BISC 132 - Lecture 5.1: Circulatory System and Introduction to Immune System

Circulatory System Overview

• Previous Knowledge: Covered open vs. closed circulatory systems in earlier lectures.
• Focus: Closed circulatory systems.

Blood Components

• Blood Composition:
  • Whole blood = Plasma + Blood Cells + Platelets
• Plasma:
  • Liquid component of blood, mostly water.
  • Contains nutrients (e.g., glucose), wastes (e.g., urea), hormones, ions, proteins, and clotting factors.
  • Serum: Plasma without coagulation factors.

Blood Cells

• Red Blood Cells (RBCs/Erythrocytes):
  • Disc-shaped, no nucleus.
  • Contain hemoglobin for O2 transport.
• White Blood Cells (WBCs/Leukocytes):
  • Involved in the immune system (details in future lectures).

Platelets

• Description: Cell fragments involved in clotting.
• Function: Work with plasma proteins to form clots and prevent blood leakage.

Blood Circulation

• Basic Process:
  • Starts in body/head: Blood loses O2 → deoxygenated (drawn blue in diagrams).
  • Veins: Bring deoxygenated blood back to the heart (right atrium → right ventricle).
  • Arteries: Carry blood away from heart.
  • Blood moves to lungs to pick up O2 → oxygenated (drawn red in diagrams).
  • Oxygenated blood returns to heart (left atrium → left ventricle) → goes to body/head.
• Heart Chambers:
  • Blood enters: Atria
  • Blood exits: Ventricles
  • Right side: Deoxygenated
  • Left side: Oxygenated

Circuits

• Pulmonary Circuit: Heart ↔ Lungs
• Systemic Circuit: Heart ↔ Body
• Coronary Circuit: Supplies heart muscle with blood.

Vertebrate Circulatory Systems

• Mammals/Birds:
  • Four-chambered heart, double circulation.
  • Complete separation of oxygenated/deoxygenated blood.
• Reptiles:
  • Three-chambered heart, partial septum, some mixing.
• Amphibians:
  • Three-chambered heart, no septum, more mixing.
• Fish:
  • Two-chambered heart, single circuit.

Introduction to the Immune System

Innate Immune System

• Characteristics:
  • Limited specificity, immediate response.
  • Involves skin and mucosal surfaces.

Skin

• Largest organ, acts as a barrier.
• Features:
  • Low pH and normal flora create inhospitable environment for pathogens.
  • Prevents pathogen entry.

Mucosal Epithelial Surfaces

• Found at entrances/exits of the body.
• Secrete mucus and enzymes to trap/destroy pathogens.

Leukocytes and Innate Immunity

• Pattern Recognition:
  • Leukocytes (e.g., macrophages) use pattern recognition receptors (PRRs).
  • Recognize pathogen-associated molecular patterns (PAMPs) like lipopolysaccharides.
  • Triggers cytokine release and phagocytosis.
• Inflammation:
  • Cytokines bring leukocytes to injury site.
  • Results in redness, swelling, heat, and pain.

Next Steps

• Further details on the immune system, including the adaptive immune system, will be covered in subsequent lectures.