4.2 Getting the spermatozoa ready



The ejaculation and the ejaculate


The ejaculation is brought about through rhythmic contractions of the deferent duct that come in waves and through supporting contractions of the pelvic musculature.
The purpose of the coital ejaculation is to deposit spermatozoa, which are largely immobile having come from storage in the cauda of the epididymis, into the rear part of the vaginal cavity, i.e., near the external opening of the cervix, the entrance to the uterus.

While the spermatozoa are pushed through the deferent duct and the urethra, a large volume of secretions of various glands are mixed in. This fluid part of the ejaculate is known as the seminal plasma.

The ejaculate thus consists of up to 10% spermatozoa and 90% seminal plasma for a total volume of 2-6 ml.



The glands involved in the ejaculation


Figure 23 shows the glands that take part in the composition of the seminal plasma. In addition to the secretions of the epididymis (fluid coating of the sperm cells) those of the vas deferens, the prostate and the accessory glands (Cowper's and Littre's) are involved. These secretions are mixed into the ejaculate in a precise, temporal sequence. Fig. 23 - Male sexual glands  Legenda

1
1a
2
2a
3
4
5

6
7
8
9

10

11
Testicle
Efferent ductules of the testis
Ductus epididymidis
Cauda epididymidis
Deferent duct / vas deferens
Ampulla of the deferens duct
Glandula vesiculosa / Seminal
gland
Ejaculatory duct
Prostate gland
excretory duct of the prostate
Bulbourethral gland
(Cowper's gland)
Urethral gland
(Littre's gland)
Urethra

Fig. 23
The male sexual glands that are involved with the ejaculate are marked and highlighted in color. Their secretions come together to form the seminal plasma, which makes up 90% of the ejaculate. (Popup with interactive picture; 138 kB).


The ejaculation represents the second step in the maturation of the sperm cells.
In this process, the motile capabilities of the spermatozoa are abruptly activated. The precise mechanisms of this activation are still unclear. The following factors count, though, as at least contributing:

  1. The mechanical stimulation during the ejaculation.
  2. The admixture of the glandular secretions that
    a) lead to dilution of the sperm cell concentration, and
    b) takes part in the chemical activation.

The result of the interaction of the mechanical stimulation by the ejaculation and the chemical effects of the glandular secretions on the sperm cells correspond with a physiological activation of the sperm cells so that they are ready to go through the upcoming capacitation and the acrosome reaction - both are preconditions for an approach and binding of the spermatozoa to the pellucid zone of the oocyte.

Review

Maturation and activation of the spermatozoa


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