Lecture 5.1: Circulatory and Immune Systems

Circulatory System Overview

• Focus: Closed circulatory systems
• Components of Blood:
  • Plasma: Liquid component minus cells
    • Mostly water, containing nutrients (e.g., glucose), wastes (e.g., urea), hormones, ions, proteins (e.g., clotting factors)
    • Serum: Plasma without coagulation factors
  • Blood Cells:
    • Red Blood Cells (Erythrocytes): Disc-shaped, no nucleus, carry hemoglobin for O2 transport
    • White Blood Cells (Leukocytes): Involved in immune response (details in immune system chapter)
  • Platelets: Small cell fragments, involved in clotting

Blood Circulation

1. Deoxygenated Blood Flow:
   • Blood loses O2 in the body and head
   • Enters heart through veins into the right atrium
   • Moves to the right ventricle, pumped to lungs through arteries
2. Oxygenated Blood Flow:
   • Blood picks up O2 in the lungs
   • Enters the heart through left atrium
   • Moves to left ventricle, then pumped to body and head
3. Circulatory Circuits:
   • Pulmonary Circuit: Heart to lungs and back
   • Systemic Circuit: Heart to body/head and back
   • Coronary Circuit: Supplies blood to the heart muscle

Comparison of Vertebrate Circulatory Systems

• Mammals/Birds: 4-chambered heart, double circulation, no mixing of blood
• Reptiles: 3-chambered heart, partial septum, some mixing
• Amphibians: 3-chambered heart, no septum, significant mixing
• Fish: 2-chambered heart, single circulation

Introduction to the Immune System

• Divisions: Innate and Adaptive Immune Systems
  • Innate Immune System
    • Limited pathogen specificity, immediate response

Physical Barriers

• Skin: Largest organ, provides a barrier with low pH, oils, and normal flora
• Mucosal Epithelial Surfaces: Found at body entrances/exits, secretes mucus and enzymes (e.g., lysozyme)

Cellular Components

• Leukocytes and Pathogen Recognition
  • PRRs (Pattern Recognition Receptors) on leukocytes bind to PAMPs (Pathogen-Associated Molecular Patterns)
  • Cytokines: Signaling molecules released upon recognition, lead to phagocytosis
• Inflammation: Redness, swelling, heat, and pain from leukocyte movement to injury site

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This concludes Lecture 5.1. Further details on the immune system will be covered in the next lecture.