How do testicles work

The male genitals include:. In a guy who has reached sexual maturity , the two oval-shaped testicles , or testes TESS-teez make and store millions of tiny sperm cells.

The testicles are also part of the endocrine system because they make hormones , including testosterone tess-TOSS-tuh-rone. Testosterone is a major part of puberty in boys, and as a guy makes his way through puberty, his testicles produce more and more of it. Testosterone is the hormone that causes boys to develop deeper voices , bigger muscles, and body and facial hair. It also stimulates the production of sperm.

Alongside the testicles are the epididymis and the vas deferens, which transport sperm. The epididymis ep-uh-DID-uh-miss and the testicles hang in a pouch-like structure outside the pelvis called the scrotum. This bag of skin helps to regulate the temperature of testicles, which need to be kept cooler than body temperature to produce sperm.

The scrotum changes size to maintain the right temperature. When the body is cold, the scrotum shrinks and becomes tighter to hold in body heat. When it's warm, it gets larger and floppier to get rid of extra heat. This happens without a guy ever having to think about it. The brain and the nervous system give the scrotum the cue to change size. The accessory glands , including the seminal vesicles and the prostate gland , provide fluids that lubricate the duct system and nourish the sperm.

The urethra is the channel that carries the sperm in fluid called semen to the outside of the body through the penis. The urethra is also part of the urinary system because it is also the channel through which pee passes as it leaves the bladder and exits the body.

The penis is actually made up of two parts: the shaft and the glans. The shaft is the main part of the penis and the glans is the tip sometimes called the head. At the end of the glans is a small slit or opening, which is where semen and urine exit the body through the urethra yoo-REE-thruh. The inside of the penis is made of a spongy tissue that can expand and contract. All boys are born with a foreskin , a fold of skin at the end of the penis covering the glans. Some boys are circumcised, which means that a doctor or clergy member cuts away the foreskin.

Circumcision is usually done during a baby boy's first few days of life. Sperm are produced in the seminiferous tubules of the testes. There are about of these tubes in each testis, each is the length of an arm and the width of a few hairs; the whole collection of tubules is longer than a football pitch!

Once the sperm are produced in the seminiferous tubules they pass into the epididymis, a long coiled tube in which sperm mature as they are conveyed along it. They are then ready to be released at ejaculation via the vas deferens.

The main hormone secreted by the testes is testosterone, an androgenic hormone. Testosterone is secreted by cells that lie between the seminiferous tubules, known as the Leydig cells. Testosterone is important in the first stages of developing the male reproductive organs in a foetus. It also causes the development of male characteristics such as growth of facial hair, deepening of the voice and the growth spurt that takes place during puberty. From puberty onwards, testosterone provides the main stimulus for sperm production.

Many things can wrong with the testes; they can be grouped into physical injury and diseases or conditions that affect the function of the testes:. Other factors that can affect the function of the testes are radiation and chemotherapy used in the treatment of cancer , certain drugs, and disorders of the pituitary gland that stop signals from the hormone endocrine system that trigger production of testosterone from the testes.

These tubules are tightly coiled within the testis, and each testis may contain up to tubules. The tubules are almost 20 inches 50 cm long, and a typical testis contains up to half a mile meters of seminiferous tubules. A fibrous tissue called the tunica covers the tubules. The tunica has three layers: the tunica vasculosa, the inner layer that consists of blood vessels and connective tissue; the tunica albuginea, which encases the testes and connects to the fibers that surround the epididymis, which transports sperm out of the testes and into the penis; and the tunica vaginalis, which contains fluid that reduces friction between the testes and the scrotum.

Besides sperm, testicles also produce male hormones called androgens. Androgens control how the male reproductive system grows, and the development of "masculine" body features such as beards and a deep voice. They also influence sexual functions. Testosterone is the most common form of androgen. It is responsible for the growth of male genitals and sperm production.

Testicles in a healthy male can produce about 6 milligrams of testosterone each day, according to VMC. This isn't always the case, though.

However, "as a man gets older and into his 30s, the amount of testosterone the testis produces starts to drop and continues to decline. Typically, every male is born with two testicles.

They form in the abdomen, and drop into the scrotum during their seventh month of gestation.