The testes — also called testicles — are two oval-shaped organs in the male reproductive system. They’re contained in a sac of skin called the scrotum. The scrotum hangs outside the body in the front of the pelvic region near the upper thighs.

Structures within the testes are important for the production and storage of sperm until they’re mature enough for ejaculation. The testes also produce a hormone called testosterone. This hormone is responsible for sex drive, fertility, and the development of muscle and bone mass.

The main function of the testes is producing and storing sperm. They’re also crucial for creating testosterone and other male hormones called androgens.

Testes get their ovular shape from tissues known as lobules. Lobules are made up of coiled tubes surrounded by dense connective tissues.

Seminiferous tubules

Seminiferous tubules are coiled tubes that make up most of each testis. The cells and tissues in the tubules are responsible for spermatogenesis, which is the process of creating sperm.

These tubules are lined with a layer of tissue called the epithelium. This layer is made up of Sertoli cells that aid in the production of hormones that generate sperm. Among the Sertoli cells are spermatogenic cells that divide and become spermatozoa, or sperm cells.

The tissues next to the tubules are called Leydig cells. These cells produce male hormones, such as testosterone and other androgens.

Rete testis

After sperm is created in the seminiferous tubules, sperm cells travel toward the epididymis through the rete testis. The rete testis helps to mix sperm cells around in the fluid secreted by Sertoli cells. The body reabsorbs this fluid as sperm cells travel from the seminiferous tubules to the epididymis.

Before sperm can get to the epididymis, they can’t move. Millions of tiny projections in the rete testis, known as microvilli, help move sperm along to the efferent tubules.

Efferent ducts

The efferent ducts are a series of tubes that join the rete testis to the epididymis. The epididymis stores sperm cells until they’re mature and ready for ejaculation.

These ducts are lined with hair-like projections called cilia. Along with a layer of smooth muscle, cilia help move the sperm into the epididymis.

The efferent ducts also absorb most of the fluid that helps to move sperm cells. This results in a higher concentration of sperm in ejaculate fluid.

Tunica: Vasculosa, albuginea, and vaginalis

The testes are surrounded by several layers of tissue. They are the:

  • tunica vasculosa
  • tunica albuginea
  • tunica vaginalis

Tunica vasculosa is the first thin layer of blood vessels. This layer shields the tubular interior of each testicle from further layers of tissue around the outer testicle.

The next layer is called the tunica albuginea. It’s a thick, protective layer made of densely packed fibers that further protect the testes.

The outermost layers of tissue are called the tunica vaginalis. The tunica vaginalis consists of three layers:

  • Visceral layer. This layer surrounds the tunica albuginea that shields the seminiferous tubules.
  • Cavum vaginale. This layer is an empty space between the visceral layer and the outermost layer of the tunica vaginalis.
  • Parietal layer. This layer is the outermost protective layer that surrounds almost the entire testicular structure.

Explore the interactive 3-D diagram below to learn more about the testes.

Many conditions can affect the testes. Here’s a list of some of the most common ones.

Hydrocele

A hydrocele happens when excess fluid builds up in the cavities around one of your testicles. This is sometimes present at birth, but it can also result from an injury or inflammation.

Hydrocele symptoms include:

  • testicular swelling that gets more noticeable as the day goes on
  • a dull ache in your scrotum
  • feeling heaviness in your scrotum

Hydroceles usually don’t require treatment unless they’re very large or painful. Most go away on their own, but more severe cases might require surgical removal.

Testicular torsion

Testicular torsion means that your testicle has rotated in the scrotum. This can wind up the spermatic cord, cutting off blood supply, nerve function, and sperm transport to your scrotum.

Symptoms of testicular torsion include:

  • severe scrotum pain
  • swelling of the testicle
  • lower abdominal pain
  • feeling nauseous
  • vomiting
  • feeling like the testicle is out of place
  • urinating more than usual

Several things can cause testicular torsion, including:

  • injury to the scrotum
  • exercising too long or hard
  • being exposed to cold temperatures
  • free movement of the testicle in the scrotum caused by a genetic condition

Your doctor can treat testicular torsion by moving the testicle by hand. Some cases might require surgery to untwist the spermatic cord.

Orchitis

Orchitis refers to a swollen or inflamed testicle. Like epididymitis, orchitis often results from an infection caused by an STI.

Orchitis symptoms include:

  • testicular pain and tenderness
  • a swollen testicle
  • fever
  • feeling nauseous
  • vomiting

Both bacterial and viral infections can cause orchitis. A combination of antibiotics or antiviral medication, along with nonsteroidal anti-inflammatory drugs or cold packs can help reduce discomfort and pain. Orchitis usually disappears in 7-10 days.

Hypogonadism

Hypogonadism happens when your body doesn’t make enough testosterone. It can result from a testicular issue or because your brain doesn’t properly stimulate hormone production.

You can be born with this condition. It can also happen due to an injury, infection, or other condition that affects testosterone production.

Symptoms of hypogonadism vary depending on age:

  • In infants. The genitals might not be clearly male, or both sets of genitals might be present.
  • In teenagers. Symptoms may include:
    • a lack of muscle development
    • little body hair growth
    • no voice deepening
    • unusual arm and leg growth relative to the rest of the body
  • In adults. Symptoms may include:
    • a lack of fertility
    • loss of body hair
    • growth of breast tissue
    • loss of bone density
    • an inability to get an erection

Hypogonadism is usually treated with hormone replacement therapy. It’s aimed at either the brain or testes, depending on the source of low testosterone production.

Testicular cancer

Testicular cancer happens when cancerous cells multiply within the tissue of your testicles. It commonly starts in the tubular testicle structures that help produce sperm.

The cause of testicular cancer isn’t always clear.

Symptoms of testicular cancer can include:

  • a lump in your testicle
  • feeling heaviness in your scrotum
  • fluids in your scrotum
  • testicular pain
  • abdominal or back pain
  • swollen or tender breast tissue

Sometimes, your doctor can surgically remove the affected tissue. In other cases, you may need to have an entire testicle removed. Radiation therapy or chemotherapy can also help destroy cancer cells.

See your doctor if you notice any of the following symptoms in one or both of your testes:

  • long-term pain that’s either dull or sharp
  • swelling
  • tenderness
  • a sensation of heaviness

Other symptoms of a problem with the testes include:

  • feeling sick
  • throwing up
  • abnormal abdominal or back pain
  • having to pee frequently
  • abnormal growth of breast tissue

Try the following to keep your scrotum in good health:

Do a monthly testicular self-exam

Roll each testicle around in your scrotum using your fingers. Check for lumps and swollen or tender areas.

Bathe regularly

Take a shower or bath every day to keep your entire genital area clean. This reduces your risk of infections that can cause other complications. Keep your penis and scrotal area dry after bathing. Moisture trapped in the area can quickly become a breeding ground for bacteria.

Wear loose, comfortable clothing

Try to avoid wearing tight underwear and pants. Allow your scrotum to hang naturally from your body to help keep the scrotal temperature low and prevent injury.

Wear protection when you have sex

Wear a condom when doing any kind of sexual activity involving your penis. This helps to prevent sexually transmitted diseases that affect your scrotum and testicles.