protect the primary oocyte. The follicle cells give secretory support by releasing estrogen and some progesterone.

When chemically stimulated to do so, the primary follicle helps develop the primary oocyte into a secondary oocyte and then into a fully functioning mature egg or ovum. Ovulation takes place when the fully matured egg is expelled from the ovary.

The support of the follicle cells and Sertoli cells help ensure properly formed gametes, which can then combine during fertilization to form an embryo, thus continuing the species.

Read

Reread section “The Ovaries” on page 482 of the textbook to review the process of oogenesis. This section of the textbook does not present much information on the role of the follicle cells. To gain further information, do an Internet search using the search term “follicle cell.”

Watch and Listen

Watch the section on oogenesis in the video clip to further your understanding of oogenesis and the role of the follicle cells. Take notes on the information you learn in this video and save them in your course folder.

2.3.3S1 Lab

Module 3: Section 1—Lesson 3 Lab

Examining Gonads and Gametes

Although the testes and ovaries are quite different structures, they serve the same two basic functions:

• development of gametes

• secretion of sex hormones

In this investigation you will compare ovarian and testicular tissue using microscopy (scientific term for objects viewed by a microscope) images provided, in an effort to identify the supporting structures that help develop the egg and sperm cells.

Retrieve your copy of Module 3: Section 1—Lesson 3 Assignment that you saved to your computer earlier in this lesson.

Complete the three drawings and three questions in your Assignment document when instructed to do so as you complete this lab. When complete, save your assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

This lab is similar to the one on page 483 of the textbook. However, because you may not have a microscope, the microscope slides will be provided to you. The procedure has been rewritten to guide you through the lab using the microscopic images.

Problem (Purpose)

How do the structures of testicular and ovarian tissues relate to their biological functions?

Materials - Use the images below as your microscope slides.

• blank paper
• pencil
• microscopy images of testis, 100X, 200X, 400X (provided below)
• microscopy images of cat follicle, 100X, 200X, 400X (provided below)

Procedure

Part 1—Testicular Tissue

1. View the microscopy and other model images of the testes below. Where it is provided, pay attention to the magnification power given.
2. Read “Appendix D: Review of Biological Drawings” on page 759 of the textbook. Follow the instructions given when making the biological drawings requested in this lab.
3. Search the Internet for images of the internal structure of the testes. You could start your search using the phrase, "seminiferous tubules male reproductive system anatomy." Use results from medical schools to study the internal structures.
4. Examine the microscopy images provided below. Look for several circular structures. These are the seminiferous tubules. Try to identify the following cells in the images: lumen, seminiferous tubule wall, spermatogonial cells, spermatocytes, spermatids and spermatozoa or mature sperm cells, Sertoli cells, and interstitial cells.

5. Draw a diagram of the specimen as it appears under the highest power magnification. Label the following cells in your drawing: lumen, seminiferous tubule wall, spermatogonial cells, spermatocytes, spermatids and spermatozoa, Sertoli cells, and interstitial cells. If possible, paste your image into your Assignment document; otherwise submit your drawing to your teacher when instructed to do so later in this lesson.                

Part 2—Ovarian Tissue

1. View the microscopy and other model images of the ovaries below. Where it is provided, pay attention to the magnification power given.
2. Search the Internet for images of the internal structure of the ovary. You could start your search using the phrase, "human female reproductive system histology." Use results from medical schools to study the internal structures.
3. Examine the microscopy images provided below. Look for larger circular structures; these are developing egg cells. Try to identify the following structures in the images: primary follicle, primary oocyte, mature follicle, mature ovum, ovarian tissue, and corpus luteum.

Microscope images of a cross-section of a cat ovary showing a primary follicle at 100X magnification

4. Draw a diagram of the specimen image, Cat, Primary Follicle, 100X. Label the following structures in your drawing primary follicle, primary oocyte, ovarian tissue, and corpus luteum. If possible, paste your image into your Assignment document. Otherwise, submit your drawing to your teacher when instructed to do so later in this lesson.   
5. Draw a diagram of the specimen image, Cat, Mature Follicle, 100X. Label the mature oocytes and follicle cell structures in your drawing. If possible, paste your image into your Assignment document. Otherwise, submit your drawing to your teacher when instructed to do so later in this lesson.

