Hematopoiesis

Hematopoiesis Overview

• Hematopoiesis: The production and development of blood cells from hematopoietic stem cells.

• Blood Composition:

  • Average blood volume is 4-6 liters (4-5L in women, 5-6L in men).

  • Blood makes up approximately 8% of total body weight.

  • Normal pH range of blood: 7.35-7.45.

  • Blood consists of:

    • 55% plasma

    • 45% formed elements (red blood cells (44%), white blood cells, and platelets).

Plasma Composition

• Plasma is mainly composed of:

  • Water: 91.5%

  • Solutes: 8.5%

    • Proteins:

      • Albumin: 55% of proteins in plasma.

      • Globulins: 38%.

      • Fibrinogen: 7%.

    • Miscellaneous Solutes: Electrolytes, hormones, non-protein nitrogen compounds, and gases.

Blood Cellular Components

• Red Blood Cells (RBCs):

  • Typical reference ranges (per liter):

    • Male: 4.7-6.1 x10^12

    • Female: 4.2-5.4 x10^12

• White Blood Cells (WBCs):

  • Normal range: 4.0-11.0 x10^9.

• Platelets:

  • Normal range: 150-400 x10^9.

• Hemoglobin:

  • Male: 140-180 g/L

  • Female: 120-160 g/L.

Cell Morphology and Identification

• Erythrocyte Features:

  • Biconcave disc, average size of 7-8um.

  • Contains hemoglobin; no nucleus, uniform shape and size is critical for diagnosis.

• Platelets:

  • 1-4 um in size, average of 7-15 visible per oil immersion field.

• Leukocytes (WBCs):

  • Categories include: Neutrophils, Eosinophils, Basophils, Lymphocytes, and Monocytes.

Cell Types in Hematology

• Neutrophils:

  • Segmented (mature) and band (immature); critical for inflammation and immune response.

• Eosinophils:

  • Increase during allergic reactions and parasitic infections.

• Basophils:

  • Involved in allergic responses; release histamine.

• Lymphocytes:

  • Crucial for adaptive immune response (B cells and T cells).

• Monocytes:

  • Differentiate into macrophages in tissues; play roles in phagocytosis.

Hematopoiesis Mechanisms

• Hematopoietic Stem Cells:

  • Multiply and differentiate into various blood cells.

  • Response to growth factors (cytokines) for maturation and proliferation.

• Erythropoietin (EPO):

  • Produced by kidneys; stimulates RBC production in response to hypoxia.

  • EPO regulates RBC maturation from pronormoblast to erythrocytes.

Bone Marrow and Hematopoietic Sites

• Bone marrow primarily produces blood cells in adults, especially RBCs and platelets.

• Extramedullary Hematopoiesis: Occurs in liver and spleen under stress.

• Spleen Functions:

  • Functions in blood storage, filtration, and immune response.

Hematopoiesis: Developmental Stages

• Early embryonic hematopoiesis begins in the yolk sac, shifts to the liver, and later to the bone marrow.

• Production decreases after age 4; concentrated in axial skeleton and certain bones in adults.

Differentiation Processes

• Description of differentiation for specific cell lines:

  • Myelopoiesis for granulocytes and monocytes.

  • Lymphopoiesis for lymphocytes, involving T and B cell differentiation.

  • Megakaryocytopoiesis: Formation of platelets from megakaryocytes.

• Key identification features and roles of mature cell types emphasized.