Erythrocytes Flashcards
Erythropoiesis
process of RBC formation
RBC made in
Bone marrow under influence of erythropoietin (EPO) produced by the kidneys
Characteristics of RBC
no nucleus (enucleate) or organelles (mitochondria, golgi, etc)
Packed with Hb (hemoglobin)
No DNA/RNA aka no cell division
Major role carries O2 and CO2 away from tissues
RBC shape
highly flexible biconcave disk
Flexibility of RBC is for
maximizing surface area for gas exchange and passage through small capilaries
Where are RBC produced
Bone Marrow; 7 days for maturation
How are RBC eliminated?
Spleen
Reticulocytes
immature RBC. They are bigger than normal RBC. Have a small amount of ribosomal RNA but no nucleus
Reticulocyte count
accurate way to assess body’s response to anemia
Low reticulocyte count
poor production in bone marrow
anemia due to decreased production of RBC
High reticulocyte count (Reticulocytosis)
more made in bone mature
anemia due to premature destruction of RBCs (hemolysis)
Hemoglobin (Hb)
RBCs packed with hemoglobin = o2 carrying protein
Large protein composed of 4 amino acid chains, global chains, each bound to an iron-containing heme group
Heme group
Consists of iron (Fe) which is the site of O2 binding
Where is the synthesis of heme?
mitochondria and cytoplasm of immature RBCs
Where is globin synthesis?
cytoplasm of ribosomes
During 3 -10 weeks gestation hemoglobin chains are
zeta and epsilon
As a fetus what HB is available?
Hb F alpha2 gamma 2
Has an adult what HB is available?
HBA- HB A1: alpha2beta2, HbA2 alpha2delta2; HB F
What is oxyhemoglobin?
Hemoglobin carrying O2
Carbaminohemoglobin
Hb carrying Co2
Abnormal Hv
Carboxyhemoglobin: binds CO2 instead of O2
Methemoglobin Fe2+ to Fe3+; cano’t bind O2
Erythrocytosis (polycythemia)
increased number off RBC
ANemia, erythropenia (erythrocytopenia)
decreased number of RBC
Poikilocytosis
difference in shape of hemoglobin
Rouleaux
like stacks of coins; due to increase in high molecular weight plasma proteins
Red cell agglutination
due to antibody present in RBC surface forms irregular clumps
Howell-Jolly bodies
large round densely stained inclusions on edge of cell; nuclear reminants
ALWAYS ON EDGE OF CELL
Increased destruction of RBCS
hemolytic anemia
G6PD deficiency
Sicle cell disease
Decreased production of RBC
Iron deficiency anemia
Thalassemia (A,Beta)
Polycythemia
increased # of RBC
Absolute: primary or secondary
Primary: overproduction of RBCS
Secondary: caused by increased secretion due to hypoxia
Relative: due to dehydration or fluid loss (looks like we have more RBC but really don’t)
Polycythemia (Rubra) Vera (PV)
myeloproliferative disease; rare
due to increased RBC proliferation in bone marrow
Possible cause: JAK-2 gene
Anemia
Rate of RBC production does not equal rate of RBC destruction
Iron deficiency anemia
Insufficient iron stores due to poor diet, poor iron absorption, body iron stores are depleted by prolonged bleeding
**most common
Common in menstruating or pregnant women
Sideroblastic anemia
Abnormal incorporation of iron into the heme group of Hb
Toxic accumulation of iron in mitochondria = ringed sideroblasts
Microcytoic anemia
second most common anemia after iron deficiency anemia
Cause: chronic infection, chronic inflammatory diseases (rheumatoid arthritis)
Mechanism: blocked iron transport from storage sites to developing RBC in bone marrow
Microcytic anemias: Thalassemias
Inherited genetic disorader
Reduced or absent production of normal Hb A
2 types: alpha thalassemia- caused by deletion of 1,2,3,4 alpha globin
B thalassemia- caused by mutations in beta global gene cluster
Alpha Thalassemia
deficiency or no synthesis of alpha global chains
Asymptomatic and silent carriers
Alpha Thalassemia major- Hemoglobin Barts Hydrops Fetalis
No survival. Most severe form. Complete absence of alpha global chains. Anemia in utero. Hv F cannot be produced.
Alpha Thalassemia minor (trait)
mildest form; one B global gene is defection
Moderately reduced Hv A1; increased HV A2 and HV F
Low MCV and MCH but high RBCs
no symptoms
Beta Thalassemia major (Cooley’s anemia)
most severe form; both B global games are defection
Reduced or absent Hb A1; increased A2 and HF
Macrocytic anemias
elevated MCV
Impaired DNA synthesis but normal RNA synthesis
Usually due to B12 and folic acid deficiency
which causes neural tube defects (spina bifida)
Hemolytic disorders
Reduction in RBC lifespan and compensatory increase in rate of erythropoiesis
Cause: incompatible blood transfusions, cancer, drugs
Extravascular hemolysis
RBCs by macrophages in spleen, liver, BM
Intravascular hemolysis
RBCs within blood vessels
Intrinsic defect
structural or functional defect within the RBC
Red cell membrane- hereditary spherocytosis
Red cell metabolism- G6PD deficiency
Hb- sickle cell disease and thalassemias
Extrinsic defect
abnomality in RBC environment
immunologic abnomalities
mechanical injury
infectious organism that invade and destruct RBCs or produce toxins
Herditary spherocytosis
most common inherited RBC abnomality
transmitted in autosomal dominant manner but autosomal recessive form also exists
Defective gene encodes for the Red Cell cytoskeletal protein spectrum= rupture
Major site of hemolysis= spleen
G6PD deficiency
The role of G6PD is to protect red cell proteins from endogenous or exogenous oxidant stress
Mechanism: converts glucose –> ribose - 5- phosphate –> NADPH production
NADPH prevents building up of free radicals within the cell
Triggers: ingestion of lava beans -divicine
Reason: production and release of free radicals
Sickle cell disease
genetic. Change in hemoglobin structure due to mutation of Hb gene
Normal Hb: substitution of glutamic acid by valine
Result: distortion of RBC shape from biconcave to half moon. Becomes inflexible rod
Normal RBCS move freely but sickle RBCS get trapped in small capillaries and get destroyed.
Damage organs: spleen, kidneys, liver
