Physiology of testicular thermoregulation For the Eskimo called sperm

In a continent called Man, there lives a cold blooded prince, an Eskimo of some sort, called Sperm. In its childhood and formative years, it requires a relatively cold environment for optimal growth and function; excessive heat would interfere with its production, growth and development. Unlike its counterpart, the warm blooded Queen called Egg or Ova, which lives in the Tropics [inside the body, where it is warm] of another continent called Woman, he [the Prince] has to live in the temperate regions, in the Arctics, in a specialized Igloo with a lot of mechanisms in place to maintain its delicate temperature.
How does it achieve this features?

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TESTICULAR THERMOREGULATION
Thermoregulation or heat regulation is the process of maintaining temperatures within optimal limits. A suitable environmental temperature is maintained for the Eskimo by means of the following:
THE IGLOO
The Igloo, that is the Testes, where the Eskimo lives, is placed in the Arctics [cold region], that is outside the body, where it is subject to cooling from the combined effect of circulating air and the ambient,environmental temperature.
This is a sharp contrast to the Ovaries which are placed inside the body, away from environmental influences, and subject to warming by the core body temperature.

NO FIRE PLACE, NO HEAT WARMERS.
Most parts of the body has a self warming mechanism constituted by a heat generator and a heat retainer. Heat is generated by the metabolic activities of the body, and is entrapped by the thick layer of fat beneath the skin which acts as an insulator preventing excessive heat loss to maintain warmth. But in the testes, there's simply no fire place, or heat warmer; the skin of the Scrotum is thin and completely devoid of fat, thus allowing for generous heat losses so as to maintain a relatively cool environment for the sperm.

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THE COUNTERCURRENT HEAT EXCHANGER.
The testes is supplied nutrients by a single pipe the testicular artery, and wastes from it is carried away by numerous pipes the Pampiniform plexus of Veins. The two system of pipes are arranged in such a way that the supplying pipe is in the middle, and is surrounded by waste pipes in a circular fashion, with the arrangement looking more like a piston set. This arrangement creates an effective countercurrent heat exchanger with the result that the warm blood, from the core of the body, being supplied to the testes, is cooled down by the cold blood returning from the testes and in the opposite direction. That is, as warm blood is being supplied to the testis, cold blood from the testis is returning back to the body. They both meet halfway, and there's a heat exchange warmth is exchanged for cold, and cold for warmth. At the end of the day, the supplies getting to the testes is relatively cold, and the temperature is maintained.

WHEN THERE'S TOO MUCH COLD
Even though the sperm loves cold environment, too much cold, ice freezing cold, is still not good for it's health. Hence when there's such cold, it closes the window blinds and goes inside.
This it does by means of the Cremaster and Dartos muscles; the Dartos contracts wrinkling the skin of the scrotum, reducing the surface area, and hence reducing heat loss, thats is closing the blinds, and the Cremaster pulls the Testis up, nearer to and into the body, that is going inside to avoid catching cold. Some amazing physiology! And they would have me believe it was all by chance, the random throw of a roulette, the result of a chaotic big bang.

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CONCLUSION
Exposing the Scrotum/Testis to too much heat for long periods of time can interfere with sperm production, denature already produced sperm cells, and thus can lead to male infertility.
Hence males are advised against the following:

• Wearing tight fitting pants, especially those made of nylon materials.
• Placing laptops on one's lap for long periods of time while using them.
• Having hot baths in Jacuzzis habitually, and for long periods if time.
• Baking, staying near an oven with the scrotum unprotected for long periods of time.Etc
  Nature worked so hard to keep the testis cool, don't let all that hard work go to waste!

REFERENCES

• Wikipedia : Testicle

• Wikipedia : Male reproductive system

• wikipedia : Community of Igloos

• Wikipedia : Sperm

Thank you for reading