Testicular Descent (Descent of the Testis) in Animals

Testicular descent is the process in which the testes move from their original position in the abdominal cavity, pass through the inguinal canal, and reach the scrotum, occurring during fetal development or shortly after birth, depending on the species.

This descent is regulated by the action of the gubernaculum, intra-abdominal pressure, and fetal androgens, and is essential for normal testicular function and fertility.

The descent of the testis is also known as testicle drooping.

Physiological Mechanism

The descent of the testes into the scrotum is facilitated by several anatomical and hormonal factors during fetal development.

These factors work in coordination to ensure proper positioning of the testicles necessary for normal reproductive function.

• Enlargement of the gubernaculum and its disappearance play an important role in testicular descent.
• Intraabdominal pressure in the fetus also determines testis descent.
• Androgen from fetal testis favors testis descent.

Developmental Stages

1. Transabdominal Phase: Initially, the testes are located near the kidneys. The process of descent begins here.
2. Inguinoscrotal Phase: During this phase, the testes pass through the inguinal canal and start their final descent into the scrotum.
3. Postnatal Descent: In some species, such as dogs, the descent continues shortly after birth.

Normal Time of Descent of the Testis

• Horse – 9–11 months of gestation
• Cattle – 3½ to 4 months of gestation
• Sheep and Goat – 2½ to 3 months of gestation
• Swine – 3 months of gestation
• Dog – Approximately 5 days after birth

Failure of testis to descent into the scrotum is called as cryptorchidism. The retained testis is called as cryptorchid testis.

Factors Affecting Testicular Descent

• Genetic Factors: Certain genetic mutations may delay or prevent the descent of the testes. This condition may be observed in specific breeds or populations.
• Hormonal Imbalance: Insufficient androgen production or an imbalance in hormones like INSL3 can affect testicular descent. This is common in animals with hypothyroidism or other hormonal disorders.
• Temperature Sensitivity: Temperature can affect testicular development and descent, especially in species living in extreme environmental conditions.