Chapter 25 Blood Cells and the Hematopoietic System

Elements of the Hematopoietic System • All the blood cells and their precursors • The bone marrow, where blood cells have their origin • The lymphoid tissues where some blood cells circulate as they develop and mature Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Composition of Blood • Fluid/dissolved components – Water • Cellular elements – Red blood cells – Thrombocytes or platelets – Proteins – Small molecular substances – White blood cells • Lymphocytes • Leukocytes Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Figure 25. 1 Layering of blood components in an anticoagulated and centrifuged blood sample.

Question • All of the following are cellular components of blood except which one? – A. Macrophages – B. Mast cells – C. Neutrophils – D. Eosinophils Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Answer • B. Mast cells • Mast cells are not blood cells; rather they are found in connective tissue and initiate the inflammatory response. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Function of the Plasma Components of Blood • Carry the cells that transport gases

Plasma Proteins • Albumin – Comprises approximately 54% of the plasma proteins – Contributes to plasma osmotic pressure and the maintenance of blood volume – Serves as a carrier for certain substances Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Plasma Proteins (cont. ) • Globulins – Comprise approximately 38% of plasma proteins – 3 types: – Alpha globulins transport bilirubin and steroids – Beta globulins transport iron and copper. – Gamma globulins constitute the antibodies of the immune system. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Plasma Proteins (cont. ) • Fibrinogen – Makes up approximately 7% of the plasma proteins – Is converted to fibrin in the clotting process – The remaining 1% are hormones, enzymes, and carriers for lipids Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Blood Cells • Erythrocytes: red blood cells • Leukocytes: white blood cells • Thrombocytes:

Neutrophils • Constitute 50% to 60 % of white blood cells • Primarily responsible for maintaining normal host defenses against invading substances – First cells to arrive at the site of infection – Have their origins in the myeloblasts found in the bone marrow – Move to the tissue for approximately 1 to 3 days • Die in the tissue discharging phagocytic function or die of senescence Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Eosinophils • 1% to 3% of the total number of white blood cells • Increase in number during allergic reactions and parasitic infections – The agents associated with allergic reactions – In parasitic infections, the eosinophils use surface markers to attach themselves to the parasite and then release hydrolytic enzymes. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Basophils • 0. 3% to 0. 5% of the total leukocytes • Consist of heparin, an anticoagulant, histamine, a vasodilator, and other mediators of inflammation • Similar to mast cells • Involved in allergic and hypersensitivity reactions Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Lymphocytes • 20% to 30% of the total blood leukocytes • Function in the lymph nodes or spleen to defend against microorganisms through the immune response • Three types – B lymphocytes – T lymphocytes – Natural killer cells Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Monocytes and Macrophages • 3% to 8% of the total leukocyte count • Cells survive for months to years in the tissues. • Important role in chronic inflammation • Involved in the immune response – Activating lymphocytes – Presenting antigen to T cells Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Thrombocytes • Circulating cell fragments of the large megakaryocytes • Function to form the platelet plug to helps control bleeding • 8 to 9 days in circulation Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Figure 25. 7 Major maturational stages of blood cells. (CFU, colonyforming unit; NK, natural

Hematopoiesis • Blood cells originate from pluripotent stem cells in the bone marrow. • The proliferation, differentiation, and functional abilities of the various blood cells are controlled by cytokines. – Cytokines are hormone-like growth factors. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Hematopoietic Growth Factors • Increase peripheral stem cells for transplantation • Accelerate cell proliferation after bone marrow engraftment Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Useful Hematopoietic Growth Factors • Erythropoietin (EPO): stimulates RBC production • Thrombopoietin (TPO): stimulates the differentiation of platelets • Granulocyte colony-stimulating factor (G-CSF): promotes the proliferation neutrophils • Granulocyte-monocyte colony-stimulating factor (GMCSF): stimulates progenitors for granulocytes, monocytes, erythrocytes and megakaryocytes Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Conditions Responding to Use of Hematopoietic Growth Factors • Bone marrow failure caused by chemotherapy or aplastic anemia • Anemia of kidney failure • Hematopoietic neoplasms • Infectious diseases such as acquired immunodeficiency syndrome (AIDS) • Congenital and myeloproliferative disorders • Some solid tumors Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Question • Is the following statement true or false? • Hematopoietic growth factors are only associated with normal production of cells. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Answer • False • In disease states such as polycythemia vera, leukemia, and other blood cancers, inappropriate production of growth factors does occur. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

The Complete Blood Count • A complete blood count provides information regarding the number of blood cells and their structural and functional characteristics. • The white cell differential count is the determination of the relative proportions (percentages) of individual white cell types. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins

Diagnostic Tests • A complete blood count (CBC) is a commonly performed screening test that determines the number of red blood cells, white blood cells, and platelets per unit of blood. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins