Describe the sites of hematopoiesis in various age groups
Embryo = fetal yolk sac
Fetus = bones, liver, spleen
Child = long and short bones
Adult = all bones, but bone marrow biopsy only performed the iliac crest of the pelvis and sternum)
How is hematopoiesis regulated?
Development potential is only realized in the presence of colony-stimulating factors. Most CSF’s produced in bone marrow. Interleukins produced by macrophages and T lymphocytes stimulate as well as erythropoietin (kidney).
Describe the pathways of differentiation of pluripotent hematopoietic stem cells.
All cell lineages originate from a developmentally pluripotent stem cell. This common precursor gives rise to developmentally restricted stem cells: erythromyeloid stem cells and lymphoid stem cells.
The descendants of these intermediated stem cells are mature T and B lymphocytes, erythrocytes, neutrophils, monocytes, eosinophils, basophils, and megakaryocytes.
Compare serum and plasma and explain which one you would collect for various blood tests.
Serum = defibrinated plasma (contains all proteins except fibrinogen, prothrombin, coag factors)
Plasma = typically used for the study of clotting disturbances
Explain the molecular structure of hemoglobin.
Heme = oxygen binding part (must have iron), has four pyrrole rings held together by iron in the ferrous form. On degradation, iron and globin are reutilized, while pyrrole gives rise to bilirubin.
Hemoglobin consists of four heme groups and four globins. Globin has four polypeptide chains (alpha, beta, gamma, and delta).
Describe the major events in the life of erythrocytes.
Live in circulation for 120 days.
- nucleated RBC precursors, stimulated by erythropoietin, form erythroctes in the bone marrow.
- normal synthesis of hemoglobin occurs only in the presence of nutrients, iron, b12, and folic acid
- mature RBCs released into circulation
- old and defective RBCs are degraded in the spleen
- iron and globin reutilized stat, bilirubin released in bile
Explain the significance of various erythrocytic parameters such as MCV, MCH, and MCHC, and describe how they are measured.
MCV = mean volume of each RBC, calculated by HCT/RBC count, Nl 83-99 fL
lo = < 80 microcytic anemia
hi = >100 macrocytic anemia
MCH = denotes content of hemoglobin per each RBC, HGB conc. divided by RBC count, Nl 28-32 pg/cell
MCHC = concentration of hemoglobin in red blood cells, HGB/HCT, Nl 32-36 g/dL
What are the normal values for a white blood cell count?
Compare neutrophils and lymphocytes
Neutrophils - short-lived and survive no more than 4 days in peripheral circulation. Bone marrow contains three times more WBC precursors than erythroid precursors
Lymphocytes - long-lived
What is the function of platelets
Essential clotting factors. Derived from megakaryocytes, have no nuclei. 8-10 days in circulation.
What is anemia?
= the reduction of hemoglobin in RBCs below normal
females = < 11.5 g/dL
males = <13 g/dL
Provide an etiologic and a morphologic classification of anemias
- decreased hematopoiesis
- abnormal hematopoiesis
- increased loss or destruction of RBC
Which anemias are caused by decreased hematopoiesis?
aplastic anemia (bone marrow failure)
myelophthisic anemia secondary to BM replacement with TUMOR cells
- multiple myeloma
- folic acid
- multiple myeloma
- folic acid
Which anemias are caused by abnormal hematopoiesis?
sickle cell anemia
Structural protein defects
Which anemias are caused by increased loss or destruction of RBCs?
Immune hemolytic anemia
List typical examples of normocytic, microcytic, and macrocytic anemia.
massive blood loss
chronic liver disease
B12/folic acid deficiency
List typical examples of anemias that present with abnormal red blood cell shapes.
Explain the pathogenesis and pathology of aplastic anemia.
aplastic anemia = pancytopenia (generalized bone marrow failure)
Two forms: idiopathic, secondary (drugs, radiation, virus)
BM is depleted of hematopoietic cells, and consists of fibroblasts, fat cells, scattered lymphocytes
Clinical features: uncontrollable infections, bleeding tendency *most patients dies of overhwelming infection
List the causes of iron deficiency anemia.
iron deficiency = most common form of anemia
more prevalent among women
depletion of body iron (chronic blood loss)
Can be caused by
1. increased iron loss
2. inadequate iron intake/absorption
3. increased iron requirements (growth, PG)
Note: the bone marro shows normal hematopoiesis but contain reduced number of hemosiderin laden macrophages
anisocytosis = variation in size
poikilocytosis = variation in shape
What are the critical events in the metabolism of iron in the human body
1. Uptake of heme or ferrous iron occurs in the intestine.
2. Iron transported on transferrin to the liver or bone marrow.
3. Transferrin binds to RBC precursors in the BM and delivers iron for incorporation into hemoglobin.
4. RBC in the circulation contain 60-80% of body iron.
5. Old RBCs are destroyed in the spleen.
6. The iron is bound to transferrin for recirculation.
7. 20-30% of iron is stored in the form of hemosiderin in the spleen, liver, BM. *esp stroma, can see with Prussian blue
8. Remaining iron is in the respiratory ezymes of somatic cells.
Iron is lost by desquamation of skin and intestinal cells.
Explain the pathogenesis of megaloblastic anemia
B12 or folic acid = 2 essential cofactors for DNA synthesis
RBCs do not mature, but transform to megaloblasts.
BM hypercellular, many megaloblasts
Clinical: destruction of posterior and lateral columns in the SC result in loss of vibration, proprioception, DTR
Compare anemia caused by vitamin B12 with anemia caused by folic acid deficiency.
- binds to IF in the terminal ileum
- treated with IV
- abosrbed in the duodenum and jejunum
- treated with oral
Compare hemolytic anemia caused by intracorpuscular defects with anemia caused by extracorpuscular factors.
Common to all the conditions = anemia, compensatory erythroid hyperplasia of the BM, hyperbilirubinemia, jaundice
When does jaundice appear?
When bilirubin in serum exceend 2-3 mg/dL
Explain the pathogenesis of sickle cell anemia.
formation of abn hemoglobin S d/t genetic defect in the beta chain (subs. of valine for glutamine)
- <40% HbS asymptomatic
- 40-80% HbS mild/moderate
- >80% HbS typical disease
* symptoms only occur in homozygotes
Pathogenenisis of Sickle Cell
Hbs >> polymerization at low O2 tension
Symptoms noticed at 1-2 years of age b/c fetal hgb replaced by HbA.
Sickling crisis: anoxic situations, avoid mountain climbing, strenuous exercise, pregnancy, respiratory disease, fever
Sickle Cell Pathology
Multiple infarcts in various organs
Spleen: repeated infarcts, becomes fibrotic and shrinks
Sickle Cell Clinical Features
- retarded IQ and neurologic deficits
- cardiopulmonary insufficiency
- recurrent infections
Explain the pathogenesis of thalassemia
In contrast to sickle cell, defect is quantitative, not qualitative.
HbA has four chains: 2 alpha, 2 beta
2 genes >> beta chains
4 genes >> alpha chains
** Note: b/c there are only 2 beta genes, these anemias are MORE SEVERE. Beta is more common, and thalasessemia minor.