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Chapter 14: Disorders of Red Blood Cells

Terms in this set (55)

Red Blood Cells
carriers of CO2 and transports to tissues as well as participates in acid-base balance, most common type of blood cell, biconcave shape of the red blood cell and the flexibility is maintained by a network of proteins especially one called spectrin. Spectrin attaches to anakryrin which is anchored to an integral protein that spans the membrane thus causing elasticity and the biconcave shape
Hemoglobin
has four polypeptide chains that consists of a globin and heme unit which surrounds an atom of iron that binds oxygen, thus a molecule, which has four ploypeptide chains can carry four oxygen molecules,
Adult (HbA)
consists of a pair of alpha chains and a pair of beta chains
Fetal (HbF)
the predominant hemoglobin in fetus from 3-9 months of gestation, has a higher affinity than HbA, replaced by HbA within 6 months of birth
Hemoglobin Synthesis
the rate at which hemoglobin is synthesized depends on the availability of iron for heme synthesis, lack of iron results in low hemoglobin in RBC and return to the circulation and returned to the bone marrow for incorporation into new RBC or to the liver and other tissues for storage (recycling), when there is iron overload, excretion of iron is acceleration, iron is either excreted through feces or stored in tissues. Ex: iron is stored in the liver as ferritin, protein-iron complex which can return to the circulation of iron levels are low
Red Cell Production
also known as erythropoiesis, until 5 years of age almost all bones produce red cells to meet growth needs of a child, bone marrow gradually declines after 5 years of age and after 20 years of age, red bone marrow starts getting replaced with fatty yellow bone marrow causing a reduced red blood cell production, RBC's are deprived from their precursor cells: erythroblasts, erythroblasts become normoblasts which then become reticulocytes then become erythrocytes, from normoblast to reticulocyte, the red blood cells gains hemoglobin and loses its nucleus, regulated by the body's oxygen needs
Red Cell Destruction
cell avg. lifespan is 120 days, when it gets old, phagocytes go to phagocytosis because their old and defective, when the phagocytes ingest it, the amino acids are gonna be reused, the heme is being converted to bilirubin
Red Cell Metabolism and Hemoglobin Oxidation
relies on glucose and glycolytic pathway for its metabolic needs, red blood cells lacks mitochondria, deficiency of the glycolytic enzymes leads to the premature death of the RBC. 2,3 diphosphglyerate can bind to hemoglobin which changes its conformation and loses its affinity for oxygen, increase in 2,3-DPG occurs in conditions of chronic hypoxia such as chronic lung disease, anemia, and residence at high altitudes, oxidations of hemoglobin can be interrupted by certain chemicals (nitrates and sulfates) and drugs that oxidize hemoglobin to an inactive form
Lab Tests for RBC
can be studied by taking sample of blood
Red Blood Cell Count
total number of RBC in microliter (uL) of blood
Percentage of Reticulocytes
provides an index rate of red cell production
Hemoglobin Per Deciliter
measures hemoglobin concentration in blood
Hemocrit
measures the red cell mass in 100-mL plasma volume, can be deceptive because because it varies with quantity of extracellular fluid, extracellular fluid can rise with dehydration and fall with over-expansion of extracellular fluid volume
Mean Corpuscular Volume (MCV)
size and volume of the RBC's, falls in microcytic (small cell) anemia and rises in macrocytic (large cell) anemia
Mean Corpuscular Hemoglobin Concentration
concentration of hemoglobin in each cell, measured by the color of RBC, normochromic: normal color. hypochromic: decreased color. hyperchromic: increased color
Mean Cell Hemoglobin
refers to the mass of the red cell, is less useful in classifying anemias
Anemia
abnormally low number of circulating red blood cells or levels of hemoglobin, or both resulting in diminished oxygen-carrying capacity, results from excessive loss (bleeding) or destruction (hemolysis) of RBC or from deficient RBC production because of lack of nutrition or bone marrow failure. Manifestation of impaired oxygen transport and resulting compensatory mechanisms, reduction in red cells indices and hemoglobin levels, signs and symptoms associated with the pathologic process that is causing the anemia, the manifestation of anemia depends on its severity, the rapidity of its development and the persons age and health status
Blood Loss Anemia
the clinical and red cell manifestation depend on the rate of the hemorrhage and whether the bleeding loss is external or internal, acute blood loss usually results from internal blood loss, fall in RBC count, hemocrit, and hemoglobin is caused by hemodilution, external bleeding can cause iron loss and possible iron deficiency, rapid blood loss can cause circulatory shock and circulatory collapse, slow blood loss the amount of the red cell mass lost can reach 50% without any signs or symptoms occuring
Hemolytic Anemias
Characterized by the premature destruction of RBC, the retention in the body of iron and the other products of hemoglobin destruction, and an increase in erythropoiesis, red cells can breakdown within or outside the vascular compartment
