The Circulatory System

Overview

• The circulatory system is an organ system responsible for transporting oxygen and nutrients to body tissues.
• It consists of:
  • Blood: Carries oxygen and nutrients.
  • Blood Vessels: Hold the blood.
  • Heart: Pumps the blood.

Double Circulatory System

• The system has two loops:
  1. Pulmonary Circuit: Carries deoxygenated blood from the heart to the lungs and back.
  2. Systemic Circuit: Carries oxygenated blood from the heart to the body and back.

Structure and Function of the Heart

• The heart contains four chambers with thick muscular walls:
  • Atria (top chambers): Singular is atrium.
  • Ventricles (bottom chambers).
• Valves between chambers and vessels prevent backflow.

Blood Flow Through the Heart

1. Blood enters via the vena cava (deoxygenated) and pulmonary vein (oxygenated).
2. Blood flows into the right atrium and left atrium.
3. Atria contract, moving blood to ventricles.
4. Ventricles contract, pushing blood into the pulmonary artery (to lungs) and aorta (to body).
5. Cycle repeats ~70 times per minute, >100,000 times daily.

Pacemaker Cells

• Located in the right atrium, these cells regulate heartbeats via electrical impulses.
• Artificial pacemakers can be implanted if the natural pacemaker cells malfunction.

Arteries vs. Veins

• Arteries: Vessels carrying blood away from the heart.
  • Not always oxygenated (e.g., pulmonary artery).
• Veins: Vessels carrying blood to the heart.
  • Not always deoxygenated (e.g., pulmonary vein).

Coronary Arteries

• Small arteries branching from the aorta.
• Supply the heart muscle with oxygenated blood and nutrients.

Conclusion

• Understanding the heart's structure and function is key to grasping the circulatory system's role.
• Important distinctions between arteries and veins to avoid misconceptions.

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