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The Testes

Table of Contents
The Lungs
The Trachea
The Testes
The Submaxillary Gland
The Liver
The Stomach and Duodenum
The Blood
The Arteries and Veins
The Adipose Tissue
The Skin
The Pituitary Gland
The Pancreas
The Thyroid
The Kidney
The Spinal Cord
The Cerebellum
The Elastic Cartilage
The Bone
The Smooth Muscle
The Striated Muscle


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The testes are the male reproductive organs, and are responsible for the manufacturing of the male sex cell, the sperm.


The 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.


The 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.


After 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.


The 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.