Veterinary Andrology and Reproductive Techniques

THERMOREGULATION OF TESTIS

• For effective functioning, the testes have to be kept at a temperature of 4-6° C lower than the body temperature.

Scrotal skin and sweat glands

• It has got temperature receptors. When there is a elevated environmental temperature, these receptors elicit the response by producing panting and sweating and lower the body temperature.
• Scrotal skin is devoid of subcutaneous fat.
• It is enriched with large adrenergic sweat glands.
• Sweating allows scrotum to be cooled by evaporative heat transfer.

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Dartos muscle

• It is an open mesh like smooth muscle layer which lies beneath the scrotal skin.

By contracting in cold weather to hold the testes against the body and by relaxing in warm weather, it is the principal thermoregulator of the testis.

• The contractile characteristics of dartos are androgen dependant and its ability to contract in cold climates is lost in castrated males.
• Action of dartos muscle in stallion is enhanced by presence of smooth muscle in the spermatic cord and tunica albuginea.

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External cremaster muscle

• It raises the testis, thereby playing a role in the thermoregulation of testis.
• It contracts and relaxes, creating a ‘pumping action’ on the pampiniform plexus, thus facilitating blood flow and enhancing cooling efficiency.

Pampiniform plexus

• In the proximal end of testis, testicular artery is coiled and is surrounded by network of spermatic vein. This arrangement is called as pampiniform plexus.
• Blood present in vein cools the incoming blood of artery.

Tunica albuginea

• It is richly supplied with network of blood vessels and plays role in regulation of testicular temperature
• In human beings, the difference between body temperature and testicular temperature is 2^oC.
  • In bulls : 4^oC
  • In ram : 5-7^oC

The anatomical arrangement of testis and features of testicular blood vessels maintains the testicular temperature

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