Which of the following lists the correct order of the male reproductive ducts sperm passes through on its way from the testes to the urethra?

The male reproductive system includes the penis, scrotum, testes, epididymis, vas deferens, prostate, and seminal vesicles.

The penis consists of the root (which is attached to the lower abdominal structures and pelvic bones), the visible part of the shaft, and the glans penis (the cone-shaped end). The opening of the urethra (the channel that transports semen and urine) is located at the tip of the glans penis. The base of the glans penis is called the corona. In uncircumcised males, the foreskin (prepuce) extends from the corona to cover the glans penis.

The penis includes three cylindrical spaces (blood-filled sinuses) of erectile tissue. The two larger ones, the corpora cavernosa, lie side by side. The third sinus, the corpus spongiosum, surrounds most of the urethra. When these spaces fill with blood, the penis becomes large and rigid (erect).

The scrotum is the thick-skinned sac that surrounds and protects the testes. The scrotum also acts as a climate-control system for the testes because they need to be slightly cooler than body temperature for normal sperm development. The cremaster muscles in the wall of the scrotum relax to allow the testes to hang farther from the body to cool or contract to pull the testes closer to the body for warmth or protection.

The testes are oval bodies that average about 1.5 to 3 inches (4 to 7 centimeters) in length and 2 to 3 teaspoons (20 to 25 milliliters) in volume. Usually the left testis hangs slightly lower than the right one. The testes have two primary functions:

• Producing sperm (which carry the man's genes)

• Producing testosterone (the primary male sex hormone)

The epididymis consists of a single coiled microscopic tube that measures almost 20 feet (6 meters) in length. The epididymis collects sperm from the testis and provides the environment for sperm to mature and acquire the ability to move through the female reproductive system and fertilize an ovum. One epididymis lies against each testis.

The vas deferens is a firm tube (the size of a strand of spaghetti) that transports sperm from the epididymis. One such duct travels from each epididymis to the back of the prostate and joins with one of the two seminal vesicles. In the scrotum, other structures, such as muscle fibers, blood vessels, and nerves, also travel along with each vas deferens and together form an intertwined structure, the spermatic cord.

The urethra serves a dual function in males. This channel is the part of the urinary tract that transports urine from the bladder and the part of the reproductive system through which semen is ejaculated.

The seminal vesicles, located above the prostate, join with the vas deferens to form the ejaculatory ducts, which travel through the prostate. The prostate and the seminal vesicles produce fluid that nourishes the sperm. This fluid provides most of the volume of semen, the fluid in which the sperm is expelled during ejaculation. Other fluid that makes up a very small amount of the semen comes from the vas deferens and from Cowper glands in the urethra.

Reproduction is the process by which organisms make more organisms like themselves. But even though the reproductive system is essential to keeping a species alive, unlike other body systems, it's not essential to keeping an individual alive.

In the human reproductive process, two kinds of sex cells, or gametes (pronounced: GAH-meetz), are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female's reproductive system. When sperm fertilizes (meets) an egg, this fertilized egg is called a zygote (pronounced: ZYE-goat). The zygote goes through a process of becoming an embryo and developing into a fetus.

The male reproductive system and the female reproductive system both are needed for reproduction.

Humans, like other organisms, pass some characteristics of themselves to the next generation. We do this through our genes, the special carriers of human traits. The genes that parents pass along are what make their children similar to others in their family, but also what make each child unique. These genes come from the male's sperm and the female's egg.

What Is the Male Reproductive System?

The male has reproductive organs, or genitals, that are both inside and outside the pelvis. The male genitals include:

• the testicles (pronounced: TESS-tih-kulz)
• the duct system, which is made up of the epididymis and the vas deferens
• the accessory glands, which include the seminal vesicles and prostate gland
• the penis

In a guy who has reached sexual maturity, the two oval-shaped testicles, or testes (pronounced: TESS-teez) make and store millions of tiny sperm cells.

The testicles are also part of the endocrine system because they make hormones, including testosterone (pronounced: tess-TOSS-tuh-rone). Testosterone is a major part of puberty in guys. As a guy makes his way through puberty, his testicles produce more and more of it. Testosterone is the hormone that causes boys to develop deeper voices, bigger muscles, and body and facial hair. It also stimulates the production of sperm.

Alongside the testicles are the epididymis and the vas deferens, which transport sperm. The epididymis (pronounced: ep-uh-DID-uh-miss) and the testicles hang in a pouch-like structure outside the pelvis called the scrotum. This bag of skin helps to regulate the temperature of testicles, which need to be kept cooler than body temperature to produce sperm. The scrotum changes size to maintain the right temperature. When the body is cold, the scrotum shrinks and becomes tighter to hold in body heat. When it's warm, it gets larger and floppier to get rid of extra heat. This happens without a guy ever having to think about it. The brain and the nervous system give the scrotum the cue to change size.

