Disorders of RBCs

Question 1

RBC development

Answer 1

-erythroblast are continuously being formed from the pluripotent stem cells in the bone marrow
-move through a series of divisions to develop into mature red blood cells
-Normoblast to reticulocyte, the red blood cell accumulates hemoglobin as the nucleus condenses and is lost
-the red cell loses its mitochondria and ribosomes

Question 2

Function of RBC

Answer 2

transport oxygen to the tissues

Question 3

Erythropoiesis

Answer 3

*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 reduction in activity, the red bone marrow is replaced with fatty bone marrow

Question 4

Hemoglobin structure

Answer 4

*Globin chains
-a
-B
*Heme
-iron
-porphyrin
*oxygen binding

Question 5

RBC destruction

Answer 5

*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

Question 6

The heme molecule is converted to…

Answer 6

Bilirubin and transported to the liver
-it is removed and rendered water soluble for elimination in the bile

Question 7

Bilirubin

Answer 7

*the heme unit is converted to bilirubin
*bilirubin is insoluble in plasma and attaches to plasma proteins for transport
-unconjugated
*removed from the blood by the liver and conjugated with glucuronide to render it water soluble
-conjugated
*Jaundice

Question 8

Lab test for RBCs

Answer 8

*(RBC) -measures the total number of red blood cells in 1 mm3 of blood
*Percentage of reticulocytes (norm approx. 1%)- provides an index of the rate of red cell production
*Hemoglobin- measures the hemoglobin content of the blood
*Hematocrit- measures the volume of red cell mass in 100 ml of plasma volume

Question 9

4 major ABO blood types

Answer 9

the presence of D antigen determines the RH- positive type
absence = Rh- negative

Question 10

G6PD

Answer 10

a hereditary deficiency of glucose-6-phosphate dehydrogenase predisposes to oxidative denaturation of hemoglobin, with resultant red cell injury and lysis

Question 11

Extravascular hemolysis

Answer 11

occurs when red cells become less deformable, making it difficult for them to traverse the splenic sinusoids

Question 12

Intravascular hemolysis

Answer 12

occurs as a result of complement fixation in transfusion reactions, mechanical injury, or toxic factors

Question 13

Sickle cell disease

Answer 13

an inherited disorder in which a abnormal hemoglobin (hemoglobin S [HbS] leads to chronic hemolytic anemia, pain, and organ failure

Question 14

Thalassemias

Answer 14

are a group of inherited disorders of hemoglobin synthesis leading to decreased synthesis of either the a- or b-globlin chians of HbA

Question 15

cause of sickling in sickle cell disease

Answer 15

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 acid, valine, for glutamine acid

Question 16

Iron-deficiency anemia

Answer 16

*results from dietary deficiency, loss of iron through bleeding, or increased demands
-Iron is a component of heme, a deficiency leads to decreased hemoglobin synthesis and consequent impaired of oxygen delivery

Question 17

Vitamin B12 deficiency

Answer 17

*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

Question 18

Causes of aplastic anemia

Answer 18

among the cause of aplastic anemia are exposure to high doses of radiation, chemicals, and toxins that suppress hematopoiesis directly or through immune mechanisms

Question 19

Polycythemia

Answer 19

*a condition in which the red blood cell mass is increased
-3 types

Question 20

Relative polycythemia

Answer 20

results from a loss of vascular fluid and is corrected by replacing the fluid

Question 21

Primary polycythemia

Answer 21

a proliferative disease of the bone marrow with an absolute increase in total RBC mass accompanied by elevated white cell and platelet counts

Question 22

Secondary polycythemia

Answer 22

results from an increased erythropoietin levels caused by hypoxic conditions such as chronic heart and lung disease

Question 23

Polycythemia manifestations

Answer 23

*variable related to an increase in RBCs, hemoglobin level, and hematocrit with increased blood volume and viscosity

splenomegaly, depletion of iron, disrupted cardiac output, hypertension, decreased cerebral blood flow, venous stasis, thromboembolism and hemorrhage

Question 24

Neonatal blood

Answer 24

*hemoglobin concentrations at birth are high, reflecting the high synthetic activity in utero to provide adequate oxygen delivery
-hyperbilirubinemia
-hemolytic disease

Question 25

Aging and RBCs

Answer 25

*Age associated decline in the hematopoietic reserve
-reduction in hematopoietic progenitors
-reduced production of hematopoietic growth factors
-inhibition of erythropoietin
-Inflammatory cytokines interfere with erythropoietin interaction with its receptors
#studies to rule out comorbid conditions