If an adult human male has two functional testes, what is the total estimated range of seminiferous tubules present in his body?

Each testis contains about 250 testicular lobules, and each lobule contains 1 to 3 highly coiled seminiferous tubules. Thus, one testis has \( 250 \times (1\text{ to }3) = 250\text{ to }750 \) tubules. Therefore, in both testes combined, there are \( 500\text{ to }1500 \) seminiferous tubules.