Intravascular Hemolysis
less common, occurs as a result of complement fixation in transfusion reactions, mechanical injury, or toxic factors, characterized by hemoglobinemia, hemoglobinuria, jaundice and hemoiderinuria
Extravascular Hemolysis
when red cells become less deformable, making it difficult for them to transverse the splenic sinusoids (small capillary that connects to the spleen) the abnormal red cells are phagocytized by macrophages in the spleen, can also be based on whether the cause is intrinsic or extrinsic
Intrinsic Causes
defects of the red blood cell membrane, the various hemoglobinopathies, and inherited enzyme defects, the abnormal substitution of the amino acids in the hemoglobin molecule (ex: sickle cell disease) the defective synthesis of one of the polypeptide chains that form the globin portion of hemoglobin (ex: thalassemias)
Extrinsic Causes
caused by agents external to the RBC such as drugs bacterial and other toxins, antibodies, and physical trauma, they all cause premature and accelerated destruction of blood cells, they cannot all be treated the same way
Spherocytosis
transmitted by autosomal dominant and is the most common disorder of the cell membrane, caused by abnormalities of spectrin and and ankyrin membrane proteins that give RBC its biconcave shape, causes the RBC to become sphere shaped therefore making susceptible to destruction in the sinuses of the splenic circulation, clinical signs include mild hemolytic anemia, jaundice, splenomegaly, and bilirubin gallstones
Sickle Cell Diease
disease where abnormal hemoglobin (HbS) leads to chronic hemolytic anemia, pain and organ failure, transmitted by the recessive inheritance and can manifest as sickle cell trait (heterozygote with one HbS gene) or sickle cell disease (homozygote with two Hbs genes), results from mutation in the beta chain of the hemoglobin molecule, the substitution of glutamic acid (codes for HbA) by valene (codes for abnormal HbS) presence of HbS in hemoglobin causes RBC to become deoxygenated causing it to become sickled, chronic hemolytic anemia, blood vessel occulation, factors associated: cold, stress, physical exertion, infection, and illness that hypoxia, dehydration, or acidosis
Clinical Course
stroke, retal infracts: blindness, lung infracts: Pneumonia/ acute chest syndrome, iron overload in the heart and liver, atrophic spleen, pigment gallstones, kidney infracts: chronic kidney disease, avascular necrosis of femoral head, painful infracts: bones of fingers and toes, osteomyelitis, skin ulcers
Diagnosis and Screening
Neonatal diagnosis of sickle cell disease is made on the basis of clinical finding and hemoglobin solubility results, which is confirmed by hemoglobin electrophoresis. Prenatal diagnosis is done by analysis of fetal DNA obtained by aminocentesis
Management
currently no known cure for sickle cell disease, ways to decrease rate of sickling of red blood cells include taking a drug called hydroxyurea which synthesizes more HbF and less HbS which is the hemoglobin that leads to sickle cell disease
The Thalassemias
inherited disorder in which there is a decreased synthesis of either the alpha or beta globin chains of HbA by deficient synthesis of the alpha beta chain, low intracellular hemoglobin (hypochromia) due to decreased of the affected chain, continued production of the unaffected chain
Beta Thalassemias
also known as Cooley anemia or mediterranean anemia, most commonly affects Mediterranean populations of southern italy and greece, both are common in Africa and African Americans, it causes defects in beta chain synthesis which causes an excess of alpha chain synthesis, excess alpha chains are then denatured to form precipitates called Heinz bodies, these precipitates can impair DNA synthesis and cause damage to the red cell membrane, iron overload can be a major complication
Alpha Thalassemias
most common in asians, both common in african and african american, caused by a gene deletion that results in defective chain synthesis, alpha globin chains of hemoglobin is controlled by two pairs or four genes, severity of the disorder depends on number of gene deletions
One Gene (alpha thal)
they are silent carriers and are asymptomatic (a carrier but no symptoms of the disorder)
Two Genes (alpha thal)
they have the alpha thalassemias trait and can exhibit mild hemolytic anemia
Three Genes (alpha thal)
leads to unstable aggregates of alpha chains called hemoglobin H (HbH)
Four Genes (alpha thal)
the most severe form of alpha thalassemia, occurs in infants, a hemoglobin called Hb Bart is formed exclusively for HbF which is found only in fetuses, which is why it occurs only infants, usually results in death in utero
Inherited Enzyme Defects
results in hemolytic anemia comes from a deficiency of G6PD, the gene that determines this enzyme is found on the X chromosome, the defect is only expressed in males and homozygous females, makes red cells more vulnerable to oxidants and causes direct oxidation and hemoglobin to methomoglobin, which cannot transport oxygen and denaturing of the hemoglobin molecule to form Heinz Bodies which are precipitated in the RBC, hemolysis occurs as damaged RBC move thru the narrow vessels of the spleen causing hemoglobinemia, hemoglobinuria and jaundice
