Chapter 23 Flashcards
Red blood cell development
. Erythroblasts are continuously being formed from the pluripotent stem cells in the bone marrow
- They move through a series of divisions to develop into mature red blood cells.
- Normoblast to reticulocyte, the red blood cells accumulates hemoglobin as the nucleus condensed and is lost.
- The red cell loses its mitochondria and ribosomes.
Function of the red blood # 1
. Transportation of oxygen to the tissues
- Hemoglobin binds some carbon dioxide and carried it from the tissues to the lungs
- The hemoglobin molecule is composed of two pairs of structurally different polypeptide chains.
. Each of the four polypeptide chains consist of a globin (protein) portion and heme unit, which surrounds an atom of iron that binds oxygen
Function of red blood # 2
- Each molecule of hemoglobin can carry four molecules of oxygen
. The production of each type of globin chain is controlled by individual structural genes with five different gene loci
-Mutations can occur anywhere in these five loci
Erythropoiesis
. Red cells are produced in the red bone marrow after birth
. Until 5 years of age, almost all bones produce red cells to meet growth needs; after 5 years, bone marrow activity gradually declines.
. After 20 years, red cell production takes place mainly in the membranous bones of the vertebrae, sternum, ribs and pelvis.
. With this reduction in activity, the red bone marrow is replaced with fatty yellow bone marrow.
Hemoglobin Structure
. Globin -a -B beta . Heme -Iron -porphyrin . Oxygen binding
Red Blood Cell destruction
. The red blood cell has a life span of approximately 120 days
- It is broken down in the spleen
- The degradation products (iron and amino acids) are recycled.
. The heme molecule is converted to bilirubin and transported to the liver.
- it is removed and rendered water soluble for elimination in the bile.
Bilirubin
. The heme unit is converted to bilirubin
. Bilirubin is insoluble in plasma and attached to plasma proteins for transport
- unconjugated
. Removed from the blood by the liver and conjugated with glucuronide to render it water soluble
- conjugated
. Jaundice
Laboratory Tests for Red Blood Cells # 1
. Red blood Cell count ( RBC)
-Measures the total number of red blood cells in 1 mm 3 of blood
. Percentage of reticulocytes ( normally approximately 1%)
-Provide an index of the rate of red cell production
Laboratory Test for Red Blood Cells # 2
. Hemoglobin ( grams per 100 mL of blood)
- Measures the hemoglobin content of the blood
. Hematocrit
- Measures the volume of red cell mass in 100 mL of plasma volume
Transfusion Therapy
. Provides the means for replacement of red blood cells and other blood components
. Four major ABO blood types are determined by the presence or absence of two red cells antigens : A and B
- The presence of D antigen determines the Rh- positive type
- The absence of the D antigen determines the eh negative type
Red blood cell components used in transfusion therapy
. Whole blood .Red blood cells . Leukocytes reduced blood cells . Washed red blood cells . Frozen red blood cells
Signs and symptoms of transfusion Reactiond
. Sensation of heat along the vein where the blood is being infused
. Flushing of the face
. Urticaria, headache, pain in the lumbar area
. Chills, fever, constricting pain in the chest
. Cramping pain in the abdomen
. Nausea, vomiting
. Tachycardia, hypotension, and dyspnea
Anemia
. Definition
- An abnormally, low number of circulating red blood cells or level of hemoglobin, or both
- Results is diminished oxygen- carrying capacity
. Causes
- Excessive loss or destruction of red blood cells
- Deficient red blood cell production because of a lack of nutritional elements or bone marrow failure
Manifestations of Anemia
. Impaired oxygen transport with resulting compensatory mechanisms
. Reduction in red cell indices and hemoglobin levels
. Signs and symptoms associated with the pathological process that is causing the anemia
Anemias of deficient red cell production
. Iron deficiency anemia . Megaloblastic anemia - Cobalamin deficiency anemia - Folic acid deficiency anemia . Aplastic anemia . Chronic disease anemia
G6PD
. A hereditary deficiency of glucose -6 phosphate dehydrogenase predispose to oxidative denaturation of hemoglobin, with resultant red cell injury and lysis
Intravascular and extracvascular hemolysis
. Extra vascular hemolysis occurs when red blood cells become less deformable, making it difficult for them to transverse the splenic sinusoids
. Intravascular hemolysis occurs as a results of complement fixation in transfusion reactions, mechanical injury, or toxic factors.
Sickle Cell Disease and Thalassemias
. Sickle cell disease is an inherited disorder in which an abnormal hemoglobin leads to chronic hemolytic anemia, pain, and organ failure
. The thalassemias are a group of inherited disorders of hemoglobin synthesis leading to decreased synthesis of either the a- or b globin chains of HbA
Cause of sickling in sickle cell disease
. The abnormal structure of Hbs results from a point mutation in the b chain of the hemoglobin molecule, with an abnormal substitution of a single amino acid, valine, for glutamic acid
Iron deficiency Anemia
. Iron deficiency is a common worldwide cause of anemia affecting people of all ages. The anemia results from dietary deficiency, loss of iron through bleeding, or increased demands.
. Because iron is a component of heme, a deficiency leads to decreased hemoglobin synthesis and consequent impairment of oxygen delivery.
Vitamin B12 Deficiency
. The hallmark of vitamin B12 deficiency is megaloblastic anemia
. When vitamin B12 is deficient, the red cells that are produced are abnormally large because of excess cytoplasmic growth and structural proteins.
Causes of Aplastic Anemia
. Among the causes of aplastic anemia are exposure to high doses of radiation, chemicals, and toxins that suppress hematopoiesis directly or through immune mechanisms
Polycythemia # 1
. Definition
- A condition in which the red blood cell mass is increased
. Types
- Relative polycythemia: : results from a loss of vascular fluid and is corrected by replacing the fluid
Polycythemia # 2
- Primary polycythemia: a proliferative disease of the bone marrow with an absolute increase in total red blood cell mass accompanied by elevated white cell and platelet counts
- Secondary polycythemia: results from increased erythropoietin levels caused by hypoxia conditions such as chronic heart and lung disease
