Final answer:
Damaged muscle tissue releases both myoglobin and potassium, potentially leading to myoglobinuria and hyperkalemia, respectively.
Step-by-step explanation:
The substance that is released by damaged muscle tissue includes both myoglobin and potassium. When muscle tissue is damaged, it can cause a release of myoglobin, a protein that binds oxygen in the muscle, into the bloodstream. This can be detected as a sign of muscle damage. Additionally, damaged muscle may also lead to the release of potassium into the extracellular fluid (ECF), contributing to a condition known as hyperkalemia, which is an elevated potassium blood level that can impair the function of skeletal muscles, the nervous system, and the heart.