Observations

After examining the microscopy slides of testicular and ovarian tissues, you should have completed three diagrams with appropriate labels and titles. You should now be able to identify the functional gametes as well as their supporting structures.

Questions

Answer the questions in the Module 3: Section 1—Lesson 3 Assignment document using knowledge from examining the gonad tissue sample images.

Conclusions

In this lab you identified the location and function of the gonads, gametes, and their supporting structures. Reproduction, and therefore continuation of the species, would be impossible if not for proper functioning of the supporting cells that develop the gametes.

Real World Applications (Going Beyond)

In this lab you have seen gonad tissue and identified some of the structures within these organs. Things are never quite as simple as they seem; there are other structures that have not been mentioned in this lab or in your textbook. See if you can research and add the following structures to your diagrams: testicular basement membrane, blood-testis barrier, blood vessels, early spermatid, late spermatid, corpus albicans, early and mature corpus luteum, primordial follicles, follicular cavity, follicular fluid, zona pellucid, and corona radiate.

Self-Check

Complete “Section 14.1” questions 1–4 and 6–8 on page 485 of the textbook to see how well you understand the development of the egg and sperm cells.

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Reflect and Connect

Think back to Sam and the semen analysis test he underwent. From your new knowledge of how supporting structures help gametes develop, you can better understand how a semen analysis can contribute to diagnosing an infertility problem.

A semen sample must be analyzed within two hours of being collected. Lab technicians analyze the sample for the following traits:

• Volume: Low volume might suggest an anatomical or functional defect.
• Motility: The quality of spermatozoa movement needs to be forward and progressive and 40 to 60 percent of the spermatozoa needs to be motile.
• Count: A count below 20 million/mL could indicate sterility.
• pH: An increase in the sperm's pH above the normal slightly alkaline state could indicate an inflammation of the prostate.
• Fructose: Absence of this sugar may indicate a possible obstruction of the ejaculatory ducts or seminal vesicles.
• Morphology: Size and shape, only 35% or less of the sperm should have some type of abnormal structure, as seen in the image below.

Sam’s sperm analysis showed a low sperm count. The medical term for this is oligospermia. If you were Sam’s fertility physician you might have considered prescribing a drug called clomiphene, sold under the name ”Clomid.”

Going Beyond

You have been introduced to several disorders in the first three lessons of Module 3. Can you find disorders that are specifically related to the supporting structures like the Sertoli cells, interstitial cells, primary or secondary follicles, and corpus luteum.

Module 3: Section 1—Lesson 3 Assignment

Submit your completed Module 3: Section 1—Lesson 3 Assignment to your teacher for assessment.

Lesson Summary

In Lesson 2 you investigated the following focusing questions:

• How do sperm and egg cells develop into functional gametes?
• What supporting structures help in the development of a fully functional gamete?

Human reproductive systems are uniquely designed to develop properly functioning gametes thereby ensuring continuation of the human species. In the male reproductive system, the male gonads (the testis) produce the functional gametes (the sperm) in the seminiferous tubules. The Sertoli cells give both structural and secretory support to the developing sperm. Structural support is provided by protecting the developing sperm from the body’s immune system, and secretory support is provided by secreting the hormone inhibin. The interstitial cells, also found in the seminiferous tubules, indirectly support sperm production by secreting the hormone testosterone. Testosterone then stimulates the process of spermatogenesis to develop the sperm.

The female gamete, the egg, is produced in the ovary and provided with structural and secretory support. Follicle cells provide structural support by surrounding the primary oocyte helping to nourish, protect, and develop the egg cell. Follicle cells also offer secretory support by releasing estrogen and some progesterone. These hormones then help to develop the primary oocyte into a mature egg ready for ovulation.

Continuation of the species is ensured when these two properly formed gametes are joined through fertilization.

Lesson Glossary

oligospermia (also known as oligozoospermia): a condition in which there are less than 20 million spermatozoa per mL of semen

Lesson 2.3.4S1

Lesson 4—Chromosome and Hormone Influence

Get Focused

The first couple in “A Fertility Case Study” is Jane and John. They did not decide to have children until they were in their early thirties. Their first pregnancy produced gender-different twins, also called fraternal or dizygotic (di = two, zygotic = zygote) twins. Gender is dependent on the chromosomal make-up of the embryos. In fraternal twins, each embryo has a unique make-up because it comes from a separate egg fertilized by a separate sperm.