Acquired Hemolytic Anemias
several exogenous factors that can lead to the destruction or hemolysis of red blood cells by direct membrane destruction or by antibody mediated lysis
Direct Membrane Destruction
various drugs, chemicals, toxins, venoms, and infections such as malaria destroy red cell membrane directly, can also be destroyed by mechanical factors such as prosthetic heart valves, vasculitism, and severe heart burns
Warm-Reacting Antibodies of the IgG Type
maximally active at 37 degrees Celsius, accounts for 80% if cases of hemolytic anemia, causes no morphologic or metabolical alteration in the red cell, they react with antigens on the red cell membrane causing destructive changes that lead to spherocytosis. Ends up in phagocytic destruction in the spleen reticuloendothelial system
Cold-Reacting Antibodies of the IgM Type
activate complement, chronic hemolytic anemia occurs with lymphorproliferative disorders and as an idiopathic (spontaneous) disorder of unknown cause: results in vascular obstruction by red blood cells resulting in pallor (pale skin), cyanosis of the parts exposed to cold temperatures, Raynaud phenomenon, develops in only few persons and is not severe
Anemias of Deficient of Red Cell Production
decreased production of RBC in the bone marrow may result in anemia, deficiency of nutrients for hemoglobin synthesis or DNA synthesis may reduce RBC reduction in the red bone marrow
Iron-Deficiency Anemia
deficiency in iron equals to the deficiency to hemoglobin and when you have no hemoglobin, RBC's start to die faster which that leads to an anemia (low RBC count)
Megaloblastic Anemia
caused by impaired DNA synthesis that results in enlarged red cells, vitamin B12 and folic acid deficiencies are the most common conditions
Vitamin B12 Anemia
also known as cobalamin, its essential for DNA synthesis and nuclear maturation, which in turn leads to normal red cell maturation and division, it is also involved in reaction that prevents abnormal fatty acids from being incorporated into neuronal lipids, it prevents neurologic complications, dietary deficiency of B12 is rare because it is found in most dairy products, meats and fish. It is only prevalent in strict vegetarians
Prenicious Anemia
caused atrophic gastritis (stomach inflammation), and attendant failure to produce intrinsic factor that leads to failure to absorb vitamin B12, when vitamin B12 is deficient, the red cells are abnormally large because excess cytoplasmic growth and structural proteins that is not regulated by the vitamin B12, cells are shown to have immature nuclei and show evidence of cellular destruction, they also have a flimsy membrane and an oval rather than biconcave shape, vitamin B12 deficiency uses the Shilling test, and measures 24-hour urinary exertion of radiolabeled vitamin B12
Folic Acid-Deficiency Anemia
very very similar to B12 deficiency, alot of very similar symptoms except for the neurologic symptoms, its also required for DNA synthesis and red cell maturation, its deficiency produces the same type of megaloblastic red changes that occur in vitamin B12 deficiency, methorexate, analog used in the treatment of cancers impairs action of folic acid by blocking its convertion to the active form thus keeping it inactive
Aplastic Anemia
aplasia (lack thereof), disorder of pluripotent bone marrow stem cell that results in reduction of all 3 hemopoietic cell lines (RBC, WBC, and platelets), aplastic anemia results from the failure of the marrow to replace senescent red cells that are destroyed and leave the circulation. Causes: exposure to high radiation, chemicals, and toxins that suppress hemopoiesis directly or through immune mechanisms
Chronic Disease Anemia
results from a complication of chronic infections, inflammation, and cancer, the most common causes of chronic disease anemias are acute and chronic infections, including AIDs and osteomyelitis; cancers auto-immune disorders such as rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease; and chronic disease, chronic renal failure almost always result in anemia, primaryily because of a deficiency of erythropoietin
Transfusion Therapy
provides the means for replacement of red blood cells and other blood components, anemias are treated with transfusions of whole blood or red blood cells only when oxygen delivery to the tissues is compromised, most anemias are treated with transfusions of red cell concentrate, which supple only the blood component that is deficient
ABO Blood Groups
RBCs contain surface antigen and reciprocal antibodies in the serum, 4 major ABO blood groups determined by the presence or absence of two red cell antigens, usually not present at birth but begin to develop at 3-6 months of age and reach maximum levels between the ages of 5-10 years
Type A Blood
has type A antigens and type B antibodies
Type B Blood
has type B antigens and type A antibodies
Type O Blood
has no antigens but type A and B antibodies
Type AB Blood
has A and B antigens but no antibodies
Rh Types
the presence of the D antigen mean that blood cell is Rh positive, the absence of the D antigen means that blood cell is Rh negative, 80% of people who are Rh negative develop Rh positive antibodies if they become exposed to Rh positive blood
THIS SET IS OFTEN IN FOLDERS WITH...