Hematopoiesis: -process of blood cell production
-Constant throughout life to replace RBCs that grow old and die, are killed by disease, or are
lost
... [Show More] through bleeding
-Occurs in liver and spleen of fetus
-Occurs in bone marrow after birth
-2 stages: 1. Proliferation (mitotic division)
2. Maturation (differentiation)
-Bone marrow: red (hematopoietic/active) & yellow (fatty/inactive)
Hematopoietic stem cells (HSCs)- all blood cells are created from HSCs
-signaled to undergo differentiation (by cytokines and chemokines, growth factors) to form
RBC, WBC, & platelets
• Lymphoid: T cell (T-lymphocyte) & B cell (B-lymphocyte)
• Myeloid: Monocyte & Granulocytes (WBCs)
• Erythrocyte (RBC)
• Megakaryocyte (Platelets)
Mesenchymal stem cells-develop into osteoclasts, fibroblasts, & adipocytes
Erythropoietin: -hormone that stimulates erythrocyte production
-Secreted by the kidneys in response to tissue hypoxia
Erythrocyte: -most abundant cells in the body
-primarily responsible for tissue oxygenation
-mature erythrocytes lack a nucleus and mitochondria, cannot synthesize protein or carry out
oxidative reactions. Cannot divide *anaerobic metabolism only
-life span: 100-120 days
-contains hemoglobin molecules
o Stages: (7-day process)
• Hemocytoblast (stem cell) binds with erythropoietin
• Proerythroblast- committed to morph into RBC
• Erythroblast- ribosome synthesis (2 phases)
• Normoblast- Hgb accumulation & nucleus ejection
• Reticulocyte –(immature RBC) released into circulation, no nucleus,
ribosome, or mitochondria
• RBC (after it has been in bone marrow 1-2 days)
Hemoglobin: oxygen carrying protein of the erythrocyte
-hemoglobin packed blood cells pick up oxygen in the lungs and exchange it for carbon
dioxide in the tissues
-composed of 2 pairs of polypeptide chains (globins) & 4 colorful iron complexes (hemes)
-can carry up to 4 molecules of oxygen
Oxyheoglobin- binding of oxygen to Fe in heme molecule, RED
Deoxyhemoglobin- reduced hemoglobin, after it releases the oxygen to the
tissues, BLUE [Show Less]