The gubernaculum during testicular descent in the pig fetus.

The role of the gubernaculum during testicular descent was investigated in a study of 119 male pig fetuses obtained at gestational ages ranging from 53 to 116 days. Histologically the gubernaculum was shown to consist of primitive mesenchymal cells with an abundant intercellular material containing glycosaminoglycans (mucopolysaccharides). Rapid descent of the testis through the inguinal canal occurred between 77 and 88 days' gestation, while sustained but slower descent occurred up to 109 days. There was a dramatic increase in the total wet mass of the gubernaculum at the commencement of rapid testicular descent from 77 to 81 days, and a further increase in wet mass during sustained descent from 91 to 95 days. In the period just prior to rapid testicular descent (day 74-81) the percentage increase in the water content of the gubernaculum was larger than the percentage increase in the dry mass. After descent of the testis (day 95-109) there was a decrease in the water content, but also an increase in the dry mass of the gubernaculum. No comparable increase in the water content of umbilical cord or striated muscle tissue occurred during the period of testicular descent. Thus, the marked swelling of the gubernaculum, which dilates the inguinal canal and scrotum and may possibly exert traction on the testis by the force of its expansion, is due largely to an accumulation of water by the gubernaculum. This process may be mediated by the intercellular glycosaminoglycans, since these poly-anionic macromolecules are known to have a large hydrodynamic volume and can act as a "water trap."