How do testicles descend in dogs? - briefly
In dogs, testicular descent begins prenatally and is typically completed by birth. This process is facilitated by the hormone dihydrotestosterone (DHT) which stimulates the development of the inguinoscrotal swellings into the scrotum, allowing the testicles to descend into their final position.
How do testicles descend in dogs? - in detail
The descent of testicles in male dogs is a complex process that involves several stages and factors, including hormonal influences and anatomical changes. This developmental journey begins during the fetal stage and continues through puberty.
In the early stages of fetal development, both male and female puppies have undescended gonads, which are located near the kidneys. In male dogs, these undifferentiated gonads develop into testes under the influence of specific genes and hormones. The testes initially lie in the abdominal cavity, connected to the kidneys by a structure called the mesonephric duct.
As fetal development progresses, the testicles begin their descent from the abdomen towards the scrotum. This migration is guided by several factors:
- Hormonal Influences: Androgens, particularly testosterone, play a crucial role in initiating and maintaining the descent of the testicles. These hormones are produced by the fetal testes and act on specific receptors to stimulate the growth of the gubernaculum, a ligament-like structure that guides the testicular descent.
- Anatomical Changes: The inguinoscrotal ring, which is initially closed during early fetal development, begins to open under the influence of hormones and mechanical forces exerted by the growing testes. This allows the testicles to move from the abdomen into the inguinal canal and eventually into the scrotum.
- Gubernaculum: The gubernaculum is a fibrous cord that attaches the developing testis to the scrotum. As the testicle grows, it pulls on the gubernaculum, which in turn guides the testis towards its final position in the scrotum.
The descent of the testicles typically occurs in two stages:
- Transabdominal Phase: During this phase, the testicles move from their initial position near the kidneys to the inguinal region, guided by the gubernaculum and hormonal influences. This phase is usually complete by the time of birth.
- Inguinoscrotal Phase: In this phase, the testicles descend through the inguinal canal into the scrotum. This phase can continue postnatally, with some puppies completing their descent within a few weeks after birth, while others may take several months.
Any disruption in this intricate process can lead to cryptorchidism, a condition where one or both testicles fail to descend into the scrotum. This can have significant health implications for the dog, including increased risk of testicular cancer and infertility. Therefore, it is essential for veterinarians and pet owners to monitor the descent of the testicles in male dogs and address any concerns promptly.