To maintain the variation and continuation of a mammalian species, such as the human species, two separate genders are required. In a species with two genders, there are two different sex chromosomes at play—the X and Y chromosomes. These are referred to as sex chromosomes because they determine the gender, or sex, of the offspring. To be a male, an organism must have one X and one Y chromosome (XY). To be a female, an organism must have two X chromosomes (XX). Further information on the structure and function of chromosomes will be provided in Unit C.

The gender of a child is determined at conception by the genetic material carried in the sperm. While all eggs carry the X chromosome, a sperm can carry either an X or a Y chromosome. Although it was once believed that female development would just occur unless ‘maleness’ is stimulated by the presence of the Y chromosome, researchers now think the process of becoming female is much more intricate.

While the genders of Jane and John’s twins were determined at conception, they remained identical in gender until about the sixth or seventh week of their embryonic development. At this point, the sex-determining region Y (SRY) carrying the testis-determining factor (TDF) gene found on the Y chromosome of their male fetus, began the process that leads to the sexual development of a male individual. The TDF gene started the production of the male sex hormones, collectively called androgens, which began the development of the male sex organs. The lack of the Y chromosome with the TDF gene and the resulting male sex hormones allowed the other fetus to develop as female.

To develop the male twin, the TDF gene caused differentiation of the supporting cells into Sertoli and interstitial cells. The interstitial cells begin to form the hormone testosterone by about the eighth week of gestation. From the eighth to the twelfth week of gestation, the testosterone caused the gender identical structures to differentiate into male structures—such as testes, penis, and scrotum. Although the way in which an embryo becomes female is not fully understood, it does appear that without the presence of testosterone and other hormones to suppress the development of female sex characteristics, hormones, and reproductive structures develop.

Although the ways in which embryos develop as male or female differ, both are controlled by genes and hormones. For the twins, their genders were determined at conception and developed as they underwent their fetal growth. They will display all of their gender-specific characteristics until they reach puberty. You will learn more about puberty in Module 3: Section 2.

In Lesson 4 you will learn the roles of the X and Y chromosomes and the hormones they produce to better understand gender differentiation and general puberty hormone changes. You will investigate the following focusing questions:

• How is gender determined at conception?

• How do the X and Y chromosomes and hormonal influences form gonad and reproductive organs in the female and male embryo and fetus?

Module 3: Section 1—Lesson 4 Assignment

There is no assignment for this lesson. As the influence of the male and female chromosomes and their hormones is not complete in forming male and female characteristics until after puberty, the assessment for the material presented in this lesson will be included in the Module 3: Section 2 Assignment.

Here is a tutorial video for this lesson that you can watch if it suits your learning style.  Bio30 tut#2.3.4S1

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Read

Read “Sex Hormones and the Male Reproductive System” on pages 492 and 493 of the textbook and “Sex Hormones and the Female Reproductive System” on page 495 to begin your understanding of gender development in the fetus. Further hormonal regulation of sexual development will be dealt with in Module 3: Section 2. You may summarize your reading in a comparative chart to be saved in your course folder.

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Reflect and Connect

From the time a pregnancy is identified, everybody wonders if the developing baby will be a boy or a girl. Normal embryonic sex determination is a complex process requiring that numerous events  take place in the correct order. If all events proceed successfully a “gender-normal” boy or girl will be born.

Your understanding of the development of Jane and John’s twins into one female and one male child should be falling into place.    

Discuss

Choose one, some, or all of the following questions to discuss through the discussion area of your class:

1. What is the advantage of having more than one gender in a species?
2. Historically, women have been held responsible for not producing male children. How has science helped to change this view? Are there places where the historical view is still held?
3. Should gender be tested for at birth? Why or why not?
4. Are there ways to predict whether a pregnancy will result in a boy or girl before the birth?
5. How many sex chromosomes does a platypus have?

Reflect on the Big Picture

For Jane and John, having different gendered twins was a great way to start their family. However, during the twins development into one male and one female embryo, an abnormality developed in the female fetus. She was born with only one X chromosome, a condition called Turner’s syndrome. The explanation for and results of this missing chromosome will be discussed in Unit C.

Keep track of what is happening with Jane and John by recording the information you learned about their experience in your course folder.

