Structure of the Heart (Leaving Cert Biology): Revision Notes

Structure of the Heart

• The heart is located between the lungs and above the diaphragm.
• The heart is made of cardiac muscle, which never tyres. It is under involuntary control.
• It is surrounded by a membrane called the pericardium. This reduces friction between the heart and nearby organs.

• Chambers:
  • Two upper chambers: Atria
  • Two lower chambers: Ventricles
• Ventricles:
  • The right ventricle pumps blood to the lungs.
  • The left ventricle is thicker because it pumps blood all around the body.
• The heart is separated into left and right sides by a wall called the septum.

• Valves:
  • The atria and ventricles are separated by valves, which prevent the backflow of blood.
  • The tricuspid valve is between the right atrium and right ventricle.
  • The bicuspid valve is between the left atrium and left ventricle.
  • There are two semilunar valves.
  • One where the aorta leaves the left ventricle and another where the pulmonary artery leaves the right ventricle.

• Key Blood Vessels:
  • Aorta: Largest artery, carries oxygenated blood from the left ventricle to the body.
  • Vena cava: Largest vein, carries deoxygenated blood from the body to the heart.
  • Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs.
  • Pulmonary vein: Brings oxygenated blood from the lungs to the heart.