Which vital sign assesses the functioning of the body's resistance system?

Blood pressure is the vital sign that primarily assesses the functioning of the body's resistance system. Blood pressure reflects the force exerted by circulating blood on the walls of the arteries, which is influenced by several factors including blood volume, cardiac output, and the resistance offered by the blood vessels—known as vascular resistance.

The body maintains blood pressure within a narrow range, which is crucial for ensuring adequate blood flow to organs and tissues. When assessing blood pressure, one can infer about the state of vascular system health and the body's ability to regulate blood flow, particularly under varying conditions.

In contrast, heart rate provides information primarily about the rate at which the heart beats, rather than resistance. Respiratory rate measures how many breaths a person takes and is more related to respiratory function and metabolic needs rather than vascular resistance. Temperature reflects the body’s ability to regulate heat and overall metabolic processes, but does not directly indicate information about the resistance system of blood vessels. Thus, blood pressure stands out as the key vital sign related to the assessment of the resistance system.