Which of the following is NOT one of the five functions of the skeletal system?

The five primary functions of the skeletal system include support, movement, protection, storage of minerals, and blood cell production. The correct answer identifies a function that does not categorically belong to the skeletal system.

Support is important as bones provide structure to the body. Movement is facilitated by the skeletal system in conjunction with muscles, as bones serve as levers that muscles pull on. Storage of minerals, specifically calcium and phosphorus, is another crucial role, as bones store these essential minerals and release them into the bloodstream as required. Similarly, the skeletal system is vital for producing blood cells, particularly within the bone marrow.

In contrast, while the skeletal system may play an indirect role in defense through its protective functions (such as enclosing vital organs), defense is not considered one of the five primary functions. Therefore, identifying defense as not being one of the primary functions of the skeletal system accurately reflects the established understanding of anatomy and physiology.