Going Beyond

You may have noticed that there are often exceptions to the rule in biological studies. This is the case with respect to the X and Y chromosomes that determine gender. It is possible during gamete formation that the TDF gene can be transferred incorrectly or can be missing altogether. Conduct research to find out how individuals can be male with a genotype of XX and female with a genotype of XY.

Module 3: Section 1—Lesson 4 Assignment

There is no assignment for this lesson.

Lesson Summary

In Lesson 4 you investigated the following focusing questions:

• How is gender determined at conception?
• How do the X and Y chromosomes and hormonal influences form gonad and reproductive organs in the female and male embryo and fetus?

Sexual reproduction is necessary to provide variation in a species. The formation of male and female gender in embryos is a complex process that is influenced by chromosome structure and sexual hormones secreted. Since all eggs carry the X chromosome and the sperm carries either an X or a Y chromosome, the male parent determines gender. Typically, for an organism to be male, it must carry the XY sex chromosomes; for an organism to become female, it must carry the XX sex chromosomes. Once the chromosomal structure of the individual is determined, various hormones continue the sexual development of the embryo.

For a male embryo to develop the SRY region with the TDF gene, a chain of events begins that leads to the production of testosterone and the eventual outcome of a male fetus. Although the process is not fully understood, the chain of events that leads to the development of a female embryo occurs due to lack of testosterone and other male hormones. Ovaries and the hormones they produce lead to the development of a female fetus.

Gender determination begins at conception but continues through to puberty when the final stages of sex determination are completed. Different genders within a species ensure variation and, ultimately, continuation of a species.

Lesson 2.3.5S1

Lesson 5—How Disorders and Sexually Transmitted Infections Affect the Human Reproductive Systems

Get Focused

The lessons in Module 3 have emphasized that continuation of a species is dependent on reproduction. Sexual reproduction, as seen in mammals including humans, offers the highest advantage for continuation of a species because it ensures diversity.

In order for sexual reproduction to occur, there has to be an exchange of body fluids. Whenever there is an exchange of body fluids there is the chance of acquiring an infection. Infections that are transmitted by sexual contact are referred to as sexually transmitted infections or STIs. Names like sexually transmitted diseases (STDs) and venereal disease (VD) are also used to identify this group of disorders. However, the health community prefers the term infection over the term disease because a person can be infected without showing any signs or symptoms of his or her disease. Even a symptom-free person can pass his or her infection on through sexual contact. STIs can also be transmitted from mother to child in childbirth and/or breastfeeding. STIs pose a risk not only to the individual but also to the species as a whole. Just think of the effect of the HIV/AIDS epidemic, especially in Africa.

STIs are not the only threat to the homeostatic reproductive balance affecting fertility. Disorders such as cancers, endometriosis, ovarian cysts, impotence, Pelvic Inflammatory Disease (PID), and Toxic Shock Syndrome can also affect fertility. This course will not cover all of these disorders in detail but will address some of them, cancer for example.

Cancer is a term used to describe a large number of diseases where rapid, uncontrolled cell division occurs. Cancer can affect fertility in two ways: the disease itself may target and damage specific reproductive structures, and the treatment of the disease in other parts of the body can damage reproductive structures and functions. The most common cancers to directly target reproductive structures and affect fertility are prostate and testicular cancers in males; and cervical, ovarian, and uterine cancers in females. Breast cancer, a common cancer affecting both men and women, does not directly affect fertility. Common cancer treatments that affect fertility include certain chemotherapies, bone marrow or stem cell transplants, radiation treatment, and specific types of surgery. Even the future fertility of a child undergoing cancer treatment may be a concern. Cancer does not always mean an end to fertility—there are many, many cancer survivors who go on to have normal reproductive health including having children.

To their surprise, many couples experience fertility problems due to STIs or cancers. Dina and Donald are the third couple in “A Fertility Case Study.” Both were married to other people before marrying each other. Donald has two children from his previous marriage. Although Dina did not bring any children into her marriage with Donald, she had attempted, without success, to have children in her first marriage. Dina and Donald have been trying to have a child together for two years with no success. The typical first set of fertility tests and blood tests have proven that there are no problems with either of their hormone levels.

