Which Statement About Precapillary Sphincters Is CORRECT

question 142

Multiple Choice

Which statement about precapillary sphincters is CORRECT?

• A) They contract when oxygen levels in the tissue are low.
• B) They can close off the capillaries by contracting.
• C) They are openings that allow large molecules and blood cells to leave the capillary.
• D) When the precapillary sphincters are open, blood flows only through the thoroughfare channels.
• E) They are voluntary.

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Definitions:

Cardiac Cycle

refers to the sequence of events that occur in the heart during one beat, including the contraction (systole) and relaxation (diastole) periods.

Diastole

The phase of the heart cycle when the heart muscle relaxes and allows the chambers to fill with blood.

Ventricular Filling

The phase of the cardiac cycle in which the ventricles fill with blood, following diastole and before systole.

AV Valves

The atrioventricular valves, which include the mitral and tricuspid valves, control blood flow between the atria and ventricles in the heart.