1 Oxygen and Carbon Dioxide Transport in the Blood Barbara Dziedzic Blood Functions • Substance distribution – Blood transports: • Oxygen and necessary metabolic substrates to the cells of the body • CO 2 and waste products to the lungs and kidneys for elimination • Hormones from endocrine glands to target organs • Regulation: – maintaining homeostasis • regulate pH • adjust body temperature • blood osmotic pressure & blood volume
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Oxygen and Carbon Dioxide Transport in the Blood
Barbara Dziedzic
Blood Functions• Substance distribution
– Blood transports:• Oxygen and necessary metabolic substrates to the cells of the
body• CO2 and waste products to the lungs and kidneys for
elimination• Hormones from endocrine glands to target organs
• Formed elements: Cellular components suspended in the plasma – 45%
• Normal volumes of blood:– Plasma: ~ 2,6 L– Formed elements: ~ 2.4 L– Whole Blood: 4 to 6 L average or 7% to 9% of
the total body weight.
Blood composition and volume
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• RBCs (erythrocytes)• WBCs (leukocytes)
– Granular leukocytes• neutrophils, eosinophils, and basophils
– Agranular leukocytes• lymphocytes and monocytes.
• Platelets (thrombocytes)
Formed elements of blood
Hematocrit
• Hematocrit (Hct) is percentage of total blood volume occupied by red blood cells (RBC) – Normal men – 39 - 49%– Normal women – 33 - 43%– Testosterone stimulates
synthesis of erythropoietin– Low Hct – anemia– High Hct - polycythemia
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Production of Formed Elements• Hematopoiesis : Process of blood cells production.• Hematopoiesis occurs in the red bone marrow• Pluripotential Hematopoietic Stem Cells – from
these cells all types of blood cells are derived. • They give rise to daughter cells, which in turn
differentiate into progenitor stem cells– lymphoid progenitor cell – gives rise to the T and B
lymphocytes.– myeloid progenitor cell – gives rise to the leukocytes,
GM-CSF, M-CSF, G-CSF and IL-3, IL-1, IL-2, IL-5, IL-6, IL-10, IL-11, LIF– stimulate the proliferation and survival of the
progenitor cells– are essential for survival of the progenitor cells– are responsible for differentiation and
maturation of cells– they act in a paracrine fashion.
Erythropoiesis• Erythropoiesis
– is the production of erythrocytes in the bone marrow
– is dependent on the release of erythropoietin(EPO) from the kidneys
– EPO • increases RBC production 7x (up to 17
million/second) • speeds maturation of RBC
• Hypoxia is a main stimulus for RBC production– Decreased oxygen availability (↓ O2 in air) – ↓ RBCs– ↑ tissue demand for oxygen
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Use and abuse of erythropoietin
• Epoeitin alfa – EPO produced by recombinant DNA technology– is used in the treatment of anemia associated with
renal failure, chronic disease or chemotherapy. – is frequently abused by athletes to increase their
hemoglobin levels and improve performance without having to train at altitude.
• it can lead to dangerously high hematocrit, with risk of blood clotting in arteries due to slow blood flow.
Steps in Erythropoisis
Proerythroblast
BasophilicErythroblast
PolychromatophilicErythroblast
OrthochromatophilicErythroblast
Reticulocyte
Erythrocyte
Early Intermediate Late
• A stem cell is transformed into a committed cell called:proerythroblast
• Proerythroblasts develop into erythroblasts
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Steps in Erythropoisis
Proerythroblast
BasophilicErythroblast
PolychromatophilicErythroblast
OrthochromatophilicErythroblast
Reticulocyte
Erythrocyte
Basophilic erythroblast – ribosome synthesis.Polychromatophilic erythroblast – hemoglobin accumulation Orthochromatophilic erythroblast – ejection of the nucleus Reticulocytes become mature erythrocytes in 5 - 7 days.Reticulocytes: 0.5 to 1.5 % of RBCs.
Nutritional requirements for RBC production• Erythropoiesis also depends on adequate supplies of
the amino acids, iron, amino acids, iron, vitamins vitamins BB1212((cyanocobalamincyanocobalamin) and ) and folic acidfolic acid
• Reduced B12 or folate levels adversely affect cell division and maturation– There is a reduction in the RBC count. – RBC are abnormally large (macrocytes) –macrocytic
anemia.• Inadequate iron supply causes that hemoglobin
synthesis is restricted.– RBCs contain less hemoglobin than normal (hypochromic)
and are smaller than normal (microcytic).
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Pernicious Anemia
Blood smear from a person with pernicious anemia. Note the neutrophil hypersegmentation
Patient with severe iron deficiency anemia. In addition, there is marked anisocytosis and poikilocytosis as well as microcytosis
Microcytosis
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Erythrocytes - characteristics• Filled with hemoglobin (Hb)• Biconcave disk shape (thin center and thicker