Final answer:
The major difference is that local causes of testicular atrophy usually affect only one testicle and may be reversible, whereas systemic causes tend to involve both testicles and can be a result of more widespread body issues, which might be more difficult to reverse.
Step-by-step explanation:
The difference between local and systemic causes of testicular atrophy primarily lies in the scope and origin of the issue. Local causes pertain to conditions or traumas affecting the testes directly and may include physical injuries sustained during sports or infections restricted to the testicular area. These local issues might affect only one testicle and have the potential to be reversible, especially if treated promptly.
On the other hand, systemic causes relate to conditions affecting the entire body or multiple organ systems which consequently impact the testes. Such conditions include hormonal imbalances, genetic disorders, or diseases that impair blood flow or nerve function. Systemic issues often affect both testicles and may be more challenging to reverse because they involve broader bodily dysfunction.
While there are exceptions, systemic conditions are generally not trauma-related, as the student's question implies, while local causes could include trauma such as a sports injury or localized diseases like orchitis. Neither local nor systemic causes include a definitive rule about reversibility, as it depends on the severity and duration of the condition affecting the testes.