The accessory glands, including the seminal vesicles and the prostate gland, provide fluids that lubricate the duct system and nourish the sperm. The urethra (pronounced: yoo-REE-thruh) is the channel that carries the sperm (in fluid called semen) to the outside of the body through the penis. The urethra is also part of the urinary system because it is also the channel through which pee passes as it leaves the bladder and exits the body.

The penis is actually made up of two parts: the shaft and the glans. The shaft is the main part of the penis and the glans is the tip (sometimes called the head). At the end of the glans is a small slit or opening, which is where semen and pee exit the body through the urethra. The inside of the penis is made of a spongy tissue that can expand and contract.

Like other living things, human beings reproduce. It's what keeps the population going. 

The male and female reproductive systems work together to make a baby. Click through this slideshow to see how the male reproductive system works.

The penis is made of two parts: the shaft (the main part) and the glans (the tip, sometimes called the head). The scrotum is a pouch-like structure that keeps the testicles at the right temperature.

The two testicles (or testes) produce sperm and the male sex hormone testosterone.

Next to each testicle, the epididymis is a tube where sperm is stored. From here, sperm are transported to the vas deferens.

Also called the ductus deferens, the vas deferens is a thin muscular tube that transports the sperm from the epididymis to the urethra.

The prostate gland is a walnut-sized gland that surrounds a portion of the urethra and produces some of the fluid in semen.

Located at the base of the bladder, the two seminal vesicles secrete a thick fluid that nourishes the sperm.

The bladder is the muscular sac that stores urine (pee) until it is released through the urethra.

The urethra is the tube that carries semen and urine out of the penis.

When the sperm and an egg meet in the female's reproductive system, the sperm fertilizes the egg, forming a zygote. The zygote becomes an embryo and then develops into a fetus.

After about 40 weeks, a baby is born.

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All boys are born with a foreskin, a fold of skin at the end of the penis covering the glans. Some boys are circumcised, which means that a doctor or clergy member cuts away the foreskin. Circumcision is usually done during a baby boy's first few days of life. It's not medically necessary, but parents who choose to have their sons circumcised often do so based on religious beliefs, concerns about hygiene, or cultural or social reasons. Guys who have circumcised penises and those who don't are no different: All penises work and feel the same, regardless of whether the foreskin has been removed.

How Does the Male Reproductive System Work?

The male reproductive system:

• makes semen (pronounced: SEE-mun)
• releases semen into the reproductive system of the female during sexual intercourse
• produces sex hormones, which help a boy develop into a sexually mature man during puberty

When a baby boy is born, he has all the parts of his reproductive system in place, but it isn't until puberty that he is able to reproduce. When puberty begins, usually between the ages of 9 and 15, the — located near the brain — secretes hormones that stimulate the testicles to produce testosterone. The production of testosterone brings about many physical changes.

Although the timing of these changes is different for every guy, the stages of puberty generally follow a set sequence:

• During the first stage of male puberty, the scrotum and testes grow larger.
• Next, the penis becomes longer and the seminal vesicles and prostate gland grow.
• Hair begins to grow in the pubic area and later on the face and underarms. During this time, the voice also deepens.
• Guys also have a growth spurt during puberty as they reach their adult height and weight.

What Do Sperm Do?

A male who has reached puberty will produce millions of sperm cells every day. Each sperm is extremely small: only 1/600 of an inch (0.05 millimeters long). Sperm develop in the testicles within a system of tiny tubes called the seminiferous tubules. At birth, these tubules contain simple round cells. During puberty, testosterone and other hormones cause these cells to transform into sperm cells. The cells divide and change until they have a head and short tail, like tadpoles. The head contains genetic material (genes). The sperm move into the epididymis, where they complete their development.

The sperm then move to the vas deferens (pronounced: VAS DEF-uh-runz), or sperm duct. The seminal vesicles and prostate gland make a whitish fluid called seminal fluid, which mixes with sperm to form semen when a male is sexually stimulated. The penis, which usually hangs limp, becomes hard when a male is sexually excited. Tissues in the penis fill with blood and it becomes stiff and erect (an erection). The rigidity of the erect penis makes it easier to insert into the female's vagina during sex. When the erect penis is stimulated, muscles around the reproductive organs contract and force the semen through the duct system and urethra. Semen is pushed out of the male's body through his urethra — this process is called ejaculation. Each time a guy ejaculates, it can contain up to 500 million sperm.

What Is Conception?

If semen is ejaculated into a female's vagina, millions of sperm "swim" up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. It takes only one sperm to fertilize the egg.

This fertilized egg is now called a zygote and contains 46 chromosomes — half from the egg and half from the sperm. Genetic material from the male and female combine so that a new individual can be created. The zygote divides again and again as it grows in the female's uterus, maturing over the course of the pregnancy into an embryo, a fetus, and finally a newborn baby.