Hematopoiesis and Erythropoiesis

Hemato-Lymphoid System (HLS)

• Hematopoiesis is the formation of blood cellular components, and all types of blood cells are derived from pluripotent primitive cells (stem cells).
• In adults, hematopoiesis mainly occurs in the bone marrow, but it can also occur outside the bone marrow (spleen and liver) in certain diseases, known as extramedullary hematopoiesis.

Erythropoiesis

• Erythropoiesis is the process that produces red blood cells (erythrocytes), developing from erythropoietic stem cells to mature red blood cells.
• The term "erythropoiesis" comes from Greek, with "erythro" meaning "red" and "poiesis" meaning "to make".

Red Blood Cells (RBCs)

• Each mature RBC contains around 270 million hemoglobin molecules.
• Hemoglobin is a tetramer composed of two parts: Globin (4 protein chains, 2α and 2β subunits) and Heme (porphyrin ring with central iron).
• 4 heme groups are attached to each globin chain, forming hemoglobin (HEMOGLOBIN = HEME + GLOBIN).

Life Cycle of RBCs and Anemia

• Anemia is a reduction in the oxygen-transporting capacity of blood, resulting from a decrease in total circulating RBC mass below normal levels.
• Anemia can result from:
  • Excessive bleeding
  • Increased RBC destruction
  • Decreased RBC production
• Definition of anemia:
  • In males: Hb < 13.5 g/dL
  • (Note: further definition for females is not provided in the text)

Hemato-Lymphoid System (HLS)

• Hematopoiesis is the formation of blood cellular components, and all types of blood cells are derived from pluripotent primitive cells (stem cells).
• In adults, hematopoiesis mainly occurs in the bone marrow, but it can also occur outside the bone marrow (spleen and liver) in certain diseases, known as extramedullary hematopoiesis.

Erythropoiesis

• Erythropoiesis is the process that produces red blood cells (erythrocytes), developing from erythropoietic stem cells to mature red blood cells.
• The term "erythropoiesis" comes from Greek, with "erythro" meaning "red" and "poiesis" meaning "to make".

Red Blood Cells (RBCs)

• Each mature RBC contains around 270 million hemoglobin molecules.
• Hemoglobin is a tetramer composed of two parts: Globin (4 protein chains, 2α and 2β subunits) and Heme (porphyrin ring with central iron).
• 4 heme groups are attached to each globin chain, forming hemoglobin (HEMOGLOBIN = HEME + GLOBIN).

Life Cycle of RBCs and Anemia

• Anemia is a reduction in the oxygen-transporting capacity of blood, resulting from a decrease in total circulating RBC mass below normal levels.
• Anemia can result from:
  • Excessive bleeding
  • Increased RBC destruction
  • Decreased RBC production
• Definition of anemia:
  • In males: Hb < 13.5 g/dL
  • (Note: further definition for females is not provided in the text)

Learn about the formation of blood cellular components, including erythropoiesis, and how hematopoiesis occurs in the bone marrow and other organs in certain diseases.