Emergency Medical Technician (EMT) Intermediate Practice Exam

Which organ or tissue requires only intermittent circulation of blood?

1. Liver

2. Kidneys

3. Muscles

4. Brain

The correct answer is: Muscles

Muscles require only intermittent circulation of blood due to their unique physiology and the way they utilize oxygen and nutrients. During periods of rest, muscles do not need a constant supply of blood flow because they can rely on stored oxygen and glycogen reserves for energy. When physical activity becomes more intense, blood flow to the muscles increases significantly to meet the heightened demand for oxygen and nutrients. This adaptive mechanism allows muscles to function effectively during various activity levels without needing continuous blood supply. In contrast, organs like the liver, kidneys, and brain demand a consistent and steady blood supply to maintain their vital functions. The liver performs critical metabolic processes, requires a continuous inflow of nutrients and oxygen, and is heavily involved in detoxification. The kidneys filter blood, regulate fluid balance, and remove waste, all of which necessitate uninterrupted blood circulation. The brain, which is highly sensitive to changes in blood flow, relies on a constant supply to maintain its complex functions, as even a short interruption can lead to significant complications. Thus, the unique characteristics of muscle tissue support intermittent blood flow, especially during varying levels of physical activity, making them the correct choice in this context.