Exam 1 Mod 1: Hematopoiesis Flashcards
Describe the locations of hematopoiesis
- Blood cell formation occurs in the red bone marrow, which is found in:
- Bones of the axial skeleton and girdles
- Proximal epiphyses of the humerus and femur
Signifigance of the hematopoietic stem cell (HSC)
- Undifferentiated precursor cells
- Hemocytoblast
- Resides in the red bone marrow
- Gives rise to all the formed elements of blood
Explain the basic process of erythropoiesis
1) Hematopoietic stem cell (hemocytoblast)
2) Proerythroblast (committed cell)
3) Basophilic erythroblast (ribosome synthesis)
4) Polychromatic erythroblast (Hemoglobin accumlation)
5) Orthochromatic erythroblasts (ejection of nucleus)
6) Reticulocyte (ejection of nucleus)
7) Erythrocyte
Explain regulation through erythropoietin (EPO)
Erythropoietin (EPO), a glycoprotein, stimulates the formation of erythrocytes. When certain kidney cells become hypoxic (oxygen deficient), oxygen sensitive enzymes are unable to carry out their normal functions of degrading an intracellular signaling molecule called hypoxia-inducible factor (HIF). As HIF accumulates, it accelerates the synthesis and release of erythropoietin.
Regulation with EPO
Define Hypoxic or hypoxia
When certain kidney cells become oxygen deficent
Regulation through EPO
Causes of hypoxia
- Decreased RBC numbers
- Insufficent hemoglobin per RBC (ex. Iron deficiency)
- Reduced availability for O2 (ex. high altitudes)
Significance of the reticulocyte
- Immature erythrocyte
- Named b/c it still contains a scant reticulum (network) of clumped ribosomes
Anemia and three groups based on the cause
Anemia is a condition in which the blood’s oxygen carrying capacity is too low to support normal metabolism
Three group causes:
- Blood loss
- Not enough RBC produced
- Too many RBC being destroyed
Anemia
Group: Blood loss:
Two different
- Hemorrhagic anemia: Rapid blood loss, (example stab wound), treated by replacing the lost blood
- Chronic hemorrhagic anemia: Slight but persistent blood lost (example: hemorrhoids, bleeding ulcer), primary problem must be treated to stop blood loss
Group: Not enough RBC produced
Four different
- Iron deficiency anemia
- Renal anemia
- Pernicious anemia
- Aplastic anemia
Anemia: Not enough RBC produced
Iron deficency anemia
- Can be caused by hemorrhagic anemia, but also by low iron intake or impaired absorption
- RBCs are called microcytes, which are small and pale because they cannot synthesize their normal complement of hemoglobin
Anemia: Not enough RBC produced
Renal anemia
- Caused by lack of EPO, often accompanies renal disease because damaged or diseased kidneys cannot produce enough EPO
Anemia: Not enough RBC produced
Pernicious anemia
- Autoimmune disease that destroys stomach mucosa that produces intrinsic factor
- Intrinsic factor must be present for vitamin B12 to be absorbed by intestinal cells. WIthout vitamin B12, the developing erythrocytes grow but cannot divide, and large pale cells called macrocytes result
Anemia: Not enough RBC produced
Aplastic anemia
- Destruction of red bone marrow
- All formed element cell lines are affected resulting in anemia as well as clotting and immunity defects
- Can be causes by drugs, chemicals, radiation, or viruses
- Blood transfusions provide a stopgap treatment until stem cells are harvested from a donor’s blood, bone marrow or umbilical cord blood can be transplanted
Anemia: Too many RBC being destroyed
Hemolytic anemias
- Premature lysis of RBCs
- Can be caused by:
- Incompatible transfusions or infections
- Hemoglobin abnormalities (usually genetic disorber resulting in abnormal globin): Thalassemias, and sickle cell anemia
