Procreation

The human procreation is the whole of the processes by which an individual of male sex and an individual of the female sex generate a new individual.

Regulation of the function of reproduction at the man

The testiculaire activity: a double functionality

Production of spermatozoa

  • the spermatogenèse is exerted in the seminiferous tubes (hundreds of wound into a ball tubes). In the wall of these tubes, germinal cells stocks undergo many mitoses (cellular divisions with identical) and a meiosis (division leading to the futures gamètes containing the gentic half of the inheritance) centripetal.
  • the spermatozoa are released in the light of the tube then gain the épididyme where they acquire their mobility and their capacity to fertilize the ovule. This stage is called capacitation. They mix during ejaculation with secretions prostate sufferers and seminal (80% of volume) to form sperm. The spermatozoa are cells specialized in their function of reproduction. Indeed, they contain only organoids essential to their function: to transfer male genetic information inside the gamète female.
  • the testosterone produced by the interstitial cells of Leydig stimulates the spermatogenèse while being fixed on the cells of the wall of the seminiferous tubes. The cells of Sertoli (role of support and nutrition) secrete a protein essential to the fixing of testosterone on the seminiferous tubes.

The testosterone synthesis

  • the testosterone, only male hormone testiculaire of the adult, is secreted locally and in blood circulation.
  • It is active in very minor amount, is secreted in a pulsatile way, by pulsate of a few minutes (spaced periods of nonsecretions). But the testosteronemy oscillates around an overall constant value.
  • It stimulates also the spermatogenèse on the level of the tubes seminiferous and causes the installation and the maintenance of the secondary sexual characters starting from puberty.
  • Note:: In certain mammals, the testosterone is secreted in great quantity during particular periods.

The hormonal control of the operation of the testicle: 3 levels of control

Role of the handle-pituitary gland

  • pulsate Them of testosterone are started by pulsate of LH (Lutéinisante Hormone). The pulsatility of LH is essential has pulsatile testosterone secretion.
  • the FSH (FolliculoStimulante Hormone) stimulates the cells of Sertoli has to synthesize a protein (APB) essential to the fixing of testosterone on the wall of the seminiferous tubes.
  • the handle-pituitary gland thus controls, indirectly, the spermatogenèse thanks to these two gonadostimulines.

Role of the hypothalamus

  • Under the influence of certain external environmental factors (luminosity, T°) and interns (adrenalin) of the neurons hypothalamic secrete pulsatile a GnRH neurohormone in manner which starts pulsate them of LH and FSH

Role of the testicle itself: rétrocontrôle negative

  • maintains It of an overall constant testosteronemy is ensured by a negative rétrocontrôle (or negative feedback) exerted by testosterone on the CHH (there thus exist receivers with testosterone) when the testosteronemy exceeds a value threshold.
This rétrocontrôle negative armature a dimunition of the production of GnRH and thus of LH what causes a reduction in the production of testosterone. This makes it possible to keep the testosterone rate in the neighborhoods of 5ng/l.

Regulation of the function of reproduction at the woman

Operation

The hormonal control of operation

See too

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