domingo, 5 de junio de 2011

The Male Reproductive System

The male reproductive system is a collection of organs and other structures in the pelvic region. Most of the structures are located outside the body. The male reproductive system has two major functions: producing sperm and secreting testosterone. Sperm are male gametes. Testosterone is the main sex hormone in males. You read about Testosterona in the posts about endocrine system.
Sexual Development in Males
All the reproductive organs are present by birth. However, they are immature and unable to function. The reproductive organs grow very little during childhood and do not mature until puberty.
Puberty is the period during which humans become sexually mature. In the United States, boys generally begin puberty at about age 12 years. The testes produce testosterone that promotes most of the physical changes of puberty
Changes in Males During Puberty
Changes in Reproductive Organs
Testes grow larger Penis grows longer
Other reproductive structures grow Sperm production begins
Other Physical Changes
Pubic hair grows
Facial and body hair grow
Bone density increases
Long bones grow
Muscle mass and strength increase
Bones in face grow
Adam’s apple grows
Apocrine sweat glands develop
Shoulders widen
Voice deepens
Changes in the reproductive organs are called primary sex characteristics. Other changes, that are not directly related to reproduction are called secondary sex characteristics.
Male Reproductive Organs
The male reproductive organs include the penis, testes, and epididymis. Several ducts and glands are also parts of the male reproductive system. These organs are shown in Figure.
The penis is a cylinder-shaped organ. It is the copulatory organ. It contains the urethra. The urethra is a tube that carries urine – excretory system- out of the body and also the sperm – reproductive system-.
The two testes or testicles are the male gonads. They are egg-shaped organs. Their functions are to produce sperm and to secrete testosterone. The testes are contained in the scrotum. As you can see from Figure, the scrotum is a sac that hangs down outside the body. By hanging away from the body, the testes keep sperm at a temperature lower than normal body temperature. The lower temperature is needed for sperm production.
The epididymis is a tube that is about 6 meters long in adults. It is tightly coiled, so it fits inside the scrotum. It rests on top of the testes. The epididymis is where sperm mature. The epididymis also stores sperm until they leave the body.
Other parts of the male reproductive system include the vas deferens that carries sperm from the epididymis to the urethra. The main glands are the prostate and the seminal vesicles. They secrete substances that become part of semen.
Semen is a milky liquid that is ejaculated from the urethra. Semen contains secretions from the glands as well as sperm. The secretions control pH and provide the sperm with nutrients for energy.

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