TABLE OF CONTENTS
Thermoregulation of Testis in Animals: Mechanisms and Anatomy Adaptations
Thermoregulation of testis (testicular thermoregulation) is the process by which the testis maintains a temperature lower than body temperature using structures like the scrotum, muscles, and blood vessels to support sperm production.
For effective functioning, the testes have to be kept at a temperature of 4-6°C lower than the body temperature.
The structures involved in the thermoregulation of the testis include:
- Scrotal Skin and Sweat Glands
- Dartos Muscle
- External Cremaster Muscle
- Pampiniform Plexus
- Tunica Albuginea
1. Scrotal Skin and Sweat Glands
The scrotal skin and sweat glands contain temperature receptors. When there is an elevated environmental temperature, these receptors trigger a response by inducing panting and sweating, thereby lowering body temperature.
The scrotal skin lacks subcutaneous fat and is enriched with large adrenergic sweat glands. Sweating enables the scrotum to cool down through evaporative heat transfer.
2. Dartos Muscle
Dartos muscle is an open, mesh-like smooth muscle layer that lies beneath the scrotal skin. By contracting in cold weather to hold the testes against the body and by relaxing in warm weather, it acts as the principal thermoregulator of the testis.
The contractile characteristics of the dartos are androgen-dependent, and its ability to contract in cold climates is lost in castrated males.
3. External Cremaster Muscle
The external cremaster muscle raises the testis, thereby playing a role in the testicular thermoregulation.
It contracts and relaxes, creating a ‘pumping action’ on the pampiniform plexus, thus facilitating blood flow and enhancing cooling efficiency.
4. 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.
5. Tunica Albuginea
Tunica albuginea 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°C. In bulls, it is 4°C, and in rams, it is 5-7°C.
These anatomical arrangements of the testis and features of the testicular blood vessels maintain the testicular temperature.
