Cardiovascular System Overview

Introduction

• The cardiovascular system in mammals, such as humans, includes the heart and blood vessels.
• It functions as a closed double circulatory system, with blood passing through the heart twice per body circuit.

Circulatory System

• Pulmonary Circulation: Transports blood to the lungs for oxygenation and CO2 removal.
• Systemic Circulation: Delivers oxygenated blood throughout the body.

Blood Vessels

Types

• Arteries: Carry blood away from the heart; high pressure; mostly oxygenated blood.

  • Composed of three layers: Tunica externa (collagen), Tunica media (smooth muscle & elastic fibers), and Tunica intima (endothelium).
  • Pulmonary artery is an exception (carries deoxygenated blood).

• Capillaries: Sites of material exchange; thin walls (one cell thick); form capillary beds.

  • Allow passage of oxygen, CO2, and nutrients.
  • Fenestrated capillaries have pores for small molecules.

• Veins: Return deoxygenated blood to the heart at low pressure.

  • Wider lumen; contain valves to prevent backflow.
  • Pulmonary vein is an exception (carries oxygenated blood).

The Heart

• Four chambers: two atria and two ventricles.
• Left side pumps oxygenated blood; right side pumps deoxygenated blood.
• Valves: Atrioventricular (between atria and ventricles) and Semilunar (in pulmonary artery and aorta).

Cardiac Cycle

• Atrial & Ventricular Diastole: Blood flows into ventricles from atria.
• Atrial Systole: Atria contract, pushing blood into ventricles.
• Ventricular Systole: Ventricles contract, pushing blood out to body/lungs.

Heart Rate and Exercise

• Heart rate increases to meet energy demands during exercise.
• Chemoreceptors detect CO2 levels and trigger responses to adjust heart rate.
• Baroreceptors monitor blood pressure.

Tissue Fluid and Exchange

• Formed at capillary arterial end due to high hydrostatic pressure.
• Allows exchange of solutes like oxygen and glucose with tissues.
• Osmotic pressure returns most fluid back to capillaries; remainder taken by lymphatic system.

Lymphatic System

• Collects excess tissue fluid as lymph.
• Lymph nodes filter lymph, containing macrophages and lymphocytes.

Comparison: Blood Plasma vs Tissue Fluid

• Plasma: Contains proteins, more nutrients, and red & white blood cells.
• Tissue Fluid: Fewer proteins, fewer nutrients, some white blood cells, no red blood cells.

Summary

• The key concepts covered offer a foundational understanding useful for exam revision.
• Review structure, function, and interactions of the cardiovascular system components.