As their fertility doctor you want to start the next set of tests on Dina. You inform Dina that you want her to have one more blood test—a test that will detect antibodies related to some common STIs. These antibodies can cause Fallopian tube blockage. At first Dina is upset to hear that you suspect she may currently have or have had an STI. She knows very little about them. As her physician, it is your obligation to explain what the blood test will look for and how STIs can affect fertility.

You can uncover a wealth of information on sexually transmitted infections using the search terms “sexually transmitted infections” and “sexually transmitted diseases” in an Internet search.

In Lesson 5 you will explore how disorders, specifically sexually transmitted infections, compromise structural fertility. You will investigate the following focusing question:

• How do diseases and sexually transmitted infections compromise structural fertility?

Module 3: Section 1—Lesson 5 Assignment

There is no assignment for this lesson but you are still responsible to know the material for test purposes.

Here is a tutorial video for this lesson that you can watch if it suits your learning style.  Bio30 2.3.5S1 STD's

2.3.5S1 page 2

Explore

Try This 

Summary of Sexually Transmitted Infections

The first row has been completed as an example.

Read

STIs have plagued humans for thousands of years. They can affect anyone at any time regardless of gender, age, race, wealth, religion, or culture. In order to make informed choices regarding your reproductive health, you must be aware of the main causes and effects for the most common STIs.

This lesson will only address seven of the most common, serious, and rapidly spreading STIs. There are many other STIs, cancers, and other reproductive disorders that can affect fertility. No specific readings will be assigned for cancers that affect fertility in this lesson. You have likely encountered cancers in earlier biology courses and they will be covered again the lesson assignment and in Unit C.

Read pages 486–490 in the textbook to learn how STIs affect human reproductive systems. You can supplement what you learn by reading the pamphlet “STI – Sexually Transmitted Infections” published by the Public Health Agency of Canada.

Self-Check

Examine the following graphs detailing infection rates of certain STIs by age group in Alberta. For each graph write an interpretation of the data presented by examining the age group and rate of infection.

Discuss

Although STIs can be a difficult topic to discuss it is important to make sure you have a good understanding of what they are and how they are transmitted. Use the discussion area of your class to discuss one, some, or all of the following questions:

1. Why is it so difficult for teens and young adults to believe they can acquire an STI?
2. How would you get the message of the seriousness of STIs across to young people?
3. If a person tests positive for an STI, should health agencies have the right and responsibility to inform the individual’s sexual partners? Why or why not?
4. Can the use of a condom prevent all STIs?

Self-Check

See how well you understand STIs by completing “Section 14.2” questions 1–6 on page 491 of the textbook.

Self-Check Answers

Section 14.2: Review Answers

1. Examples of Viral and Bacterial STIs

2. PID (pelvic inflammatory disease) is a disease that occurs in women; it is caused by undetected Chlamydia that has spread to the cervix and oviducts. PID is painful and can lead to the build-up of scar tissue in the oviducts and open sores on the cervix. This may lead to infertility (oviduct damagge) and/or an increased risk of acquiring HIV. Chlamydia and PID also pose risks to babies who come into contact with the disease during birth, including potential respiratory infections and eye infections. PID can also arise if gonorrhea goes untreated.

3. A woman who is infected with an STI can present numerous risks to her baby. Diseases can be passed to the baby through the placenta (e.g., HIV, hepatitis B), during birth (e.g., HIV, genital herpes, Chlamydia, gonorrhea), through breast milk (e.g., HIV).

4. a) A person who is infected with an STI but does not present any symptoms will not visit a doctor for treatment. While they wait, the infection may become more serious, progressing to PID, infections, cancer of the cervix (women), tumors on the vulva, vagina, anus or penis, or infertility.

b) The public health risk of the asymptomatic individual infected with an STI is that they may unknowingly infect other people if they engage in unsafe sex practices or, in the case of pregnant women, pass the STI to their babies.

5. Look for the following key points: Both viral and bacterial STIs have health consequences, the severity of which increases as the infection progresses untreated and depending on the type of infection. It is true that the viral infections cannot be cured, only managed, and there is a high likelihood that death will result with some viral infections (HIV and hepatitis) or that cancer may develop (HPV). Bacterial infections, while curable, are more likely to go undetected, increasing the possibility that they will be spread unknowingly, as well as the possibility that they won't be detected until they have progressed to the more damaging PID, which can cause scarring and infertility, or infect a baby during birth. In addition, many bacterial diseases are becoming resistant to current antibiotics. The consequences of either form of STI make it preferable to avoid both.

