Answer:
External- The testes are covered by a tough membranous shell called the tunica albuginea. Within the testes are very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells (germ cells) that develop from puberty through old age into sperm cells (also known as spermatozoa or male gametes).
Internal -Each testicle is covered by tough, fibrous layers of tissue called the tunica. The outer layer is called the tunica vaginalis and the inner layer is called the tunica albuginea. ... There are about 800 seminiferous tubules tightly coiled within each testicle.