Testiklene

Testiklene are the paired gonads of many male vertebrates, including humans, where the term is used in some languages as the plural form of the organ commonly called the testicle or testis. They produce sperm and secrete androgens, primarily testosterone, which drive male development and physiology. In humans, the testes are typically located in the scrotum, separate from the abdominal cavity, allowing temperature regulation essential for sperm production.

Each testis contains seminiferous tubules where spermatogenesis occurs; interstitial cells of Leydig produce testosterone; the tunica vaginalis surrounds the organ; the testes receive blood through the testicular artery and are drained by the pampiniform plexus.

Development and function: During embryonic development, primordial germ cells migrate to the gonads; in XY individuals the testes differentiate and begin producing testosterone. At puberty, spermatogenesis becomes ongoing and sperm quality improves; testosterone regulates secondary sexual characteristics and metabolic effects.

Clinical significance: Common conditions include testicular torsion (twisting that cuts blood supply), germ cell tumors (seminomas and non-seminomas), varicocele, hydrocele, and trauma. Diagnosis relies on physical examination, ultrasound, and, for tumors, markers such as AFP, hCG, and LDH. Regular self-examination is advised.

Evolution and variation: In most mammals the testes descend into the scrotum and rely on external cooling. Some species lack a scrotum or have different temperatures; in humans, temperature affects spermatogenesis and fertility.