The Circulatory System

Circulatory System Overview

Functions of the Circulatory System

  • Transportation: Moves oxygen, glucose, carbon dioxide, nutrients, water, and waste products around the body.

  • Control: Regulates body temperature.

  • Protection: Contains cells and antibodies that fight infection and clotting agents to stop bleeding.

Double Circulatory System

  • Composed of two loops:

    • Pulmonary Circulation: Deoxygenated blood to lungs and oxygenated blood back to the heart.

    • Systemic Circulation: Oxygenated blood from the heart to the body and deoxygenated blood back to the heart.

Blood Vessels

  • Types:

    • Arteries: Carry blood away from the heart; thicker muscular walls; high pressure.

    • Veins: Carry blood back to the heart; thinner walls; have valves to prevent backflow.

    • Capillaries: Microscopic vessels where exchange of substances occurs; walls only one cell thick.

The Heart Structure

  • Contains four chambers:

    • Atria: Upper chambers (right and left atrium).

    • Ventricles: Lower chambers (right and left ventricle).

  • Valves: Prevent backflow of blood (e.g., tricuspid valve, bicuspid valve, semi-lunar valves).

Heart Function During Exercise

  • Heart rate: Increases to supply oxygen and nutrients faster.

  • Stroke volume: Volume of blood pumped per heartbeat increases.

  • Cardiac output: Total volume of blood pumped per minute increases with exercise.

Blood Pressure Factors

  • Depending factors:

    • Age, gender, stress, diet, and fitness level.

  • Effects of Exercise: Immediate increase in blood pressure; long-term regular exercise reduces blood pressure.

Temperature Regulation

  • Vasodilation: Capillaries widen to release heat when body temperature increases.

  • Vasoconstriction: Capillaries narrow to retain heat when body temperature decreases.

Blood Composition

  • Components:

    • Red Blood Cells: Transport oxygen; contain hemoglobin; bi-concave shape for increased surface area.

    • White Blood Cells: Defense against infection; some produce antibodies.

    • Platelets: Essential for blood clotting.

    • Plasma: Liquid component carrying cells, nutrients, waste, hormones.

Sports Performance and Blood

  • Higher red blood cell count is beneficial for oxygen transport during endurance activities.

  • Blood Doping: Illegal practice to enhance performance by artificially increasing red blood cell counts, which can lead to health risks.

Glossary of Terms

  • Stroke volume, cardiac output, blood pressure, vasodilation, vasoconstriction, red blood cells, white blood cells, platelets, plasma, blood doping, aorta, vena cava, pulmonary artery, pulmonary vein, pulmonary circulation, systemic circulation, oxygenated, deoxygenated, arteries, veins, capillaries, lumen, atria, ventricles, septum, tricuspid valve, bicuspid valve, semi-lunar valve, heart rate.