In this chapter... Humans can only reproduce through sexual reproduction, but we’ll explore asexual reproduction in other organisms. Human life cycles will be a major focus, including details of meiosis and fertilization. As part of development, gene regulation guides the differentiation of cells. Finally, we’ll explore the roles of sex chromosomes in determining gender and as a mode of inheritance.

The overall function of the reproductive system is pretty simple – to make babies. The goal may be simple, but the process is not. From courtship to pregnancy and childbirth, the reproductive process is probably the most complex thing that humans do, but also the most meaningful.

Why this is important…No organism lives forever. Just like cells get worn out and need to be replaced, so does each generation. This system makes the continued existence of our species (or any species) possible. Plus, who doesn’t love babies?

Foundations

This is the only organ system for which we need different diagrams for male and female. Even though male and female anatomy is very different, both start life with the same anatomy. After 6 weeks of development in the uterus, one gene can change the course of development resulting in either a baby boy or baby girl.

Details

It is an understatement to say that females face greater challenges in reproduction than males. During pregnancy, a woman’s body must tolerate a genetically foreign intruder for 9 months. Not only does her immune system tolerate the foreigner, but she must nourish it while her own body functions become more compromised.

Anatomy of female reproductive system.

FIGURE 11-1 Anatomy of the female reproductive system. ("Female genital system" by R. Dewaele (Bioscope, Unige), J. Abdulcadir (HUG), C. Brockmann (Bioscope, Unige), O. Fillod, S. Valera-Kummer (DIP), www.unige.ch/ssi is licensed under CC BY-SA 4.0)

A basic overview of the female reproductive organs.

Ovaries produce eggs (ova) as well as the hormones estrogen and progesterone.
Uterine tubes carry the egg to the uterus. (These are also called oviducts or Fallopian tubes)
Uterus is where the fetus develops. The cervix is the “neck” of the uterus, which usually remains closed, but dilates to 10 centimeters during childbirth.
Vagina is where semen is received during sex. It also serves as the birth canal for the baby.

The male’s role in reproduction is to make lots and lots of sperm. Millions of sperm are needed to maximize the chances of fertilizing an egg. Since men don’t have the ability to become pregnant, the biological role of males may be done after contributing sperm.

Anatomy of male reproductive system.

FIGURE 11-2 Anatomy of the male reproductive system. ("Male genital system" by R. Dewaele (Bioscope, Unige), J. Abdulcadir (HUG), C. Brockmann (Bioscope, Unige), O. Fillod, S. Valera-Kummer (DIP), www.unige.ch/ssi is licensed under CC BY-SA 4.0)

A basic overview of the male reproductive organs.

Testes produce sperm in a long series of coiled tubes. They also produce testosterone.
Epididymis stores mature sperm.
Vas deferens carries sperm to the urethra.
Penis delivers sperm into the vagina through the urethra.
There are also accessory glands (prostate and seminal vesicles) that produce fluids that protect and nourish the sperm. These fluids make up most of the semen.

Learning objectives

Name and identify the major organs of the male and female reproductive system
Describe the basic functions of the reproductive system