The testicles, also known as testes, are the primary male reproductive glands in humans and other mammals. These oval-shaped organs are housed within the scrotum. They play a dual role in the male body, functioning as part of both the reproductive and endocrine (hormone) systems. Their location and internal structure support these roles, contributing to male health and fertility.
Anatomy and External Location
Each testicle, an oval structure, measures approximately 4 to 5 centimeters in length and about 2 to 3 centimeters in diameter, weighing around 25 grams. They are covered by a tough, fibrous capsule, the tunica albuginea, which extends inward to divide the organ into 200 to 400 wedge-shaped sections called lobules. Within each lobule are highly coiled tubes, the seminiferous tubules, which are the sites of sperm development.
Sperm cells, once produced, travel from the seminiferous tubules to the epididymis, a long, coiled tube resting on the back of each testicle. Here, immature sperm mature and are stored until ready for ejaculation. The testicles are housed within the scrotum, which hangs outside the abdominal cavity. This external placement is important because sperm production, or spermatogenesis, requires a temperature slightly lower than core body temperature, about 2 to 3 degrees Celsius cooler. The scrotum has specialized muscles that contract or relax to move the testicles closer to or further from the body, regulating temperature for optimal sperm viability.
The Dual Functions of the Testicles
The testicles perform two distinct functions: producing sperm and producing hormones. Spermatogenesis is the continuous process of sperm creation, beginning at puberty and continuing throughout a male’s life. This process occurs within the seminiferous tubules, where precursor cells called spermatogonia undergo divisions and transformations, taking 42 to 76 days to fully mature.
In addition to sperm production, the testicles are the primary site for male hormone synthesis, particularly testosterone. Specialized Leydig cells, located between the seminiferous tubules, produce this androgen. Testosterone is responsible for the development of male secondary sexual characteristics, such as increased muscle mass and bone density, a deeper voice, and the growth of facial and body hair. It also influences libido, red blood cell production, and overall mood and energy levels.
Common Medical Conditions and Injuries
Several medical conditions and injuries can affect the testicles. Testicular torsion is an emergency that occurs when the spermatic cord, which supplies blood to the testicle, twists, cutting off blood flow. This condition causes sudden, severe pain in the scrotum, often accompanied by swelling, nausea, and vomiting, and requires immediate medical attention to prevent permanent damage.
Testicular cancer, though relatively uncommon, is the most frequently diagnosed cancer in men aged 15 to 35. The most common symptom is a painless lump or swelling in one testicle, though some individuals may experience discomfort or a feeling of heaviness. Early detection significantly improves treatment outcomes.
Epididymitis is an inflammation of the epididymis, causing pain and swelling in the back of the testicle. It is often caused by bacterial infections, including sexually transmitted infections, or by other bacterial or viral agents.
A varicocele is an enlargement of the veins within the scrotum, similar to varicose veins found in the legs. It appears as a soft lump above the testicle, often described as feeling like a “bag of worms,” and is more common on the left side. While many varicoceles cause no symptoms, they can sometimes lead to a dull ache or discomfort, and in some cases, may be associated with infertility due to impaired temperature regulation and blood flow affecting sperm production.
Testicles are vulnerable to trauma due to their external location. Injuries from direct blows, sports accidents, or falls can cause intense pain, swelling, and bruising. Severe injuries, such as rupture, require prompt medical evaluation to prevent long-term complications including infertility.
Testicular Health and Self-Examination
Maintaining testicular health involves regular self-awareness and timely medical consultation for any changes. Performing a testicular self-examination (TSE) monthly is an effective way to become familiar with the normal feel of your testicles, making it easier to notice abnormalities. The best time to perform a TSE is during or immediately after a warm shower or bath, as the warmth relaxes the scrotal skin, allowing for easier examination.
During the self-exam, gently roll each testicle between your thumb and fingers, feeling for any new lumps, swelling, or changes in size or shape. It is common for one testicle to be slightly larger or hang lower than the other, and a soft, cord-like structure called the epididymis can be felt at the back of each testicle. Any new lump, persistent pain, unexplained swelling, or significant changes in the size or shape of a testicle should prompt a visit to a healthcare provider for professional evaluation.