What To Know About Testicles

People with male reproductive organs usually have two testicles (testes), commonly called balls. Testicles produce sperm and testosterone, a male sex hormone. These egg-shaped organs are located in the scrotum, which is below the penis. The average testicle size is 4–5 centimeters (cm) in length, 3 cm in height, and 2.5 cm in width.

The testicles have several nerve endings, making them highly sensitive to arousal and pain. You are likely aroused if your testicles feel full and appear larger than usual. You may also experience an uncomfortable aching feeling, known as "blue balls," if you are aroused and do not orgasm.

Other conditions associated with the testicles include testicular cancer and torsion. Read to learn about the anatomy and function of testicles, when your balls are "full," as well as how to keep your testicles healthy.

Anatomy of the Testicles or Balls

Males typically have two testicles, which are paired in the scrotum. The scrotum is located below the penis in the pelvic region.

Structure

Testicles are egg-shaped and 4–5 cm lengthwise, 3 cm heightwise, and 2.5 cm widthwise. Tunica, a double-layered fibrous tissue, surrounds each testis.

The testicles are made up of lobules, which contain seminiferous tubules. These narrow tubes produce and carry sperm to the rete testis, a conduit that helps transfer sperm to the epididymis, which stores it.

Testicular temperature must be about 5 degrees lower than the rest of your body to properly create and preserve sperm. The scrotum is about 93.4 degrees, while the body is typically 98.6 degrees. The scrotal muscles help control the temperature of your testicles. These muscles move the testicles closer to or farther away from your body as the air gets warmer or cooler.

The left testicle usually hangs a little lower than the right one, which allows your body to change one testis's temperature without affecting the other. It's also normal to have one slightly bigger testicle. The right tends to be larger than the left.

The testicles are vulnerable because they hang outside of your body. Each testis has several nerve endings that are highly sensitive to pain. The scrotal muscles will pull the testes closer to your body if they sense danger, even if it's not actual danger. All those nerve endings can also lead to pleasure. The scrotal sack around the testes is considered an erogenous zone.

Location

The testicles are located in the scrotum, which is a wrinkled pouch of skin that hangs below the penis. The spermatic cord suspends each testis from the abdomen.

Anatomical Variations

There are several anatomical variations in the testicles, which can be congenital (present at birth) or develop from injury or trauma to the area. Anatomical variations include:

• Appendix testis: This excess tissue on the testicles is usually harmless but might twist, causing pain.
• Bell clapper deformity: This causes the testes to hang freely in the scrotum, which increases your risk of testicular torsion (twisting).
• Monorchism: This is the presence of one testis in the scrotum. Monorchism may be present at birth or result from testicular torsion, trauma, or surgery.
• Polyorchidism: This rare variation results in more than two testicles in the scrotum.
• Undescended testicles: The testicles typically drop from the abdomen to the scrotum during fetal development. A baby is sometimes born with undescended testicles, or one or both testicles still in the abdomen. Undescended testicles may drop on their own, but surgery is usually needed if they have not dropped within six months.

What Do the Testicles Do?

The testicles or "balls" produce about 1,000 sperm per second. That's about 60,000 sperm per minute, 3.6 million per hour, and 86.4 million per day. The testicles constantly create sperm through a process called spermatogenesis. This means your balls are continually "full" of sperm, and pregnancy can occur with vaginal intercourse even if you have recently ejaculated. An increase in follicle-stimulating hormone (FSH) triggers this process.

Each person is different, and sperm count can vary. The average ejaculation typically contains anywhere from 20–150 million sperm per milliliter. It only takes one sperm to fertilize an egg, but having plenty of sperm increases the chances of conception.

Your testes also produce the hormone testosterone, which your body needs to make sperm. This sex hormone is responsible for muscle development, body hair growth, and deepening of the voice. The anterior pituitary gland in your brain secretes luteinizing hormone (LH) to control testosterone production.

Associated Conditions

Several health conditions may affect the testicles, which may cause inflammation, pain, and swelling of the testes and scrotum. Some of these conditions are benign (non-cancerous) and go away on their own, while others require medical attention.

Epididymal Hypertension (Blue Balls)

The medical name for "blue balls," or an aching feeling if you have an erection but do not orgasm, is epididymal hypertension (EH). The blood vessels to the penis and testicles expand to make room for increased blood flow, causing the penis to become erect. This increased blood flow subsides after an orgasm.

Your testicles do not actually turn blue, despite the name. You may develop mild discomfort if you do not have an orgasm. Blue balls are not dangerous, and you do not have to have partnered sex to relieve the symptoms. Waiting it out or masturbating can make the discomfort go away. 

