Testicle

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Human male anatomy

Testicles are a part of the male body. They are the part of the body that produces sperm, and hormones, like testosterone. Mammals have two testicles, which are found in a piece of skin near the penis, called the scrotum.

In mammals, the testicles are located on the outside of the body. They hang in the scrotum. They hang by the spermatic cord. This is because making sperm works better at a temperature some lower than the temperature of the body. Scientists call making sperm spermatogenesis.

The cremasteric muscle is part of the spermatic cord. When this muscle contracts (gets shorter), the cord gets shorter. This pulls the testicle closer to the body. When they are closer, they get warmer. So how close the testicles are to the body keeps them the right temperature. If the testicles are too warm, the cremasteric muscle relaxes (gets longer.) This makes the testicles move away from the warm body. Then they can be less warm. This is called the cremasteric reflex. (A reflex is something your body does without you telling your body to do it.) The cremasteric reflex makes the testicles the right temperature. Stress can also make the cremasteric reflex work. If an animal fights it wants its testicles close to the body. This is to make the testicles safe. Scientists believe evolution made the cremasteric reflex happen in fights for this reason. The cremasteric reflex also happens during orgasm.

It is normal for one testicle to be lower than the other. It is normal for the right or left testicle to be the lower testicle. Scientists think this is from evolution. They think it is so one testicle does not hit the other one.

[edit] What do testicles do?

Testicles are like the ovaries in women. They are called homologous. This means they come from the same thing or they look the same. Testicles are part of two organ systems. An organ system is a group of organs in an organism that work together. Testicles are in the reproductive system. The reproductive system lets us make babies. In the reproductive system, testicles are called gonads. (Gonads are the testicles and ovaries. They are the organs that make sperm or ova.) Testicles are in the endocrine system. They are in the endocrine system because they are endocrine glands. A gland is a group of cells that make something and release it (put it outside the cell.) Endocrine means something that is made by cells and released into the blood or tissue. In endocrine glands hormones are released.

The testicles have two purposes:

• Make sperm (spermatozoa)
• Make male sex hormones (Testosterone is the best known male hormone.)

Both purposes are controlled by gonadotropic hormones. These are made by the pituitary gland: The two gonadotropic hormones are:

• luteinizing hormone (acronym) LH
• follicle-stimulating hormone (acronym) FSH

[edit] Structure

The outside of the testicle is the tunica albuginea. This is a hard white coat. Inside are very small tubes called the seminiferous tubules. These tubes are coiled (twisted around.) Inside the tubes are a layer of cells. These cells make sperm cells. This happens after a boy starts puberty. (Puberty is the time when boys and girls become men and women.) The seminiferous tubules go into the epididymis. This is where new sperm cells mature. Then they go into the vas deferens. (This is also called the ductus deferens.) This is the tube that brings sperm to the urethra. (The urethra is a tube where urine comes out of the body.) The hole from the vas deferens to the urethra is the ejaculatory duct.

When a man has sexual desire, the sperm cells go through the ejaculatory duct and into the urethra. The part of the urethra they go through is called the prostatic urethra. The prostate is a gland that makes liquid that the sperm goes in. The prostate also has muscles that push the sperm and fluid into the urethra. This makes a man ejaculate which is when white fluid comes out of his penis with sex. These body parts and the make a man make a woman pregnant (have a baby in her.) This is called having sexual intercourse with her.

This is a picture of the scrotum and testicle cut down the middle. The tunica vaginalis is as big as it can be.

The testicles also make male hormones. (Another way to say male hormones is androgens.) Cells between the seminiferous tubules make androgens like testosterone. These cells are called interstitial cells. They are also called Leydig cells.)

[edit] Testicular size

Testicles can be very big or very small. In mammals testicles are bigger in animals who have many sex partners. Having many sex partners is called being polygamous. Animals that have only one sex partner at a time are monogamous. More sperm is made by animals that are polygamous. If a testicle makes more sperm it is bigger

Most men have testicles that are the same size. They can be different sizes, but they are usually close in size.

In men normal testicles are from 14 cm³ to 35 cm³. Doctors measure the testicles' volume two ways:

• Orchidometer – This is a set of small objects that look like eggs. They are many different sizes. The doctor picks the one that is the size of the testicle. Doctors know what size the orchidometer is. Then they know the size of the testicle.
• Measuring size – with a ruler, calipers, or ultrasound. Then these lengths are used to calculate the volume.

Sometimes the size of the testicles changes.

• Making them smaller:
  • Giving a man testosterone will make them smaller. This is because the testicles do not have to work to make testosterone.
  • Making testicles more warm than usual can make them smaller. When testicles are warm they make less sperm. So if they are warm they get smaller.
  • Testicles can also be smaller if they get injured (hurt.)
• Making them bigger:
  • Giving a man some hormones from the pituitary can make testicles bigger. The pituitary hormones are called gonadotropins. They are hormones that tell the testicles to make sperm and testosterone.

[edit] Health issues

Testicles can be hurt very much if they are hit. This is something people make jokes about.

There are many slang words for testicles. Slang words are other names that are less formal. Some slang words are "balls", "nuts", or in Spanish "cojones". People use slang words for testicles to mean brave or not having fear. People say: He has balls. This means he is brave.

The most important diseases of testicles are:

• Inflammation of the testicles. This is called orchitis
• Testicular cancer
• Fluid around a testicle. This is called a hydrocele
• Inflammation of the epididymis. This is called epididymitis
• Spermatic cord torsion. This is also called testicular torsion. It means when the cord the testicle hangs from twists.
• Varicocele [1] - swollen veins to the testes. Varicocele happens more on the left.

When a doctor removes a testicle it is called an orchidectomy. It is also called an orchidectomy when a doctor removes both testicles. This is also called castration. In the past, people castrated boys before puberty. They did this so the boys voices would not change. These boys were called castrati.

If a man loses a testicle doctors can help. Doctors can put in a testicular prosthesis. This is a false testicle. It is put in the scrotum. It looks and feels like a testicle. If both testicles are lost, a man cannot have a baby. He also does not have enough testosterone. To stay healthy, he must take testosterone medicine.

[edit] Other names

There are other names for testicle. These are sometimes vulgar. (Vulgar is from Latin vulgus. This means from common people. So vulgar is something rude or not very nice.) Some vulgar words for testicle are:

• Balls
• Nuts
• Nads

[edit] See also

• Cryptorchidism (cryptorchismus)
• Infertility
• List of homologues of the human reproductive system
• Orchidometer
• Spermatogenesis
• Sterilization (surgical procedure), vasectomy