What does blood pressure measure in the circulatory system?

Blood pressure measures the pressure of blood in the circulatory system. It indicates the force that the blood exerts against the walls of the arteries as it is pumped by the heart through the circulatory system. Blood pressure readings are typically expressed in millimeters of mercury (mmHg) and presented as two numbers: systolic pressure (the pressure during heartbeats) over diastolic pressure (the pressure when the heart rests between beats).

Understanding blood pressure is crucial for assessing a person's cardiovascular health, as abnormal levels can indicate various health issues, such as hypertension or hypotension.

Focusing on the other options, while respiratory function is vital for overall health, it is not what blood pressure measures. Heart rhythm refers to the pattern of heartbeats and is measured separately, often through an electrocardiogram. Blood volume pertains to the total amount of blood circulating in the body, which also does not directly relate to blood pressure measurements but is instead a factor that may influence blood pressure.