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what is another term for RBCs?
erythrocytes
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What cells contain the oxygen-carryting protein hemoglobin?
RBCs or erythrocytes
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What is a pigment that gives whole blood its red color?
hemoglobin
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A healthy adult male has about ___ million RBCs per microliter of blood, and a healthy adult female has about ___ million
5.4 million
4.8 million
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How many microliters is one drop of blood?
50 microliters
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In order to maintain normal numbers of RBCs, new mature cells must enter the circulation at the rate of at least __ ___ per second, a pace that blanaces the equally high rate of RBC destruction
2 million
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What is the shape of RBCs?
biconcave discs (donut shaped)
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Do RBCs have a nucleus?
no
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Can RBCs carry on extensive metabolic activities?
no
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What does the cytosol of RBCs contain?
hemoglobin molecules
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Why are the hemoglobin molecules in RBCs important?
They are synthesized before loss of the nucleus during RBC production and constitute about 33% of the cell's weight
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Since RBCs have no nucleus, what is the internal space used for?
oxygen transport
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How is it that RBCs do not use up any of the oxygen they transport?
They lack mitochondria and generate ATP anaerobically (without oxygen)
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How does the shape of RBCs contribute to its function?
It has a much greater surface area for the diffusion of gas molecules into and out of the RBC
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What does a hemoglobin molecule consist of?
a protein called globin, composed of 4 polypeptide chains; a ringlike nonprotein pigment called a heme is bound to each of the 4 chains. At the center of each heme ring is an iron ion that can combine reversibly with one oxygen molecule, allowing each hemoglobin molecule to bind 4 oxygen molecules. Each oxygen molecule picked up from the lungs is bound to an iron ion.
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What happens as blood flows thru tissue capillaries?
the iron-oxygen reaction reverses. hemoglobin releases oxygen, which diffuses first into the interstitial fluid and then into cells
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How much of the total carbon dioxide does hemoglobin transport?
about 23%
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what is a waste product of metabolism?
carbon dioxide
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How does hemoglobin transport carbon dioxide?
Blood flowing through tissue capillaries picks up carbon dioxide, some of which combines with amino acids in the globin part of hemoglobin. As blood flows through the lungs, the carbon dioxide is released from hemoglobin and then exhaled
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How does hemoglobin play a role in the regulation of blood flow and blood pressure?
the gaseous hormone nitric oxide (NO)binds to hemoglobin. Under some circumstances, hemoglobin releases NO. The released NO causes vasodilation, an increase in blood vessel diameter that occurs when the smooth muscle in the vessel wall relaxes
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What is vasodilation?
an increase in blood vessel diameter that occurs when the smooth muscle in the vessel wall relaxes.
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How is vasodilation helpful?
Vasodilation improves blood flow and enhances oxygen delivery to cells near the site of NO release
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How long do RBCs live?
about 120 days
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Why do RBCs have such a short life span?
because of the wear and tear their plasma membranes undergo as they squeeze thru blood capillaries
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Why can't RBCs synthesize new components to replace damaged ones?
They don't have a nucleus and other organelles
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what happens to the plasma membrane as the RBCs age?
it becomes more fragile and the cells are more likely to burst, especially as they squeeze thru narrow channels in the spleen
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What happens to RBCs that are ruptured?
they are removed from circulation and destroyed by fixed phagocytic macrophages in the spleen and liver, and the breakdown products are recycled
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What does free iron ions do to molecules in cells or in the blood?
bind to and damage them
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Because free iron ions bind to and damage molecules in cells or in the blood what act as protective protein escorts during transport and storage of oron ions?
transferrin and ferritin
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plasma contains virtually no free ___
iron
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the amount of iron present in the body builds up, is called...
iron overload
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does our bodies have a method for eliminating excess iron?
no
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What are some common consequences of iron overload?
diseases of the liver, heart, pancreatic islets, and gonads
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What is erythropoiesis?
the production of RBCs
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Where does erythropoiesis start and with what?
it starts in the red bone marrow with a precursor cell called a proerythroblast
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what is a reticulocyte?
After a proerythroblast divides several times, a reticulocyte is produced when a cell near the end of the development sequence ejects its nucleus and becomes a reticulocyte
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what causes the RBCs distinctive biconcave shape?
Loss of the nucleus of the cell
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How do reticulocytes get from the red bone marrow into the bloodstream?
by squeezing between the endothelial cells of blood capillaries
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How long does it take for a reticulocyte to become a mature RBC?
1-2 days after their release from red bone marrow
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What happens if the oxygen carrying capacity of the blood falls because erythropoiesis is not keeping up with RBC destruction?
a negative feedback system steps up RBC production
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what is cellular oxygen deficiency called?
hypoxia
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How does hypoxia occur?
if too little oxygen enters the blood
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What does hypoxia trigger?
it stimulates the kidneys to step up the release of erythropoietin, which speeds the development of proerythroblasts into reticulocytes in teh red bone marrow
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What happens when the number of circulating RBCs increase?
more oxygen can be delivered to body tissues
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What kind of problems can reduce oxygen delivery to body tissues?
high altitudes, anemia and circulatory problems
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Why do premature newborns often exhibit anemia?
because in part to inadequate production of erythropoietin
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How is the rate of erythropoiesis measured?
by a reticulocyte count
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What would a low retic count in a person maybe indicate?
a shortage of erythropoietin or an inability of the red bone marrow to respond to EPO, perhaps because of a nutritional deficiency or leukemia
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What would a high retic count maybe indicate?
a good red bone marrow response to previous blood loss or to iron therapy in someone who had been iron deficient. It could also indicate illegal use of Epoetin alfa by an athlete.
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