Which of the following is NOT a function of capillaries?

Capillaries are the smallest blood vessels in the body and play a crucial role in various physiological functions. They are primarily responsible for nutrient delivery, waste removal, and gas exchange. This is achieved through their thin walls, which allow for efficient diffusion of substances between the blood and the surrounding tissues.

Nutrient delivery occurs in capillaries when oxygen and nutrients are delivered from the blood to the cells. Similarly, during waste removal, metabolic waste products such as carbon dioxide and urea move from the cells into the capillaries where they are carried away for elimination. Gas exchange refers to the process where oxygen is absorbed into the blood and carbon dioxide is released from the blood at the level of the capillaries in the lungs and other tissues.

The destruction of antigens, however, is a function primarily associated with the immune system, specifically with cells such as macrophages and lymphocytes that can operate in tissues and lymphatic systems. Capillaries do not have a role in the direct destruction of antigens; instead, they facilitate the transportation of immune cells to sites of infection or inflammation. Thus, this option accurately describes a function that is not performed by capillaries.