testes are the male reproductive organs, and are responsible for the manufacturing of the male sex cell, the sperm.
testes are approximately the size of two large olives, and are located in the scrotum, a sac of skin which hangs under the
penis. Sperm can only be produced in a temperature lower than that of the rest of the body, and the scrotum, which keeps the
testes separate from the body, provides these organs with the suitable conditions.
testes themselves is divided into smaller lobules, and surrounded by a white covering called the tunica albuginea. Inside
each lobule are the seminiferous tubules, which is where sperm cells are formed. Inside the seminiferous tubules, the stem
cells, called spermatogonia, undergo meiosis and develop into sperm cells. The semi- mature sperm are pushed from the testes
into the adjacent epididymis. The epididymis is a thin 20 meter tube wrapped tightly in a c-shaped membrane along the side
of the testes.
being pushed out of the seminiferous tubules of the testes, the immature sperm remain in the epididymis for approximately
twenty days, moving along the length of the tube. Here they mature fully and gain the ability to swim. The epididymis is attached
to the vas deferens, a muscular tube that connects the epididymis, and ultimately the testes to the urethra and the outside
world. The vas deferens extends upwards into the body, over the bladder, past the seminal vesicle, where semen is produced,
through the prostate and out of the shaft of the penis. During ejaculation, the muscular walls of the vas deferens contract,
pushing the sperm out of the epididymis and out through the urethra.
testes are also responsible for the production of testosterone, which is produced in the interstitial cells of the testes
which surround the seminiferous tubules. Testosterone is responsible for the development of secondary sex characteristics
of the males, like the deepening of the voice and hair growth, the maturation of the male reproductive system during puberty,
and sex drive. The interstitial cells are stimulated to produce testosterone by luteinizing hormone secreted by the pituitary
gland, and are also responsible for the final stages of development of sperm.