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Human anatomy and Physiology, Elaine N. Marieb, Katja HoehnTRANSCRIPT
Chapter 10
Blood LectureBlood Composition
Blood
Formed elements living blood "cells" suspended in plasma
Erythrocytes (red blood cells, or RBCs)
Leukocytes (white blood cells, or WBCs)
Platelets Spun tube of blood yields three layers
Hematocrit 47% 5% for males; 42% 5% for females
Physical Characteristics and Volume
Functions of Blood
Distributing substances
Regulating blood levels of substances
Protection
Distribution Functions
Regulation Functions
Protection Functions
Blood Plasma
90% water
Over 100 dissolved solutes
Nutrients, gases, hormones, wastes, proteins, inorganic ions
Plasma proteins most abundant solutes
Remain in blood; not taken up by cells
Proteins produced mostly by liver
60% albumin; 36% globulins; 4% fibrinogen
Albumin
Functions
Formed Elements
Erythrocytes
Erythrocytes
Structural characteristics contribute to gas transport
Biconcave shapehuge surface area relative to volume
>97% hemoglobin (not counting water)
No mitochondria; ATP production anaerobic; do not consume O2 they transport
Superb example of complementarity of structure and function
Erythrocyte Function
RBCs dedicated to respiratory gas transport
Hemoglobin binds reversibly with oxygen
Normal values
Males - 1318g/100ml; Females - 1216 g/100ml
Hemoglobin Structure
Globin composed of 4 polypeptide chains
Two alpha and two beta chains
Heme pigment bonded to each globin chain
Gives blood red color
Heme's central iron atom binds one O2 Each Hb molecule can transport four O2 Each RBC contains 250 million Hb molecules
Hemoglobin (Hb)
O2 loading in lungs
O2 unloading in tissues
CO2 loading in tissues
Hematopoiesis
Hematopoietic stem cells (Hemocytoblasts)
New blood cells enter blood sinusoids
Erythropoiesis: Red Blood Cell Production
Stages
Myeloid stem cell transformed into proerythroblast In 15 days proerythroblasts develop into basophilic, then polychromatic, then orthochromatic erythroblasts, and then into reticulocytes Reticulocytes enter bloodstream; in 2 days mature RBC
Erythropoiesis
As myeloid stem cell transforms
1. Ribosomes synthesized
2. Hemoglobin synthesized; iron accumulates
3. Ejection of nucleus; formation of reticulocyte (young RBC)
Reticulocyte ribosomes degraded; Then become mature erythrocytes
Reticulocyte count indicates rate of RBC formation
Regulation of Erythropoiesis
Hormonal Control of Erythropoiesis
Hormone Erythropoietin (EPO)
Causes of hypoxia
Effects of EPO
Some athletes abuse artificial EPO
Dangerous consequences
Testosterone enhances EPO production, resulting in higher RBC counts in males
Dietary Requirements for Erythropoiesis
Nutrientsamino acids, lipids, and carbohydrates
Iron
Available from diet
65% in Hb; rest in liver, spleen, and bone marrow
Free iron ions toxic
Stored in cells as ferritin and hemosiderin
Transported in blood bound to protein transferrin
Vitamin B12 and folic acid necessary for DNA synthesis for rapidly dividing cells (developing RBCs)
Fate and Destruction of Erythrocytes
Fate and Destruction of Erythrocytes
Heme and globin are separated
Iron salvaged for reuse
Heme degraded to yellow pigment bilirubin
Liver secretes bilirubin (in bile) into intestines
Degraded to pigment urobilinogen Pigment leaves body in feces as stercobilin
Globin metabolized into amino acids
Released into circulation
Erythrocyte Disorders
Anemia
Causes of Anemia
Three groups
Blood loss
Low RBC production
High RBC destruction
Causes of Anemia: Blood Loss
Hemorrhagic anemia Chronic hemorrhagic anemiaCauses of Anemia: Low RBC Production
Iron-deficiency anemia Pernicious anemia Renal anemia Aplastic anemiaCauses of Anemia: High RBC Destruction
Hemolytic anemiasCauses of Anemia: High RBC Destruction
Usually genetic basis for abnormal Hb
Globin abnormal
Fragile RBCs lyse prematurely
Causes of Anemia: High RBC Destruction
Thalassemias Sickle-cell anemia
Hemoglobin S
One amino acid wrong in a globin beta chain
RBCs crescent shaped when unload O2 or blood O2 low
RBCs rupture easily and block small vessels
Poor O2 delivery; pain
Sickle-cell Anemia
Black people of African malarial belt and descendants
Malaria Kills 1 million each year
Sickle-cell gene
Two copies ( Sickle-cell anemia
One copy ( Sickle-cell trait; milder disease; better chance to survive malaria
Sickle-cell Anemia: Treatments
Acute crisis treated with transfusions; inhaled nitric oxide
Preventing sickling
Hydroxyurea induces fetal hemoglobin (which does not sickle) formation
Blocking RBC ion channels
Stem cell transplants
Gene therapy
Erythrocyte Disorders
Polycythemia vera Secondary polycythemiaLeukocytes
Make up