Cardiovascular System

The best answer is the historical use of liquid mercury (hydrogyrum) to measure pressure. The reason that Hg was used is as stated in choice A.

Turbulent blood flow generates audible sound that can be heard with a stethoscope placed on the skin above the heart. Such turbulent flow is produced when blood flow out of the heart is impeded by the cusps of the semilunar valves as they close.

1 mmHg ~ = 1.34 cmH₂O, so 100 mmHg ~ 134 cmH₂O.

Pressure is inversely proportional to the volume, so if volume decreases, the pressure will increase. Boyle’s law applies to gas at a constant temperature.

The extrinsic and intrinsic pathways form “prothrombinase” (also called prothrombin activator) from factor X.

When standing, there is a column of blood filling the posterior tibial artery (PTA) that rises up to the aorta. The column is about 130 cm tall for a man of about 1.75 m in height. This “head” of liquid exerts a hydrostatic pressure on the wall of the PTA that is in addition to the systolic pressure produced by the pumping action of the left ventricle. A column of 130 cm of blood exerts a pressure of about 100 mmHg (1 mmHg = 1.36 cm H₂O) which is in addition to the 115 mmHg original systolic value.

Radial pulse because we are palpating the radial artery at that position.

The “bar” was used as unit of air pressure: 1 mb = 1 hPa. It is now used as a prefix in a word to denote an association with pressure. A barometer is a device to measure air pressure; hence baroreceptor refers to a pressure receptor.

MAP = CO × TPR, so CO = MAP ÷ TPR

QRS is produced when the cells of the ventricles depolarise.