22: Reproductive System

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This chapter outlines the structures and functions of the male and female reproductive systems, explains how fertilization occurs, and discusses the role of the menstrual cycle in female reproduction. The chapter also describes causes of, and treatments for, male and female reproductive system disorders and infertility. In addition, it discusses types of contraception and their effectiveness.

22.1: Case Study: Making Babies
Alicia, 28, and Victor, 30, have been married for three years. A year ago, they decided they wanted to have a baby, and they stopped using birth control. At first, they did not pay attention to the timing of their sexual activity in relation to Alicia’s menstrual cycle, but after six months passed without Alicia becoming pregnant, they decided to try to maximize their efforts.
22.2: Introduction to the Reproductive System
The reproductive system is the human organ system responsible for the production and fertilization of gametes (sperm or eggs) and, in females, the carrying of a fetus. Both male and female reproductive systems have organs called gonads that produce gametes. A gamete is a haploid cell that combines with another haploid gamete during fertilization, forming a single diploid cell called a zygote. Besides producing gametes, the gonads also produce sex hormones.
22.3: Structures of the Male Reproductive System
First, they are peeled and pounded flat. Then, they are coated in flour, seasoned with salt and pepper, and deep fried. What are they? They are often called Rocky Mountain oysters, but they don’t come from the sea. They may also be known as Montana tendergroin, cowboy caviar, or swinging beef — all names that hint at their origins. Here’s another hint: they are harvested only from male animals, such as bulls or sheep. What are they? In a word: testes.
22.4: Functions of the Male Reproductive System
The false-color image in Figure 22.4.1 shows real human sperm. The tiny gametes are obviously greatly magnified in the picture, because they are actually the smallest of all human cells. In fact, human sperm cells are small, even when compared with sperm cells of other animals. Mice sperm are about twice the length of human sperm! Human sperm may be small in size, but in a normal, healthy man, huge numbers of them are usually released during each ejaculation. There may be hundreds of millions
22.5: Disorders of the Male Reproductive System
The marble penis and scrotum depicted above comes from ancient Rome, during the period from about 200 BCE to 400 CE. During that time, offerings like this were commonly given to the gods by people with health problems, either in the hopes of a cure, or as thanks for receiving one. The offerings were generally made in the shape of the afflicted body part. Scholars think this marble penis and scrotum may have been an offering given in hopes of — or thanks for — a cure for impotence, known medicall
22.6: Structures of the Female Reproductive System
The female reproductive system is made up of internal and external organs that function to produce haploid female gametes called eggs (or oocytes), secrete female sex hormones (such as estrogen), and carry and give birth to a fetus. The internal female reproductive organs include the vagina, uterus, Fallopian (uterine) tubes, and ovaries. The external organs — collectively called the vulva — include the clitoris and labia.
22.7: Functions of the Female Reproductive System
At birth, a female’s ovaries contain all the eggs she will ever produce, which may include a million or more eggs. The eggs don't start to mature, however, until she enters puberty and attains sexual maturity. After that, one egg typically matures each month, and is released from an ovary. This continues until a woman reaches menopause (cessation of monthly periods), typically by age 52. By then, viable eggs may be almost depleted, and hormone levels can no longer support the monthly cycle.
22.8: Menstrual Cycle
The menstrual cycle refers to natural changes that occur in the female reproductive system each month during the reproductive years. The cycle is necessary for the production of eggs and the preparation of the uterus for pregnancy. It involves changes in both the ovaries and the uterus, and is controlled by pituitary and ovarian hormones. Day 1 of the cycle is the first day of the menstrual period, when bleeding from the uterus begins as the built-up endometrium lining the uterus is shed.
22.9: Disorders of the Female Reproductive System
Cervical cancer is one of three disorders of the female reproductive system described in detail in this concept. Of the three, only cervical cancer can be prevented with a vaccine.
22.10: Infertility
Infertility is the inability of a sexually mature adult to reproduce by natural means and is generally defined as the failure to achieve a successful pregnancy after at least one year of regular, unprotected sexual intercourse. Primary infertility applies to cases in which an individual has never achieved a successful pregnancy. Secondary infertility applies to cases in which an individual has had at least one successful pregnancy, but fails to achieve another after trying for at least a year.
22.11: Contraception
Contraception, also known as birth control, is any method or device used to prevent pregnancy. Birth control methods have been used for centuries, but safe and effective methods only became available in the 20th century. Many different birth control methods are currently available, but they differ considerably in their effectiveness at preventing pregnancy.
22.12: Case Study Conclusion: Trying to Conceive and Chapter Summary
The woman in the photograph above is holding a home pregnancy test. The two pink lines in the middle are the type of result that Alicia and Victor are desperately hoping to see themselves one day — a positive pregnancy test. In the beginning of the chapter you learned that Alicia and Victor have been actively trying to get pregnant for a year, which, as you now know, is the time-frame necessary for infertility to be diagnosed.

Thumbnail: Movements of a human embryo of a gestational age of almost exactly 9 weeks.Häggström, Mikael (2014). "Medical gallery of Mikael Häggström 2014". WikiJournal of Medicine 1 (2).(Public Domain).