HOW BLOOD IS PRODUCED • Red bone marrow produces all seven formed elements • Pluripotent stem cells (PPSC) • Formerly called hemocytoblasts or hemopoietic stem cells • Colony-forming unit—specialized stem cells only producing one class of formed element of blood • Myeloid hemopoiesis—blood formation in the bone marrow • Lymphoid hemopoiesis—blood formation in the lymphatic organs (beyond infancy this only involves lymphocytes)
ERYTHROCYTES Two principal functions • Carry oxygen from lungs to cell tissues • Pick up CO 2 from tissues and bring to lungs Insufficient RBCs can cause death in minutes due to lack of oxygen to tissues Disc-shaped cell with thick rim • Lack mitochondria • Anaerobic fermentation to produce ATP • Lack of nucleus and DNA • No protein synthesis or mitosis
SICKLE CELLSHereditary defects that occur mostly among people of African descent
QUANTITIES OF ERYTHROCYTES AND HEMOGLOBIN RBC count and hemoglobin concentration indicate amount of O 2 blood can carry • Hematocrit (packed cell volume): percentage of whole blood volume composed of RBCs • Men 42% to 52% cells; women 37% to 48% cells • Hemoglobin concentration of whole blood • Men 13 to 18 g/dL; women 12 to 16 g/dL • RBC count • Men 4.6 to 6.2 million/ L; women 4.2 to 5.4 million/ L
IRON METABOLISM Iron—key nutritional requirement • Lost daily through urine, feces, and bleeding • Men 0.9 mg/day and women 1.7 mg/day • Low absorption rate of iron requires consumption of 5 to 20 mg/day
IRON METABOLISM Dietary iron: ferric (Fe 3+ ) and ferrous (Fe 2+ ) • Stomach acid converts Fe 3+ to absorbable Fe 2+ • Gastroferritin binds Fe 2+ and transports it to small intestine • Absorbed into blood and binds to transferrin for transport to bone marrow, liver, and other tissues - Bone marrow for hemoglobin, muscle for myoglobin, and all cells use for cytochromes in mitochondria Liver apoferritin binds to create ferritin for storage
IRON METABOLISM Vitamin B 12 and folic acid • Rapid cell division and DNA synthesis that occurs in erythropoiesis Vitamin C and copper • Cofactors for enzymes synthesizing hemoglobin • Copper is transported in the blood by an alpha globulin called ceruloplasmin
ERYTHROCYTE HOMEOSTASIS Negative feedback control • Drop in RBC count causes hypoxemia detected by kidney •
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