Epididymitis

Epididymitis is swelling of the epididymis, which stores sperm in the testicles. A bacterial infection in the bladder, prostate, or urethra usually causes epididymitis. The prostate is a gland that creates fluid to carry semen out of the urethra. Other causes include chlamydia and gonorrhea, which are sexually transmitted infections (STIs).

Symptoms include:

• Blood in the semen
  
• Discharge from the urethra
• Fever and chills
• A heavy feeling in the testicles
• A lump near the testicles
• Pain during ejaculation or when urinating
• Pain, swelling, and tenderness near the groin
• Testicle pain that worsens during bowel movements

Hypogonadism

Hypogonadism is an endocrine (hormone) disorder that causes the gonads to make little to no hormones. The gonads are the testes in males, and the affected hormone is testosterone. Common causes of hypogonadism include autoimmune and genetic disorders, infection, trauma, and surgery.

Hypogonadism may cause symptoms like:

• Breast enlargement
• Growth problems, which affect body hair growth and deepening of the voice
• Low libido
• Muscle loss

Orchitis

Orchitis is swelling of the testicles, usually caused by a bacterial or viral infection. Mumps, a viral infection that affects the salivary glands, typically causes orchitis in young children.

Symptoms include:

• Blood in the semen
• Discharge from the urethra
• Fever
• Groin and testicle pain
• A heavy feeling in the testicles
• Pain, swelling, and tenderness near the groin
• Painful intercourse and ejaculation

Testicular Cancer

Testicular cancer is the most common cancer in men aged 20–35. People often catch testicular tumors late because they do not notice symptoms. Testicular tumors can grow without compressing nearby bones and organs, making them relatively painless. The skin of the scrotum is also so loose a testicular tumor can grow without constraint. 

Symptoms include:

• Aching or pain in your abdomen, back, groin, or scrotum
• Changes in the size of one or both testes
• A heavy feeling in the scrotum
• A lump on the testicles
  

Testicular Torsion

Testicular torsion happens if the testes twist and rotate the spermatic cord, which moves blood to your testicles. This twisting cuts off blood flow to the affected testis, resulting in pain and tissue death. Testicular torsion is rare and is more common in people under 25.

Testicular torsion is an emergency. Get medical attention right away if you have symptoms like:

• A hard and high-riding teste
• Nausea and vomiting
• Severe scrotal pain
• Swelling of the scrotum

Your risk of losing the testis increases if a surgeon does not untwist it within eight hours of symptom onset. Other complications include infection, infertility, and testicular atrophy.

Varicocele

Varicocele is swelling of the veins along the spermatic cord in the scrotum, which occurs if something prevents blood flow.

Symptoms include:

• Discomfort
• Enlarged veins in the scrotum that twist
• Fertility problems, including low sperm count
• A lump near the testicles that's painless
• Swelling of the scrotum

Diagnostic Testing

A healthcare provider might perform diagnostic tests if you develop symptoms that affect the testicles. Common diagnostic tests include:

• Magnetic resonance imaging (MRI): A healthcare provider might use this imaging test, which uses magnets and radio waves, to take detailed pictures of the inside of your scrotum. You might require an MRI if you detect a lump near the testicles.
• Physical exam: A healthcare provider will feel each testis at a time, rolling it gently between their thumb and fingers. They will check to see if the testis is enlarged or hardened. They may feel around your abdominal and pelvic areas for other abnormalities.
• Ultrasound: This imaging test uses sound waves to look at the scrotum and check for health concerns, such as testicular cancer or torsion.

Tips for Keeping Your Testicles Healthy

Here are some ways to make sure your testicles are healthy:

• Avoid hot temperatures for long periods: Anything that turns up the heat, like regularly sitting in a hot tub for a long time, may decrease sperm count and quality.
• Check your testicles regularly: Testicular cancer is highly curable, but self-exams are important. Examine one testis at a time after you jump out of the shower when the scrotum's skin is relaxed. Use both hands to gently roll one testis between your thumb and fingers. The testicles are normally symmetrical and round. Talk to a healthcare provider if you notice hard lumps or bumps or changes in the size or shape of your testicles.
• Keep your genitals clean: Make sure you bathe or shower regularly to prevent infections that might affect the testes.
• Wear loose-fitting underwear: This gives your testicles enough space to regulate temperature. Research has found people with testes who primarily wear boxer shorts average 25% higher sperm concentration and 17% higher total sperm count than those who wear other types of underwear like briefs or jockeys.

A Quick Review

Testicles, sometimes called "balls," are male reproductive organs located in the scrotum. They create sperm and testosterone and are highly sensitive to arousal and pain. People typically have two testicles.

You may develop inflammation, pain, and swelling of the testes and scrotum, which might indicate a health problem. A healthcare provider can administer tests to diagnose the underlying cause. Tips for keeping testicles healthy include avoiding hot temperatures for long periods, performing self-exams, and wearing loose-fitting underwear.