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Biology 2nd Baccalaureate

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11.1.2. Spermatozoon

The male gamete

The spermatozoa are cells highly specialized that have decreased in size by eliminating much of the cytoplasm. They are much smaller than eggs and are highly mobile. The sperm are intended to travel to fertilize the female eggThree parts are distinguished in the sperm:

  • Tail. Formed by a flagellum with a protein structure that, when moving, allows the sperm to move.
  • Neck. It contains numerous mitochondria that provide it with the energy to move.
  • Head. It contains the nucleus and the acrosome.
    • The nucleus, with 23 chromosomes, has half the genetic makeup of the rest of the body's cells.
    • The acrosome is a vesicle that contains enzymes that serve to break and cross the protective sheaths of the ovum.

Espermatozoide. Gameto masculino

By Simplified spermatozoon diagram.svg: Mariana Ruizderivative work:Miguelferig [CC0], via Wikimedia Commons

Humor: Homer Simpson sperm.

What path do the sperm follow?

The sperm are formed within the testes and travel to the epididymisWhen they are already mature they pass into the vas deferens. There the fluids produced by the seminal vesicles and the prostate are added to form semenThe spermatozoa constitute only 10% of the sperm, the rest is seminal fluidprostate and other secretions. From the vas deferens it will pass to the urethra and finally to the exterior.

Activity: Parts of a sperm.

Nettie Stevens and the Matilda Effect

Nettie Stevens was the woman who discovered, studying the Tenebrio molitor beetle , that the somatic cells of females had 20 large chromosomes (10 pairs), and those of males, 19 large and one small (9 pairs of large chromosomes and 1 of chromosome one large and one small chromosome).

Stevens concluded that sperm cells containing a small (Y) chromosome determined male sex, and those with 10 large (X) chromosomes determined female sex.


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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.