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TRANSPORT IN PLANTS AND ANIMALS
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EXCRETION AND HOMEOSTASIS
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Biology Form 2
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Systole (Contraction)

When the ventricular muscles contract, the atrioventricular (cuspid) valves close preventing the backflow of blood into the auricles.

The volume of the ventricles decreases while pressure increases, to force blood out of the heart to the:

  • Lungs via the semilunar valve through the pulmonary artery.
  • Body tissues except the lungs via the semilunar valve through the aorta.

The thick cardiac muscles of the left ventricle generate high pressure which forces the blood to the furthest tissue.

A systole is always followed by a diastole and the two make a complete heartbeat.

The heart contracts at an average rate of 60 to 70 times per minute.

The rate of heartbeat can be increased by emotions, high temperature and age.

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