The structure and function of the epididymis. 2. The histogenesis of the rat epididymis.

Abstract

Observations were made on the epididymides of young white rats of the following ages: 3, 21, 28, 32, 37, 39, 56, 72, 96, 110 days. Both efferent ducts and epididymal duct are undifferentiated at 21 days with a similar cuboidal epithelium. The connective tissue coat of the efferent ducts is one cell thick whereas that of the epididymal duct is two or three cells thick. The possible involvement of the connective tissue in the process of histogenesis is discussed. Differentiation within the epididymal duct commences at 28 days when the epithelium in the cephalic portion is tall and that in the caudal portion of the head and remainder of the tail is tall with isolated segments of low columnar epithelium. The latter epithelium is associated with a wider lumen which evidently becomes continuous down the duct. In the efferent ducts at this stage ciliated cells have appeared. Differentiation of the cephalic portion of the head is completed rapidly by the 37th day but that of the caudal portion of the head and tail of the organ is completed only at the 96th day. In certain zones, histodifferentiation is accompanied by obvious nuclear differentiation. Spermatozoa first appear in the testis at 56 days but do not enter and fill the epididymal ducts until 72 days. There is evidence of an outflow of fluid from the testis which carries spermatocytes and spermatids into the duct at 32 days. The changes in the epithelium of the efferent duct, the epididymis, and the deferent duct from the 3rd to the 110th day are tabulated.