Hematopoiesis - ANSWER-Process of blood cell production in adult bone marrow or the liver and/or
spleen of the fetus
Two stages
▪ Mitosis (proliferation)
▪ Maturation (differentiation)
Primary site of hematopoietic stem cells - ANSWER-Bone marrow ("myeloid tissue")
Difference between red and yellow bone marrow - ANSWER-Red marrow produces RBCs, yellow marrow
does not produce RBCs
Active bone marrow sites - ANSWER-pelvic bones
vertebrae
cranium
mandible
sternum
ribs
humerus
femur
Factors that increase hematopoiesis - ANSWER-(1) conversion of yellow bone marrow, which does not
produce blood cells, to hematopoietic red marrow by the actions of erythropoietin (a hormone that
stimulates erythrocyte production)
(2) faster differentiation of progenitor cells
(3) faster proliferation of stem cells into progenitor cells
,Erythropoiesis - ANSWER-production of RBCs
Sequence of erythropoiesis - ANSWER-Pluripotent hematopoietic stem cell --> committed
Proerythroblast/Pronormoblast --> Erythroblast/Normoblast (Hgb synthesis begins) --> Reticulocyte
(nucleus is lost; 3 days spent in bone marrow, about 1 day in blood) --> Erythrocyte
** aprox. 1% of RBCs are reticulocytes **
In each step the quantity of hemoglobin increases and the nucleus decreases in size
Erythropoietin - ANSWER-A hormone produced and released by the kidney that stimulates the
production of red blood cells by the bone marrow
Always present in plasma
Released in response to low renal oxygenation
- NOT the # of RBCs but rather oxygen delivery
- e RBC production increases within 24 hours; life span 4-12 hours; increased RBC # in 5 days
- Given to dialysis and chemo patients
Reticulocytes - ANSWER-▪ Last immature form of erythroblast
▪ Contains polyribosomes (globin synthesis) and mitochondria (heme synthesis)
▪ 24-48 hours after leaving bone marrow for circulation, matures into erythrocyte
- Loses polyribosomes and mitochondria
-Make up 1-2% of RBCs
- Last about 2 days in bone marrow and 1 day in blood continuing to mature
- During time of low HCT time in marrow decreased to as little as 1 day
,▪ Reticulocyte count -- Indicates whether new RBCs are being produced; good indicator of erythropoiesis
Normal Labs (RBCs, Hgb, Hct, MCV, MCH) - ANSWER-RBCs 4.2-6.1
Hgb 12-18
Hct35-50%
MCV: 78-100 (related to size)
MCH: 27-34 (related to Hgb content)
Reticulocytes: new RBC formation - low suggest issues in production
Microcytic-Hypochromic Anemias - ANSWER-Characterized by red cells that are abnormally small and
contain reduced amounts of hemoglobin
Iron Deficiency Anemia (IDA)
Sideroblastic
Thalassemia
Iron Deficiency Anemia (IDA) - ANSWER-Type of Microcytic-Hypochromic Anemia
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