BISC 132 - Recorded Lecture 5.1: Circulatory System & Introduction to the Immune System

Circulatory System Overview

• Previous Knowledge:
  • Reviewed open and closed circulatory systems in invertebrates and vertebrates.
  • Focus of this lecture: Closed circulatory systems.

Components of Blood

• Main Components:
  • Platelets: Small fragments, involved in clotting.
  • Blood Cells: Red blood cells (erythrocytes) and white blood cells (leukocytes).
  • Plasma: Liquid component of blood.

Plasma

• Mostly water, but contains:
  • Nutrients (e.g., glucose)
  • Wastes (e.g., urea)
  • Hormones
  • Ions (e.g., bicarbonate buffer)
  • Proteins (including clotting factors and fat carriers)
• Serum: Plasma without coagulation factors.

Red Blood Cells (RBCs)/Erythrocytes

• Disc-shaped, no nucleus.
• Contain hemoglobin, which carries oxygen (O2).

White Blood Cells (WBCs)/Leukocytes

• Part of the immune system.
• Will be discussed in detail in the immune system chapter.

Platelets

• Cell fragments, not complete cells.
• Involved in clotting along with proteins in plasma.

Blood Circulation Process

1. In Body and Head:
   • Blood loses O2 to tissues, becomes deoxygenated.
   • Convention: Deoxygenated blood is drawn as blue, but it's always red.
2. Blood to Heart:
   • Enters through veins (vein = vessel bringing blood to heart).
   • Moves into the right atrium (first chamber).
3. Movement in Heart:
   • Right atrium to right ventricle (valve ensures one-way flow).
4. To Lungs:
   • Deoxygenated blood moves via an artery (artery = vessel taking blood away from heart).
5. Reoxygenation in Lungs:
   • Blood picks up O2, becomes oxygenated (drawn red).
6. Back to Heart:
   • Enters left atrium from lungs.
7. Exit to Body:
   • Left atrium to left ventricle (one-way valve).
   • Blood pumped to head and body.
   • Cycle repeats.

Circulatory Circuits

• Pulmonary Circuit: Heart to lungs and back.
• Systemic Circuit: Heart to body and back.
• Coronary Circuit: Supplies blood to the heart muscle itself.

Vertebrate Circulatory Systems

• Mammals and Birds:
  • Four-chambered heart (double circulation).
• Reptiles:
  • Three-chambered heart, partial septum, some mixing of blood.
• Amphibians:
  • Three-chambered heart, no septum, more mixing of blood.
• Fish:
  • Two-chambered heart, single circulation.

Introduction to the Immune System

• Two Main Parts:
  • Innate immune system.
  • Adaptive immune system (covered later).

Innate Immune System

• Characteristics:
  • Limited specificity, very immediate.
  • Includes the skin as a physical barrier.

Skin

• Largest organ, acts as a barrier.
• Oils and sweat create inhospitable environment for pathogens.
• Normal flora crowd out pathogens.

Mucosal Epithelial Surfaces

• Protect entrances and exits of the body.
• Secrete mucus and enzymes to trap and destroy pathogens.

Leukocytes in Innate Immunity

• Pattern Recognition Receptors (PRRs):
  • Recognize pathogen-associated molecular patterns (PAMPs) on pathogens.
  • Leads to cytokine release and phagocytosis.

Inflammation

• Defined as localized redness, swelling, heat, and pain.
• Results from leukocyte movement to infection site and capillary leakage.

This concludes Lecture 5.1. The next lecture will continue with more on the immune system.