Testicles

Testicles (also called testes) are two reproductive organs found in males and most male mammals with two sexes. They perform two major functions: the production of reproductive cells (sperm) and the secretion of hormones, particularly testosterone.

The testicles are contained in a loose, wrinkled pouch of skin called the scrotum, which hangs outside the lower abdomen. They are positioned externally because sperm production requires a temperature slightly lower than normal body temperature.

Structure

Each testicle is roughly oval or egg-shaped and surrounded by a tough fibrous layer. Inside are coiled tubules (seminiferous tubules) where sperm is produced. Between these tubules are specialized cells that produce the hormone testosterone. Sperm leaving the tubules passes into a long coiled tube (epididymis) attached to the testicle, where it matures and is stored.

Function

The first function is sperm production, which occurs continuously from puberty onward. The second is hormone production: testosterone drives male characteristics such as voice deepening, body hair, muscle growth and bone strength, and also supports sexual function. These functions are regulated by structures in the brain (the hypothalamus and pituitary gland) that send hormones to the testicles.

Development

During fetal development, the testicles form inside the abdomen and then descend to the scrotum, usually before birth or in the first weeks of life. If descent fails, a condition called cryptorchidism (undescended testis) may require medical treatment.

Medical conditions

Common conditions include inflammation or infection of the testicle (orchitis), fluid accumulation (hydrocele), enlargement of blood vessels (varicocele), and testicular torsion, which is sudden and requires urgent treatment. Testicular cancer also occurs, most often in younger to middle-aged men, and when detected early responds well to treatment. Certain illnesses or medications can affect fertility.