What is the primary function of blood in the body?

The primary function of blood in the body is transporting nutrients and oxygen. Blood acts as a vital transportation system, delivering essential substances that are crucial for the survival of cells and tissues. Oxygen, which is carried by red blood cells, is necessary for cellular respiration, allowing cells to produce energy. In addition to oxygen, blood also transports nutrients absorbed from the digestive system, including glucose, amino acids, and fatty acids, to various tissues throughout the body.

Furthermore, blood plays a key role in removing waste products, such as carbon dioxide and urea, which are byproducts of cellular metabolism. This ability to transport substances effectively allows blood to maintain homeostasis, supporting overall body function and health. The other options focus on functions that are not primarily associated with blood; for instance, insulation and cushioning are mainly roles of adipose tissue, structural support is provided by the skeletal system, and storing fat and energy is related to adipose tissue rather than blood. This clarification emphasizes why blood's transport function is so crucial to human physiology.