Immune System and Erythroid Lineage Notes

  • Introduction to Formed Elements

    • The immune system involves microscopic anatomy and physiology, which will be covered in depth in future chapters, specifically after the first exam when discussing lymph and the immune system.

    • Today's discussion on formed elements of blood (e.g., leukocytes) will be an abbreviated description, acknowledging that more detail will follow.

    • The upcoming midterm exam one (week four) will not cover the entire immune system chapter.

  • Hematopoiesis: Formation of Formed Elements

    • Location: Red bone marrow, known as hematopoietic tissue.

    • Process: Hematopoiesis is the verb describing the accelerated rate of formation of these elements.

    • Rate: The body constantly produces and destroys formed elements (e.g., 3,000,0003,000,000 red blood cells are made in a second), necessitating continuous refreshment due to their limited lifespan (half-life).

    • Principle: Form confers function – the structure, location, and functional tissue (parenchyma) of organs determine their capabilities.

    • Organ Structure: Organs consist of:

      • Stroma: Typically a connective tissue scaffolding or skeleton providing shape (e.g., ear shape).

        • (Example: VMed research involves 3D3D printing organic hydrocarbon stromas for organ banks, laying down parenchyma with stem cells which commit to the environment. This research explores growing backup organs like hearts).

      • Parenchyma: The functional tissue of the organ.

  • Red Blood Cells (Erythrocytes)

    • Formation Process: Erythropoiesis (eryth = red, cyte = mature cell).

    • Misnomer: A mature erythrocyte is not a true cell because it lacks a nucleus and other key organelles.

    • Last True Form: Before ejecting its nucleus, the erythrocyte was a true cell.

    • Internal Environment: Primarily cytoskeleton and a high concentration of hemoglobin.

    • Organelle Deficiency: Once mature, it lacks:

      • Nucleus: Ejected, meaning it cannot repair or divide.

      • Mitochondria: Cannot perform aerobic respiration or oxidative phosphorylation for ATP production.

      • Ribosomes: Cannot synthesize new enzymes or proteins after its initial days of circulation.

    • Lifespan: Circulates for about 120120 days (4 months).

    • Primary Functions:

      • Oxygen and Carbon Dioxide Transport: Acts as an