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Sperm Terms: How Many Do You Know?

Posted November 7, 2014 by Cynthia

Every individual sperm cell – also known as a spermatozoan (Greek for sperm animal) -- has just one specific goal: arrive at an awaiting egg (or ovum) before any other sperm, and be the first one to penetrate and fertilize it. Let's see how this happens:sperm_(1)

Sperm Anatomy

A normal sperm cell is comprised of a head, a neck, and a tail. Abnormalities of any of these structures can make it difficult for the sperm to reach its goal.

  • The head of each sperm cell contains the nucleus which holds the genetic contribution from the male: one copy of each chromosome, including a sex chromosome which will determine whether the resulting fetus is male or female. The sperm head is covered by the acrosome which contains enzymes that assist the sperm to penetrate the surface of the egg so that the egg can be fertilized.

  • The neck or midpiece of the sperm cell is essentially a sheath that surrounds the uppermost portion of the tail closest to the head. This sheath contains mitochondria, the energy-producing cellular components that help propel the tail of the sperm.

  • The tail, also known as the flagellum, measures up to ten times longer than the head. Its filaments, with the help of the mitochondria in the midpiece, enable the sperm to move through the female reproductive tract, toward the egg to accomplish fertilization.

Sperm Production & Transport

Once puberty begins in a young male, spermatogenesis (sperm production) commences. From then on, sperm are continually being produced. One sperm cell takes about 70 days to fully mature.

  • Sperm cells develop in the testes, specifically, within the seminiferous tubules. They move to the epididymis to fully mature and are stored there.

  • During ejaculation, mature sperm move from the epididymis through the vas deferens, to the ampulla, where secretions from the seminal vesicles are added.

  • Muscular contractions allow seminal fluid to be propelled forward through the ejaculatory ducts toward the urethra, passing first by the prostate gland, where a milky fluid is added to form semen.

  • Finally, the semen is ejaculated through the far end of the urethra and out the end of the penis.

Final delivery

Successful fertilization depends on many factors including normal sperm counts, normal sperm morphology and motility, and just the right timing.

  • In the teaspoon or so of semen that is ejaculated, there may be up to 300 million sperm.

  • Fresh sperm can survive for a few days in a woman's reproductive tract.  A fraction of those sperm will manage to reach an available egg. Ultimately, only one sperm cell will succeed in fertilizing it.

  • Sperm banks store donated sperm in liquid nitrogen tanks where it can remain frozen for extended periods of time. To optimize reproductive outcomes for their clients, sperm banks recruit donors with higher than average sperm counts and highly motile sperm.

 Photo Credit: wellcomeimages

 

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