Red Blood Cells Flashcards
Describe an erythrocyte (RBC)
most numerous blood cell, small, biconcave, easily deforms, contains oxygen carrying hemoglobin
Where are RBC produced and what is their life span?
myeloid or bone marrow stem cells, live for 120 days
What are the 3 general causes of anemia?
excessive blood loss, excessive destruction of rbc’s and deficient production.
What is a reticulocyte and how does it look on a smear?
It’s a premature RBC and is larger and contains a blue staining nucleus
How long does it take for RBC to develop from stem cell to reticulocyte?
1 week
How long for reticulocyte to mature?
24-48hrs
Where is oxygen sensed and what hormone stimulates RBC production?
sensed in the kidneys 90% and liver 10%, erythropoietin
What is erythropoiesis?
RBC production
What governs erythropoiesis?
tissue oxygen needs, anything that decreases oxygen transported in the blood will stimulate RBC production
What causes loading and unloading of O2 on hemoglobin?
when the pressure of O2 is high(lungs), O2 binds to hemoglobin, when the pressure is low (capillaries) the O2 unloads
How does erythropoietin act on the bone marrow?
Binds to receptors on committed stem cells to promote maturation, promotes hemoglobin synthesis, increases membrane proteins
What does an iron deficiency do to RBC production?
hemoglobin production is deficient, percentage of hemoglobin in the cells falls and the volume of the rbc decreases, smaller cells microcytic.
How many polypeptide chains are in one hemoglobin and what 2 types are there?
4 chains, 2 each of Beta and Alpha chains (called hemoglobin A)
Where and in what % is iron distributed in the body?
80% in the heme complex of hemoglobin in the blood, 20% stored in the bone marrow, liver, spleen and other organs
What is the carrier for Iron in the plasma?
Transferrin
How is Iron stored in the liver?
on ferritin
How is the Iron of dead RBC recycled?
The hemoglobin is phagocytized by macrophages and the iron is released back into the blood stream where it is carried by transferrin to the bone marrow for use in new RBC or to the liver for storage on ferritin
What is another by-product of macrophages recycling hemoglobin?
bilirubin
How many molecules of Iron are on a hemoglobin?
4, 1 on each chain
What is hemolytic anemia?
premature destruction of RBC’s
What are the two general hemoglobinopathies that can cause RBC hemolysis?
- Abnormal substitution of an amino acid in the hemoglobin molecule (sickle cell anemia)
- Defective synthesis of one of the polypeptide chains that form globin (Thalassemias)
Describe sickle cell trait vs sickle cell disease
trait is heterozygote (40-45% of hemoglobin affected)-virtually asymptomatic. disease is homozygote (80-95% of hemoglobin affected)
Describe the pathophysiology of sickle cell disease`
At low O2 HbS becomes sickled, there’s a formation of elongated crystals inside the rbc, rbc can’t pass through small capillaries, and spiked ends of crystals rupture membranes
Where do old RBC self destruct?
In the spleen by passing through small spaces that split the cells.
How sickle cell manifested?
severe hemolytic anemia, chronic hyperbilirubinemia, acute pain episodes, infarction, atypical pneumonia from pulmonary infarction, bone crises from marrow infarcts and swelling, neurologic complications, and organ failure from vessel occlusion (spleen very susceptible)
What increases sickling?
Anything that reduces the affinity of hemoglobin to oxygen (hypoxia, cold, stress, exertion, acidosis)
How do you manage sickle cell disease?
No cure, avoid hypoxia, pain control, hydration, control infections, blood transfusions in crises. For children prophylactic antibiotic (Penicillin) from 2mo-5yo and vaccinations
What are thalassemias?
inherited disorders of hemoglobin synthesis from defective synthesis of the alpha or beta chains of adult hemoglobin
What affect does spleen damage have on the patient?
predisposed to life-threatening infections by encapsulated organisims (strep, pneumoniae, HIB, klebsiella)
What is the leading cause of death in sickle cell disease?
Acute chest syndrome-sickling causes pulmonary vessel occlusion-pulmonary infarction-pneumonia-sob, fever, cp, cough-respiratory insufficiency with hypoxia
What are the two types of thalassemia?
either impaired alpha or beta chain production, excess of the other one, overall reduced hemoglobin production
What population is beta type thalassemia most common in?
Mediterranean descent
What population have higher prevalence of both types of thalassemia?
