3.3 Circulatory System

Main Parts of the Circulatory System

  1. Heart: Muscular organ that pumps blood.
  2. Blood: Fluid carrying oxygen, nutrients, and waste.
  3. Blood Vessels: Network of tubes (arteries, veins, capillaries) carrying blood.

Process of Circulation in the Body

  • Oxygenated blood leaves heart via arteries to body.
  • In capillaries, O₂/nutrients exchanged for CO₂/waste.
  • Deoxygenated blood returns to heart via veins.
  • Heart pumps deoxygenated blood to lungs (CO₂ released, O₂ picked up).
  • Newly oxygenated blood returns to heart, cycle repeats.

Components of Blood

  1. Plasma: Yellowish liquid; carries nutrients, hormones, waste.
  2. Blood Cells:
    • Red Blood Cells (RBCs) / Erythrocytes: Transport oxygen (via hemoglobin).
    • White Blood Cells (WBCs) / Leukocytes: Fight infections.
    • Platelets / Thrombocytes: Crucial for blood clotting.

Types of Blood Groups

  • Classified by antigens on RBC surface.
  • Four main ABO blood groups:
    • A
    • B
    • AB
    • O

Blood Pressure

  • Concept: Force exerted by circulating blood against artery walls.
  • Measured as systolic pressure (heart beats) over diastolic pressure (heart rests).

Heartbeat and Pulse

  • Heartbeat: Rhythmic contraction and relaxation of heart muscles (60-100 times/min).
  • Pulse: Throbbing sensation in arteries due to rhythmic heart contraction; corresponds to heartbeat.

Keeping the Heart Healthy

  • Through Exercise: Strengthens heart muscle, improves circulation, maintains healthy weight.
  • Through Good Food Habits: Balanced diet (fruits, vegetables, whole grains, lean proteins); limit saturated/trans fats, cholesterol, sodium, added sugars.