Alterations in Hematologic Processes PDF

Alterations in Hematologic Processes Dr. Emily Larocque/Elizabeth Roe Components of the Hematologic System 91% water and 9% solutes 6 quarts (5.5 L) in adults Chief functions: Delivery of substances needed for cellular metabolism Removal of wastes Defense against microorganisms and injury Maintenanc...

Alterations in Hematologic Processes Dr. Emily Larocque/Elizabeth Roe Components of the Hematologic System 91% water and 9% solutes 6 quarts (5.5 L) in adults Chief functions: Delivery of substances needed for cellular metabolism Removal of wastes Defense against microorganisms and injury Maintenance of acid-base balance Components of the Hematologic System Plasma 50% to 55% of the blood volume Liquid portion that contains organic and inorganic elements Plasma proteins Albumin—function as carriers and control the plasma oncotic pressure Globulins—carrier proteins and immunoglobulins Clotting factors/proteins—promote coagulation, mainly fibrinogen Components of the Hematologic System Cellular components Erythrocytes and leukocytes Erythrocytes (red blood cells) Most abundant cells in blood Responsible for tissue oxygenation 100 to 120-day life cycle Components of the Hematologic System Leukocytes (white blood cells) Defend against infection and remove debris Act in the tissues but transported by circulation Classification by structure Granulocytes Agranulocytes Components of the Hematologic System Granulocytes Membrane-bound granules in their cytoplasm The granules contain enzymes capable of destroying microorganisms Inflammatory and immune functions Neutrophils Phagocytes in early inflammation Eosinophils Ingest antigen-antibody complexes Increase in parasitic infections Basophils Structurally and functionally similar to mast cells Components of the Hematologic System Agranulocytes Monocytes Reside in the blood and tissues to destroy germs and eliminate infected cells Lymphocytes Helps fight disease and infection Natural killer (NK) cells Control several types of tumors and microbial infections by limiting the spread and subsequent tissue damage Components of the Hematologic System Platelets (thrombocytes) Irregularly shaped cytoplasmic fragments Extremely small (only can be seen under a microscope) Essential for blood coagulation and control of bleeding Lymphoid Organs Spleen Largest lymphoid organ Fetal hematopoiesis, cleanses blood, initiates immune response, destroys aged cells, blood reservoir Splenic pulp Masses of lymphoid tissue Venous sinuses Phagocytosis of old, damaged, and dead blood cells Blood storage: 300ml Lymphoid Organs Lymph nodes Structurally part of the lymphatic system Functionally part of hematologic and immune systems Transport lymphatic fluid back to the circulation Cleanse the lymphatic fluid of microorganisms and foreign particles Erythropoiesis Process of red blood cell development Sequence In each step the quantity of hemoglobin increases and the nucleus decreases in size Regulation Causes an increase in red cell production in conditions of tissue hypoxia Erythropoiesis Old or senescent erythrocytes Increasingly fragile Normal destruction of senescent erythrocytes Aged red cells are sequestered and destroyed by macrophages. Primarily in the spleen In liver if spleen is dysfunctional or absent Oxygen-carrying protein of the erythrocyte Two pairs of polypeptide chains (globulins) Hemoglobin Most common in adults: two alpha and two beta chains Four colorful iron-protoporphyrin complexes (heme) Each heme carries one molecule of oxygen Heme bound to reduced ferrous iron (Fe2+) Hemoglobin Synthesis Nutritional requirements Building blocks: Proteins Amino acids Vitamins Vitamins B12, B6, B2, E, and C; folic acid; pantothenic acid; and niacin Minerals Iron and copper 14 Iron Cycle Iron Total body iron is bound to heme (in blood or muscle cells) or stored bound to ferritin or hemosiderin or in mononuclear phagocytes Less than 1 mg per day is lost in the urine, sweat, bile, and epithelial cells or from the skin and gut Iron cycle Iron produced by recycling iron from erythrocytes Controlled by hepcidin Iron Cycle Myelopoiesis Development of Leukocytes Development of granulocytes and monocytes Mature in the bone marrow Granulocytes become two pools Functional and circulating Stored in blood vessel walls: marginating storage pool Lymphopoiesis Development of lymphocytes Released into blood stream, mature in lymphoid organs Platelet levels are regulated by thrombopoietin Development of Platelets Platelets circulate for 10 days before losing their functional capacity Senescent platelets sequestered and destroyed in spleen 18 Arrest of bleeding by formation of blood clots Sequence of events: Hemostasis Vascular injury causes vasoconstriction Endothelial cell damage leads to platelet adherence and formation of a hemostatic plug Clotting system activated to form fibrin clots Fibrin/platelet clot contracts for form more permanent plug Hemostasis Function of clotting factors Intrinsic pathway Activated when factor XII (Hageman factor) contacts subendothelial substances exposed by vascular injury Extrinsic pathway Activated when tissue factor (TF) (tissue thromboplastin) is released by damaged endothelial cells Common pathway 20 Retraction and Lysis of Blood Clots Clot retraction Fibrin strands shorten; become denser and stronger to approximate the edges of the injured vessel and site of injury Facilitated by large numbers of platelets within the clot Lysis of blood clots Fibrinolytic system Plasminogen and plasmin Fibrin degradation products Fibrinolytic System Blood cell counts increase above adult levels at birth Pediatrics and Blood Trauma of birth and cutting the umbilical cord The hypoxic intrauterine environment stimulates erythropoietin production Results in polycythemia Newborns at risk for Pediatrics and Blood Impaired phagocytosis Bacterial infections Delayed wound healing Protection from disease provided by passive IgG antibody from mother Erythrocyte life span is normal but erythrocytes are replaced more slowly Aging and the Hematologic System Possible causes: Iron depletion Decreased total serum iron, iron-binding capacity, and intestinal iron absorption Lymphocyte function decreases with age The humoral immune system is less responsive 25 Alterations of Hematologic Function Common Diagnostic Tests Laboratory tests Prothrombin time – PT (clotting time – warfarin) Partial thromboplastin time - PTT (clotting time – heparin) International normalized ratio – INR (standardized clotting time) D-dimer (fibrinogen degradation product) CBC, red blood cell count, hemoglobin, hematocrit Platelet count 27 Anemia Reduction in the total number of erythrocytes in the circulating blood or in the quality or quantity of hemoglobin Impaired erythrocyte production Acute or chronic blood loss Increased erythrocyte destruction Combination of the above WHO criteria Men: Hb