Where are sperm made?Sperm is produced in the testes. The testes is a pair of egg-shaped glands, approximately each is 15 to 35 ml in volume. The testes are suspended in the scrotum.
The testes have two major roles, to produce sperm and to produce the male sex hormone, testosterone.
Within the testes are numerous tiny tubes called seminiferous tubules. These tubules can have a total length of 150 meters. Between the tubules lie the Leydig cells, from which the male sex hormone, testosterone comes out. Without testosterone, a man cannot produce sperm. (4)
Scrotum is the skin and muscle containing the testicles. The main function of the scrotum is to keep the testis at a temperature that's lower than that of the rest of the male body. It's an extension of the abdomen, and it's positioned between the penis and anus. Higher temperatures can lessen the sperm count. Through moving the testicles closer to the abdomen when it is cold, and away when hot, the scrotum maintains the perfect temperature within the testes, allowing for a healthy sperm production. The temperature within the testes should be one or two degrees below the body temperature - about 36.8 degrees Celsius or 98 degrees Fahrenheit. (4)
How are sperm made?Spermatogenesis, is the process of sperm production. It's a long and continuous process. Sperms are produced from the seminiferous tubules at different stages of their development. Some sperm are at early stages and others are at later stages of development. It takes roughly 64 days for germ cells to fully develop into a mature sperm that can successfully fertilise an egg. (5)
Within the testes, the cells in the lining of the seminiferous tubules divide over and over again producing sperm. The earliest stage of a sperm cell is called, spermatogonium. As the cells divide and pass through the tubules, they change in shape, from a round cell to the familiar 'tadpole-like' sperm structure. (5)
Mature sperms are released from the testes, and spends 2 to 10 days passing through the epididymis. During this journey, the sperm mature and gain the ability to move or swim.
How is sperm released?Lying at the back of the testes are coiled tubes called the epididymis. When mature sperms are released from the testes, it spends two to 10 days passing through the epididymis, where it develops its ability to move or swim.
The epididymis connects to the vas deferens and when ejaculation starts, sperm are transported from the tail of the epididymis, to the vas deferens, to the urethra in the penis.
During this journey, the sperm passes through different tubes. Each tubes releases its own fluid, it form the mixture called semen. From the seminal vesicles, Cowper's and prostate glands all the fluids are added to the sperm.
About 90% of the ejaculated semen comes from the prostate gland and seminal vesicles. Only a small amount of fluid, which also contains the sperm, comes from the epididymis. (6)
What role do hormones play in sperm production?Hormones from the pituitary gland, control the testes. The pituitary gland releases both luteinizing hormone (LH) and follicle stimulating hormone (FSH) into the bloodstream. Without these hormones the testes cannot perform its function. (4)
During the early stages of puberty, the levels of FSH and LH in the blood rise, so the testes can grow and mature. LH helps the Leydig cells within the testis to produce testosterone, the male sex hormone.
FSH together with testosterone from the pituitary gland acts stimulates the production of sperm.
Besides the development of the genitals, testosterone is also vital for the full development of a young man's body during puberty. It is responsible for the growth and development of other characteristics of the adult male, like, body hair. (8)
What happens in the male organ during ejaculation?Ejaculation starts with waves of muscle contractions that stimulate the transport of sperm. A small amount of fluid plus sperm cells travel from the epididymis through to the vas deferens and passes through the prostate gland and into the urinary tract.
During the process secretions from other parts of the male sex organ form a mixture of fluid that combines with the sperm while it travels on each tract until it reaches the urethra to the tip of the penis where it is discharged at the time of sexual climax. (4)
4. Kimball's Biology Pages, "Sexual Reproduction in Humans".
5. Embryology.ch, "Human Embryology: Spermatogenesis".
6. Wikipedia, "Ejaculation".
8. Eurology Channel, "Testosterone Deficiency".
Discover more about the what, where, how and why of human semen production.