Histology of the normal and retained equine testis.

This research study aimed to understand the differences in the structure and function of horse testes in various locations – the abdomen, the inguinal area (groin), and the scrotum. The findings revealed distinct differences in the testes with regards to the number of spermatogenic cells and their development status, diameter of the seminiferous tubules, and number and condition of the Leydig cells found in these various locations.

Research Methodology

• The researchers examined the testes of horses located in different body areas: the abdomen (abdominal testes), the groin area (inguinal testes), and the sac that contains the testicles (scrotal testes).
• Both a general examination (gross examination) and a more detailed examination using light microscopy were carried out on the samples.

Findings on Spermatogenic Cells and Seminiferous Tubules

• An average of 1.5, 2.3 and 4.6 layers of spermatogenic cells (cells responsible for sperm production) were recorded in the abdominal, inguinal and scrotal testes, respectively.
• Also, the diameters of the seminiferous tubules (tubules within the testes where spermatogenesis occurs) were found to be about 66.2, 83.6 and 146.6 microns in size in the abdominal, inguinal, and scrotal testes respectively.

Findings on Interstitial Spaces and Leydig Cells

• The spaces between tissues and organs in the body, known as interstitial spaces, and the number of interstitial cells (of Leydig, cells which produce testosterone) seemed to be increased in the testes that have not descended (retained testes).
• Spermatogenesis, or the process of sperm production, appeared to be halted in these retained testes.

Findings on Spermatogenic Cells in Retained Testes

• The researchers found that the most advanced form of spermatogenic cells in the retained testes were early spermatocytes, demonstrating that sperm production is stalled in early stages in these testes.
• There was also substantial vacuolation (formation of cavities or cell voids) observed in the spermatogenic cells of these undescended testes.

Possible Cause of These Changes

• The changes noticed in the structure and function of the retained testes could result from the higher temperature of the abdominal environment, which is not conducive for sperm production and its development and the altered production of androgens (a type of hormone that plays a role in male traits and reproductive activity).