Circulatory System Overview

Lecture Focus

• Part 1: Structure of the circulatory system
• Part 2: Processes in the circulatory system (covered in next session)

Key Concepts

• Structure-Function Relationship: In biology, structure is linked to function.
• Types of Circulatory Systems:
  • Open Circulatory System: Found in small organisms, blood vessels are open-ended. Blood leaks out to tissues and re-enters the heart via open vessels.
    • Example: Insects (e.g., grasshoppers)
  • Closed Circulatory System: Blood is confined within vessels, more common in larger organisms.
    • Example: Humans, earthworms

Human Circulatory System

• Closed and Double Circulatory System
  • Blood circulates through the heart twice, reaching different destinations.

Types of Circulation

• Systemic Circulation: Blood to the body.
  • Oxygenated blood from lungs ➔ heart ➔ body
  • Blood collects CO2 ➔ becomes deoxygenated
• Pulmonary Circulation: Blood to the lungs.
  • Deoxygenated blood from body ➔ lungs for re-oxygenation

Heart Structure

• External Heart Components:

  • Superior Vena Cava: Large vein bringing blood from upper body
  • Right Atrium: Top chamber receiving blood
  • Coronary Arteries: Supply blood to heart
  • Right Ventricle: Muscular chamber pushing blood to lungs
  • Aorta: Largest artery, distributes oxygenated blood
  • Pulmonary Artery & Veins: Transport blood to and from lungs
  • Pericardium: Protective sac reducing friction

• Internal Heart Components:

  • Right Pulmonary Artery: Blood to right lung
  • Pulmonary Valve & Veins: Prevent backflow, bring blood from lungs
  • Tricuspid Valve: Between right atrium and ventricle
  • Left Atrium & Ventricle: Receive oxygenated blood from lungs, pump to body
  • Mitral Valve: Prevents backflow
  • Septum: Divides left/right heart, prevents mixing of blood

• Heart Wall Layers:

  • Pericardium: Outer protective layer
  • Epicardium, Myocardium, Endocardium: Inner layers, with myocardium being muscular

Blood Vessels

• Arteries: Thick, muscular, carry high-pressure blood away from heart
  • Narrow lumen
• Veins: Thinner walls, larger lumen, return blood to heart
  • Have valves to prevent backflow
• Capillaries: Microscopic vessels facilitating exchange between blood and tissues
  • One cell layer thick

Summary

• Closed System: Blood contained, no leaks
• Double Circulation: Blood circulates through heart to lungs & body
• Heart Chambers: Atria (upper), Ventricles (lower)
• Valves: Ensure one-directional blood flow
• Blood Vessels: Arteries (thick & muscular), Veins (larger lumen), Capillaries (thin for exchange)

Additional Notes

• Visual aids such as diagrams can be crucial for understanding anatomical structures.
• Understanding the differences in the blood vessel structure is key for grasping their functions.

End of Lecture Notes

Please watch the accompanying video for a visual representation of the circulatory system structures discussed.