What does blood pressure measure?

Blood pressure specifically measures the force exerted by circulating blood against the walls of blood vessels, particularly during two key phases of the cardiac cycle: systole and diastole. During systole, when the heart contracts, blood is pumped into the arteries, creating a peak pressure known as systolic pressure. When the heart is at rest between beats (diastole), the pressure in the arteries falls to its lowest point, known as diastolic pressure.

This measurement is crucial for assessing cardiovascular health, as abnormal blood pressure levels can indicate underlying health issues, such as hypertension or hypotension, which can lead to severe complications if not monitored and managed properly.

The other options pertain to different physiological parameters that do not directly relate to blood pressure. For instance, blood circulation speed refers to how quickly blood travels through the circulatory system, while the volume of blood in each heartbeat relates to stroke volume. Additionally, oxygen content of the blood concerns the amount of oxygen carried by the hemoglobin in red blood cells, which is distinct from the mechanical force measured as blood pressure.