The Heart and Cardiovascular System

Overview

• The heart is a muscular organ, about the size of a fist, located slightly left of center in the chest.
• It functions as a pump and is part of the cardiovascular system, along with blood vessels.
• The heart pumps around five quarts of blood per minute, beating approximately 100,000 times a day (35 million times a year).

Structure of the Heart

• Division: The heart is divided into right and left sides to prevent oxygen-rich blood from mixing with oxygen-poor blood.
  • Right Side: Comprises the right atrium and ventricle.
    • Collects oxygen-poor blood (blue) returning from the body.
    • Pumps blood to the lungs through the pulmonary arteries.
  • Left Side: Comprises the left atrium and ventricle.
    • Receives oxygen-rich blood (red) from the lungs.
    • Pumps it through the aorta to supply body tissues.

Blood Circulation

• Oxygen-poor blood returns to the heart after circulating through the body.
• In the lungs, blood is refreshed with oxygen, turning red.
• Valves: Four valves ensure blood flows in the correct direction:
  • Tricuspid, mitral, pulmonary, and aortic valves function like gates, opening only one way.

Heartbeat Cycle

• Systole: Contraction phase where ventricles contract, pushing blood into vessels.
  • Right ventricle contracts slightly before the left.
• Diastole: Relaxation phase where ventricles relax and fill with blood from the atria.

Coronary Circulation

• Heart is nourished by blood through coronary arteries.
  • These vessels branch into capillaries on the heart surface.

Electrical System

• The heart has electrical pathways that control the heartbeat.
  • Impulses start in the right atrium and travel to the ventricles.
  • Ensures the heart beats in a coordinated rhythm, maintaining blood circulation.

Importance

• The continuous exchange and circulation of oxygen-rich and oxygen-poor blood are vital for sustaining life.