Fine structure of muscle cells of the human testicular capsule: basis of testicular contractions.

Electron micrographs of human testicular capsule reveal large numbers of branching smooth muscle cells coursing through collagenous tissue of the tunica albuginea. These cells have subcellular morphology characteristic of smooth muscle cells, and they associate with one another through areas of close contact. These are the contractile cells responsible for spontaneous contractions of the human testicular capsule-contractions that may be important in transporting nonmotile sperm out of the testis.