Lecture on Hematopoiesis and Erythropoiesis

Hematopoiesis

• Definition: The process of making blood.
• Involves the production of:
  • Red Blood Cells (RBCs)
  • White Blood Cells (WBCs)
  • Platelets

Erythropoiesis

• Focus: Production of red blood cells (erythrocytes).
• Stimulus: Erythropoietin hormone.
• Source: Kidney releases erythropoietin in response to low oxygen (hypoxia).
• Conditions Causing Hypoxia:
  • Respiratory issues (e.g., cold, pneumonia, bronchitis)
  • High altitudes (e.g., traveling to mountains)
  • Increased physical activity
  • Blood loss or spleen/liver destroying too many RBCs
• Effects of Erythropoietin:
  • Increases RBC production.
  • Excessive RBCs can lead to increased blood viscosity, potential stroke, or heart attack.

Red Blood Cell Lifecycle

• Source: Bone marrow, originating from common stem cells.
• Types of Stem Cells:
  • Fetal stem cells: Can become any cell type.
  • Adult stem cells: Limited to blood cells.
• Production Pathway:
  1. Pluripotent Stem Cell
  2. Colony Forming Unit
  3. Erythroblast
  4. Reticulocyte
  5. Mature Erythrocyte
• Note: Erythroblast stage involves hemoglobin production.

Hemoglobin

• Structure: Complex protein with quaternary structure.
• Components:
  • Protein strands
  • Iron (Fe) atom
• Function:
  • Carries oxygen and carbon dioxide.
  • Bound states: Oxyhemoglobin, Carbaminohemoglobin, Carboxyhemoglobin

Recycling of Hemoglobin

• Primary Site: Spleen (also liver as backup)
• Breakdown Products:
  • Heme: Iron (recycled) and Bilirubin
  • Globin: Amino acids (recycled)
• Bilirubin Pathway:
  • Converted to bile in the liver.
  • Accumulation leads to jaundice.

Nutritional Requirements for RBCs

• Essential Nutrients:
  • Amino acids
  • Iron
  • Folic acid
  • Vitamin B12

Function and Importance of RBCs

• Main Functions:
  • Oxygen transport
  • Carbon dioxide removal
  • pH balance
• Lifespan: Approx. 120 days

Spleen

• Roles:
  • Breaks down old RBCs, WBCs, and platelets.
  • Stores blood for emergencies.
  • Removes debris and foreign material.
• Fetal Function: Produces RBCs before bone marrow is fully developed.
• Note: Non-essential organ, but plays a significant role in blood maintenance.