The Heart (SQA National 5 Biology): Revision Note

The structure & function of the heart

• The heart has four internal chambers separated into two halves:

  • The right side of the heart pumps blood to the lungs for gas exchange

  • The left side of the heart pumps blood under high pressure to the body

• The four chambers of the heart are divided into top and bottom:

  • Chambers at the top are the atria

  • Chambers at the bottom are the ventricles

  • Valves separate the two chambers on each side

The pathway of blood through the heart

• Blood is pumped towards the heart in veins

  • Deoxygenated blood from the body enters the right atrium through the vena cava

  • Oxygenated blood from the lungs enters the left atrium through the pulmonary vein

• Blood is pumped away from the heart in arteries

  • The right atrium pumps blood through a valve into the right ventricle, which sends it to the lungs via the pulmonary artery

    • In the lungs, oxygen diffuses in from the alveoli and carbon dioxide diffuses out

  • The left atrium pumps blood through a valve into the left ventricle, which pumps it through the aorta to the rest of the body

    • The left ventricle has a thicker muscle wall because it needs to pump blood at a higher pressure around the whole body

• The coronary arteries on the outside of the heart deliver oxygenated blood to the heart muscle itself, allowing it to carry out respiration