testis

one of the pair of male sex organs that are situated within the SCROTUM and produce SPERM and secrete the hormone TESTOSTERONE . The testicles develop within the ABDOMEN of the FOETUS but descend around the time of birth into the SCROTUM . Each testicle has an outer double MEMBRANE layer, known as the tunica vaginalis. The tunica vaginalis contains an inner fibrous layer, called the tunica albuginea, which protects the testicle. The bulk of the testicle consists of numerous fine, convoluted tubules called seminiferous tubules, which are lined with cells that produce the sperm. In addition, other cells, known as sertoli cells, occur, which provide support and possibly nourishment for the developing sperm. The tubules are supported by CONNECTIVE TISSUE containing NERVES and BLOOD VESSELS and also the cells of Leydig, which are responsible for HORMONE production. The tubules connect with another highly folded tube, called the epididymis, which is about 7 m long and connects with the VAS DEFERENS ,which leads to the URETHRA . The spermatozoa are passed by passive movement along the epididymis, completing their development as they go, and are stored in the lower part until EJACULATION .