Understanding the Human Heart

Overview of the Heart

• The human heart beats about 100,000 times daily.
• Pumps around 2,000 gallons of blood through the body.
• Size: No bigger than a fist.
• Essential for circulating nutrients (food, water, oxygen) via 60,000 miles of blood vessels.

Blood Vessels

• Composed of three main types:
  • Arteries: Carry oxygenated blood away from the heart.
  • Veins: Carry deoxygenated blood back to the heart.
  • Capillaries: Small vessels where blood exchanges gases and nutrients with tissues.

Heart Structure

• The heart consists of four chambers:

  • Right Atrium
  • Left Atrium
  • Right Ventricle
  • Left Ventricle

• Contains four valves:

  • Tricuspid Valve
  • Mitral Valve
  • Aortic Valve
  • Pulmonic Valve
    (All valves are one-way valves to prevent backflow.)

How the Heart Works

1. Oxygenation: Blood becomes oxygen-rich in the lungs.
2. Oxygenated Blood Flow:
   • Carried to left atrium via pulmonary veins.
   • Left atrium relaxes and then contracts to push blood into the left ventricle through the one-way valve.
   • When the left ventricle contracts, blood is pumped into the aorta and distributed throughout the body (except lungs).
3. Deoxygenation:
   • Oxygen-rich blood reaches capillaries and becomes deoxygenated.
   • Deoxygenated blood returns via veins (formed from capillaries).
4. Returning to the Heart:
   • Deoxygenated blood enters the right atrium through the vena cava.
   • Right atrium contracts, sending blood to the right ventricle through a one-way valve.
   • Right ventricle then pumps blood into the pulmonary artery for re-oxygenation in the lungs.
5. Cycle Repeats:
   • Oxygenated blood returns to the heart through the pulmonary veins and the cycle starts anew.