4.2 Getting the spermatozoa ready

Spermatozoa maturation steps


Quiz 19

There are parallels between getting the spermatozoa ready and the maturation of an oocyte but there are also clear differences.

The spermatozoa have to go through several temporal maturation steps in a series of different locations in order to be capable of penetrating into the oocyte. While the oocyte's maturation steps involve the storing of yolk and the process of meiosis, functional maturation steps are required with the spermatozoa, which mainly involve their motile abilities along with their ability to penetrate through the egg covering. Fig. 20 - Normal spermatozoon  Legend


Fig. 20
Normal spermatozoon with head and tail. In the head a light cap is visible, the so-called acrosome. The somewhat thicker beginning part of the tail (mid piece) contains the mitochondria.

The spermatozoa experience an initial maturation step during the time they are "stored" in the epididymis. When the ejaculation occurs, a second step follows that leads to a sudden activation of their motility.
The third step takes place during their stay in the female genital tract, especially during the ascension towards the ovary through the uterus and fallopian tube. The spermatozoa experience thereby the so-called capacitation. Finally, the last activation step follows: the acrosome reaction in the immediate vicinity of the oocyte.

The maturation and activation of the spermatozoa occur in the following four steps:

Storage in the epididymis Maturation
Ejaculation Activation
Ascension to the ovary Capacitation
Near the oocyte Acrosome reaction

The above sequence, from the maturation in the epididymis to the acrosome reaction near the oocyte, is in vivo a precondition for spermatozoa to be optimally able to fertilize. Only a spermatozoon that has undergone an acrosome reaction is capable of binding to the pellucid zone of the oocyte. (Further commentary).

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