Vitiligo Definition and Overview. Vitiligo is an autoimmune skin disease in which there is a progressive destruction of the skinâs pigment-producing cells (melanocytes), resulting in areas of otherwise normal white skin devoid of melanin pigment. It is not unusual for hairs growing in areas of vitiligo to lose their normal color.
Sperm Cycle. Old sperm cells die off and new cells are created at a rate of about one percent each day. This means the entire sperm cycle requires approximately 100 days. The final 75 days represent a period of maturation for the sperm cell. This final step of sperm maturation, called spermiogenesis, puts the fuel into the tank and completes the development of the sperm cell (spermatozoon).
The Male Reproductive System The main role of the male reproductive system is to make and deliver sperm. The testes are the main organs of the male system. Two testes are held in an external sac called the scrotum. The testes make sperm in tiny tubes called seminiferous tubules.The sperm mature and are stored in an epididymis. A tube called a vas deferens carries sperm from each testis to the urethra within the penis.Along the way, secretions of several glands form a nutrient-rich fluid called seminal fluid.he sperm mature and are stored in an epididymis. A tube called a vas deferens carries sperm from each testis to the urethra within the penis. Along the way, secretions of several glands form a nutrient-rich fluid called seminal fluid.