African descent
What will a peripheral smear of thalassemia look like and what are expected MCHC/MCV results?
hypochomic microcytic anemia. MCHC-measures color-will be lower (hypochromic). MCV-size of RBC-will be smaller (microcytic)
What does beta thalassemia cause build up of?
Heinz bodies is the bone marrow (excess alpha chains)
What are the different levels of alpha thalassemia?
1-chain coding gene deleted-asymptomatic
2-mild hemolytic anemia
3-chronic moderate hemolytic anemia
4-Hb Bart’s-death in utero or after birth
What are the levels of beta thalassemias?
heterozygous-usually enough hemoglobin to prevent severe anemia. homozygous-transfusion dependent anemia evident at 6-9 months
What are the complications of beta thalassemias?
severe growth retardation if not treated early due to increased hematopoiesis-bone marrow expansion that impairs bone growth and causes abnormalitites. spenomegaly, iron overload. manage with frequent transfusions and iron chelation therapy to remove iron. bone marrow transplant is potential cure
What is the most prevalent thalassemia?
beta thalassemia trait minor
What does the red cell distribution width (RDW) tell us?
it’s the dispersion of values about the mean, the greater the number the larger variation in cell sizes.
you can have a normal RDW and still have abnormal sized RBC, (all larger or all smaller, small variance)
What does mean corpuscular volume (MCV) tell us?
the average size of the RBC’s
What is deficiency of G6PD?
an inherited enzyme RBC defect. RBC’s are vulnerable to oxidants and denature easily forming Heinz bodies. hemolysis occurs as RBC’s move through the spleen
How does carbon monoxide cause problems?
CO binds to hemoglobin with much greater affinity than O2 forming COHb resulting in impaired oxygen transport
What happens to lead when it enters the body?
it is stored in the bone and eliminated by the kidneys.
What problems does lead cause?
inactivated enzymes, competes with calcium for incorporation into the bone, interferes with nerve transmission and brain development.
What are the major targets of lead toxicity?
RBC’s, GI tract, Kidneys, Nervous system
How does lead cause anemia?
competes with enzymes required for hemoglobin synthesis and iron recycling. Resulting RBC’s are microcytic and hypochromic similar to iron defficiency. Basophil strippling-dots on basophils, decreases RBC lifespan
What are lead poisoning symptoms/signs?
acute abdominal pain, lead lines on bones, diffuse kidney damage, Burton’s line (dark line on teeth), nervous system effects (lower IQ, poor school performance)
What is the most severe acute manifestation of lead poisoning?
acute encephalopathy-persistent vomiting, ataxia, seizures, papilledema, impaired consciousness, coma
What is the criteria for lead poisoning on a screening?
> 5ug/dL is considered positive, do a blood smear to identify microcytic hypochromic anemia
How do you treat lead poisoning?
REMOVE THE SOURCE and use chelating agents to remove the lead ( d-penicillamine, succimer, dimercaprol, edetate disodium calcium)
How does acidosis affect hemoglobin?
It lowers the affinity of hemoglobin to oxygen
What is the normal body blood pH range?
7.35-7.45
What are normal hemoglobin levels in a lab test?
13.5-16.5 males, 12-15 females
What does a hematocrit test tell us?
volume of red cell mass in 100ml of plasma
What does MCHC tell us?
concentration of hemoglobin in RBC’s, Color
Describe hypochromic anemia?
RBC are pale with increased central pallor, HgB is lower (what adds the pigment), RBC’s normally small, caused by Fe deficient anemia and thalassemia
What lab results are seen with microcytic anemia?
small RBC’s, MCV is decreased, normally MCHC decreased too
What lab results are seen with macrocytic anemia?
large RBC’s, hemoglobin is down
What is anisocytosis?
RBC’s are unequal size, RDW larger (more variance in size), differentiates btw FE deficiency anemia and thalassemia
What is polycythemia?
Too many RBC’s, either more RBC’s or decreased plasma volume, caused by bone marrow problems, malignancy, low O2. Can be secondary to increased EPO, high altitudes, hypoxia from sleep apnea or COPD
What are the types of normochromic anemias?
aplastic, post-hemorrhagic, hemolytic and anemias of chronic disease
What is poikilocytosis?
abnormal shaped RBC’s, disks are thinner than normal especially in the middle, abnormal if greater than 10% of cells
