OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Why are extremities cooler than the core of the body?

1. They have a larger surface area compared to their size

2. They are made of less dense tissues

3. They contain less blood than the core

4. They are farther from the heart

The correct answer is: They have a larger surface area compared to their size

The correct answer highlights the relationship between surface area and heat loss in the body. Extremities, such as hands and feet, have a larger surface area relative to their volume compared to the body's core. This increased surface area allows for more heat to be dissipated into the environment through processes such as radiation, conduction, and convection. As a result, these areas tend to be cooler than the core, which is insulated by body tissues and maintains a higher temperature to support vital organ functions. While the other options mention relevant factors, they do not fully account for the primary reason. For example, the density of tissues does not necessarily influence temperature directly, and while extremities might contain less blood at times, the core maintains a higher volume of warm blood to keep its temperature stable. The distance from the heart can affect blood flow, but the fundamental reason for the temperature difference remains the larger surface area of the extremities, which facilitates greater heat loss.