The Human Heart: An Extraordinary Machine

Heart Structure and Function

• Heart Chambers

  • 4 Chambers: Left atrium, Right atrium, Left ventricle, Right ventricle
  • Function: Contract in a rhythm known as the heartbeat

• Blood Flow

  • Blood from tissues and lungs flows into atria then ventricles
  • Interatrial and interventricular septum prevent mixing of blood between sides

Heart Valves

• Atria to Ventricles

  • Tricuspid Valve: Opens into right ventricle
  • Bicuspid (Mitral) Valve: Opens into left ventricle
  • Chordae Tendineae: Hold valves in place during contractions

• Ventricles to Arteries

  • Pulmonary Valve: Between right ventricle and pulmonary trunk
  • Aortic Valve: Connects left ventricle to aorta

Myocardium and Heart Contractions

• Myocardium: Heart muscle arranged in a unique pattern

  • 3 layers wrap around lower part of the heart
  • Twist and tighten to push blood

• Electrical Signals

  • Pacemaker Cells: Generate electrical signals
  • Myocytes: Contract as a group upon receiving signals

Dual Pump Function

• Right Side

  • Deoxygenated blood flows through superior and inferior vena cava into right atrium
  • Blood moves into right ventricle, contracts, sends blood to lungs

• Left Side

  • Oxygen-rich blood flows through pulmonary veins into left atrium
  • Blood moves into left ventricle, contracts, sends blood through aorta

Blood Supply

• Coronary Arteries: First branches off aorta supplying heart muscle
• Aorta Branching
  • Arteries diverge to head, arms, and rest of the body

Heart Rate and Blood Circulation

• Heart Rate

  • Average: 60-100 beats per minute

• Blood Circulation

  • Pumps about 5 quarts of blood per minute through arteries
  • Delivers oxygen and nutrients throughout the body