A sphygmomanometer is a medical instrument used to measure blood pressure in which type of blood vessels?

Introduction / Context:
Blood pressure is a vital sign that indicates the force exerted by circulating blood on the walls of blood vessels. A sphygmomanometer is the standard device used in clinics to measure blood pressure. This question checks whether you know in which type of vessel this pressure is primarily measured.

Given Data / Assumptions:

• The instrument named is a sphygmomanometer.
• Options include veins, arteries, eye vessels, and synovial cavities of joints.
• We assume standard clinical procedure for measuring systemic blood pressure in humans.

Concept / Approach:
Systemic blood pressure is conventionally measured in a large artery, most often the brachial artery in the upper arm. This arterial pressure reflects the force generated by the heart during systole and diastole. Veins, by contrast, have much lower pressures, and synovial cavities do not contain blood, only synovial fluid. Eye pressure is measured by a different device (tonometer) and is not what is meant by “blood pressure” in routine medical practice. Therefore, the correct answer must be arteries.

Step-by-Step Solution:
Step 1: Examine option A, veins. Although veins carry blood back to the heart, their pressure is low and not typically measured with a sphygmomanometer.Step 2: Examine option B, arteries. Clinically, blood pressure readings such as 120/80 mm of mercury refer to arterial pressure, measured using a cuff on the arm over the brachial artery.Step 3: Examine option C, vessels of the eyes only. Intraocular pressure is measured by a different device, not a sphygmomanometer.Step 4: Examine option D, synovial cavities. These cavities contain synovial fluid, not circulating blood, so blood pressure is not measured here.Step 5: Conclude that arteries are the correct type of vessels involved in sphygmomanometer readings.

Verification / Alternative check:
A typical blood pressure measurement involves placing a cuff around the upper arm, inflating it to temporarily stop blood flow through the brachial artery, and then listening with a stethoscope or using a digital sensor as the pressure is slowly released. This process directly relates to arterial pressure. No similar routine procedure exists for venous or synovial pressure using a sphygmomanometer, confirming the correct answer.

Why Other Options Are Wrong:
Option A is wrong because venous pressure is not normally measured with a sphygmomanometer and is much lower than arterial pressure. Option C is wrong because eye pressure (intraocular pressure) is a different physiological parameter measured with a tonometer. Option D is wrong because synovial cavities are part of joints and contain joint fluid, not circulating blood.

Common Pitfalls:
Students sometimes think of “blood pressure” as a general property of all vessels and may forget that clinical blood pressure refers specifically to arterial pressure. Another pitfall is confusion between different clinical instruments and measurements, such as mistaking intraocular pressure for systemic blood pressure. Remember that when you see a sphygmomanometer and a cuff on the arm, it is always arterial blood pressure that is being recorded.

Final Answer:
Arteries.