The testicle (from Latin testiculus, diminutive of testis, meaning “witness” of virility) is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system. The respective functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone.
In mammals, the testes are often contained within an extension of the abdomen called the scrotum. In mammals with external testes it is most common for one testicle to hang lower than the other. While the size of the testicle varies, it is estimated that 21.9% of men have their higher testicle being their left, while 27.3% of men have reported to have equally positioned testicles. This is due to differences in the vascular anatomical structure on the right and left sides.
In healthy European adult human males, average testicular volume is 18 cm³ per testis, with normal size ranging from 12 cm³ to 30 cm³. The average testicle size after puberty measures up to around 2 inches long, 0.8 inches in breadth, and 1.2 inches in height (5 x 2 x 3 cm).