Testicle
Male gonad producing sperm and androgens, regulated by pituitary hormones.
A testicle, also called testis (pl. testes), is the male gonad in all gonochoric animals, including humans, and is homologous to the ovary, the female gonad. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The release of testosterone is regulated by luteinizing hormone (LH) from the anterior pituitary gland, while sperm production is controlled by follicle-stimulating hormone (FSH) and testosterone.
- field
- Anatomy, Reproductive Biology
- known_for
- Male gonad producing sperm and testosterone
- average_volume
- 18 cm³ per testis (range 12–30 cm³)
- normal_volume_range
- 15 to 25 cm³
- optimal_temperature
- 34.4 °C
Lore & Background
Male humans have two testicles of similar size contained within the scrotum, an extension of the abdominal wall. Scrotal asymmetry is common; for 85% of men, the right testis hangs lower than the left due to differences in vasculature anatomy. An average adult testicle measures up to 5 cm × 2 cm × 3 cm. Testicular volume can be estimated by palpation using an orchidometer or by measuring length, width, and depth with calipers or ultrasound, then calculating volume using the ellipsoid formula. The Tanner scale assigns maturity stages from stage I (volume less than 1.5 cm³) to stage V (volume greater than 20 cm³).
Reader's Guide
The testicle is central to male reproduction and endocrinology. Its internal structure includes seminiferous tubules lined with germ cells that develop into spermatozoa through spermatogenesis, supported by Sertoli cells. Leydig cells between the tubules produce testosterone, which controls testicular volume and secondary sexual characteristics. The blood–testis barrier, formed by tight junctions between Sertoli cells, prevents auto-immune reactions against sperm antigens. Temperature regulation is critical: the scrotum and cremasteric muscle adjust testicle position to maintain 34.4 °C, as temperatures above 36.7 °C impede spermatogenesis. Testicular volume correlates positively with sperm production, making it a key factor in fertility assessment.
Did You Know?
- For 85% of men, the right testis hangs lower than the left.
- The Tanner scale assigns maturity stages from less than 1.5 cm³ (stage I) to greater than 20 cm³ (stage V).
- The blood–testis barrier prevents an auto-immune reaction against sperm antigens.
- Testicular volume is positively correlated with semen profiles and sperm count.
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