How blood is produced red bone marrow produces all

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

HEMOGLOBIN

SICKLE CELLS
Hereditary 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
•