Unit Four

tissues in affected regions typically become edematous and painful.

Heredity, pregnancy, obesity, and standing for long periods raise the risk of developing varicose veins. Elevating the legs above the level of the heart or putting on support hosiery before arising in the morning can relieve discomfort. In travenous injection of a substance that destroys veins (a sclerosing agent) or surgical removal of the affected veins may be necessary. ■

tissues in affected regions typically become edematous and painful.

Heredity, pregnancy, obesity, and standing for long periods raise the risk of developing varicose veins. Elevating the legs above the level of the heart or putting on support hosiery before arising in the morning can relieve discomfort. In travenous injection of a substance that destroys veins (a sclerosing agent) or surgical removal of the affected veins may be necessary. ■

Artery Contraction

pressure that remains in the arteries before the next ventricular contraction is termed the diastolic pressure.

The surge of blood entering the arterial system during a ventricular contraction distends the elastic walls of the arteries, but the pressure begins to drop almost immediately as the contraction ends, and the arterial walls recoil. This alternate expanding and recoiling of the arterial wall can be felt as a pulse in an artery that runs close to the surface. Figure 15.34 shows several sites where a pulse can be detected. The radial artery, for example, courses near the surface at the wrist and is commonly used to sense a person's radial pulse.

The radial pulse rate is equal to the rate at which the left ventricle contracts, and for this reason, it can be used to determine heart rate. A pulse can also reveal something about blood pressure, because an elevated pressure produces a pulse that feels strong and full, whereas a low pressure produces a pulse that is weak and easily compressed. Clinical Application 15.4 describes how to measure arterial blood pressure.

O Distinguish between systolic and diastolic blood pressure.

^9 Which cardiac event causes systolic pressure? Diastolic pressure?

^9 What causes a pulse in an artery?

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