6. a) Points supporting the teaching of abstinence: abstinence (from oral, anal, and vaginal sex, and the sharing of needles) is the only way to guarantee the prevention of transmission of STIs. Points supporting the teaching of safe sex practices: students may argue that individuals will engage in sexual practices so it is better to be educated about safe sex practices to avoid transmission of STIs (as well as unwanted pregnancies). Students can evaluate the arguments from an individual point of view, a societal point of view, or even a government viewpoint. It is in the best interest of society and government to teach people about the effects and transmission of STIs so that healthcare does not have to deal with large volumes of transmissions.

b) Health practitioners can design education campaigns that respect the views of those advocating abstinence and safe sex practices by presenting the facts of each and allowing the recipients of the information to make their own decision. This can be done by avoiding nuanced language or judgmental, subjective conclusions.

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Self-Check

As Dina and Donald’s fertility doctor, why didn’t you test Donald for an STI when you tested Dina?

Going Beyond

Hundreds of clinics, websites, and institutes have been formed to deal exclusively with reproductive problems because of the many, many causes for imbalance in the human reproductive system. Research some of the other reproductive disorders, such as endometriosis, ovarian cysts, impotence, yeast infections, and Toxic Shock Syndrome. Use these terms and “human reproductive science” as Internet search terms.

Module 3: Section 1—Lesson 5 Assignment

There is no assignment for this lesson.

2.3.5S1 page 4

Lesson Summary

In Lesson 5 you investigated the following focusing questions:

• How do diseases and sexually transmitted infections compromise structural fertility?

Given the many possible problems that can occur in human reproductive systems, it is amazing that healthy babies are born every day. Humans are constantly affected by structural and hormonal problems due to STIs and other disorders, sometimes without even knowing it. Yet the species continues. There are now more than six billion human beings on the planet! Our reproductive strategy is obviously working. Or should it be said that it has been working?

Human reproduction may now be on the decline. In 1960, the world fertility rate was six children per woman. Today, the rate is three children per woman. Although there are many reasons for reduced fertility rates, estimates state that over 300 million people contract new sexually transmitted infections every year and over 5 million people become infected with HIV every year

Young Canadians in your age group have some of the highest rates of STIs in the country. STIs are not only passed between sexual partners but can also be spread from mother to child during childbirth and breastfeeding. Many STIs are lifelong infections with little to no treatment options.

While cancer is not transmitted through the sharing of body fluids, like STIs it is a disorder that affects fertility and is on the rise. The World Health Organization (WHO) states that global cancer rates could increase by 50% to 15 million by 2020. Even though these numbers are for all types of cancers, because they include reproductive cancers, it can be assumed that reproductive cancers are also on the rise. WHO further states that up to 23 percent of malignancies in developing countries are caused by infectious agents, including hepatitis B and C viruses and human papillomaviruses. These can lead to cervical cancer. Developed countries, like Canada, have a much higher cervical cancer detection rate than underdeveloped countries. As a result, women in developed countries are less likely to die from this disease. One tool used for early detection and treatment of cervical cancer is the PAP smear. Women are encouraged by their doctors to have a PAP smear every year.

To maintain your overall health, your chance to have a baby, and the safety of any future sexual partners, it is imperative that you understand the facts surrounding STIs and make good choices regarding your reproductive health.

Module Summary

Module Summary—Section 1

Throughout Section 1 you have learned about human reproduction. The information presented in the lessons has helped you assess the importance of your reproductive health. As you head into your reproductive years, it is important to learn the structures and function of the male and female reproductive systems and how each system forms functional gametes. Making choices that maintain your sexual health are vital for who you are now and your plans for a future family. By understanding how sexually transmitted diseases can affect your reproductive system and society as a whole, you are better informed to make healthy choices. Examining reproductive technologies will help you understand how infertility issues can be addressed and the ethical issues for you to consider as a member of society.

Module Assessment—Section 1

You should have completed and submitted the following assignments.

Bio30 2.3.1S1 online assignment

Bio30 2.3.2S1 online assignment

Bio30 2.3.3S1 online assignment

Bio30 2.3.5S1 online assignment