ANATOMICAL FEATURES 15 



contain the convoluted portions of the seminiferous tubules. From 

 one to three seminiferous tubules are found in each lobule; they 

 may anastomose at their distal ends. The combined length of all the 

 seminiferous tubules approaches 250 meters in the human. The con- 

 voluted portions of the seminiferous tubules empty into the straight 

 tubules (tubuli recti) and these in turn unite with the rete tubules 

 located within the substance of the mediastinum. Connecting with the 

 rete tubules of the testis, there are, in man, from 12 to 14 ductuli 

 efferentes (efferent ductules of the epididymis) of about 4 to 6 cm. 

 in length which emerge from the mediastinum and pass outward to 

 unite with the duct of the epididymis. The epididymal duct represents 

 the proximal portion of the reproductive duct which conveys the male 

 gametes to the exterior. 



4. Specific Structures of the Mammalian Testis Which Produce 

 THE Reproductive Cells and the Male Sex Hormone 



Two very essential processes involved in reproduction are the formation 

 of the sex cells or gametes and the elaboration of certain humoral substances, 

 known as sex hormones. Therefore, consideration will be given next to those 

 portions of the testis which produce the sperm cells and the male sex hormone, 

 namely, the seminiferous tubules and the interstitial tissue. 



a. Seminiferous Tubules 



The seminiferous tubules lie in the septula compartments (fig. 7). The 

 word seminiferous is derived from two Latin words: semen, denoting seed, 

 and ferre, which means to bear or to carry. The seminiferous tubule, therefore, 

 is a male "seed-bearing" structure. Within this tubule the male gametes or 

 sperm are formed, at least morphologically. However, the word semen has 

 a broader implication in that it is used generally to denote the entire repro- 

 ductive fluid or seminal fluid. The seminal fluid is a composite of substances 

 contributed by the seminiferous tubules and various parts of the accessory 

 reproductive tract. 



The exact form and relationship of the various seminiferous tubules (tubuli 

 seminiferi) which occupy each testicular compartment have been the object 

 of much study. It is a generally accepted belief at present that the tubules 

 within each testicular lobule are attached at their distal ends; that is, that 

 they anastomose (fig. 7). Some investigators also believe that there may be 

 other anastomoses along the lengths of these very much contorted and twisted 

 structures. Moreover, it appears that the septula or testicular compartmental 

 partitions are not always complete; the seminiferous tubules of one lobule 

 thus have the opportunity to communicate with those of adjacent lobules. 

 The seminiferous tubules of any one lobule join at their proximal ends and 

 empty into a single straight seminiferous tubule. The straight tubules or 



