chapter 18

• Erythrocytes


  Red concave discs
• Erythrocytes are heaviest and settle first
• Buffy coat


  Layer containing white blood cells and platelets
• Plasma


  47% to 63% of total blood volume, complex mixture of water, proteins, nutrients, electrolytes, nitrogenous wastes, hormones, and gases
• Major categories of plasma proteins


  • Albumins
  • Globulins (antibodies)
  • Fibrinogen
• Nitrogenous compounds in blood plasma


  • Free amino acids from dietary protein or tissue breakdown
  • Nitrogenous wastes (urea) that must be excreted, primarily by urinary system
• Major proteins of the blood plasma


  • Albumin
  • Alpha (α) Globulins
  • Beta (β) Globulins
  • Gamma (γ) Globulins
  • Fibrinogen
• Albumin


  Responsible for colloid osmotic pressure; major contributor to blood viscosity; transports lipids, hormones, calcium, and other solutes; buffers blood pH
• Alpha (α) Globulins


  Transport and defense functions
• Beta (β) Globulins


  Transport lipids, iron, and aid in destruction of toxins and microorganisms
• Gamma (γ) Globulins


  Antibodies that combat pathogens
• Fibrinogen


  Becomes fibrin, the major component of blood clots
• Electrolytes in blood plasma


  • Sodium (Na+)
  • Calcium (Ca2+)
  • Potassium (K+)
  • Magnesium (Mg2+)
  • Chloride (Cl-)
  • Bicarbonate (HCO3-)
  • Phosphate (HPO42-)
  • Sulfate (SO42-)
• Nitrogenous wastes in blood plasma


  • Urea
  • Uric acid
  • Creatinine
  • Creatine
  • Ammonia
  • Bilirubin
• Other components in blood plasma include dissolved CO2, O2, and N2
• Enzymes and hormones are also present in blood plasma
• Nutrients in blood plasma


  • Glucose
  • Amino acids
  • Lactate
  • Total lipid
  • Cholesterol
  • Fatty acids
  • High-density lipoprotein (HDL)
  • Low-density lipoprotein (LDL)
  • Triglycerides
  • Phospholipids
  • Iron
  • Trace elements
  • Vitamins
• Hypoproteinemia


  Deficiency of plasma proteins, can be caused by extreme starvation, liver/kidney disease, or severe burns
• Kwashiorkor


  Severe protein deficiency in children, characterized by thin arms/legs, swollen abdomen, and edema due to lack of albumin
• Formed elements of blood


  • Erythrocytes (red blood cells)
  • Thrombocytes (platelets)
  • Leukocytes (white blood cells)

  
• Types of white blood cells


  • Granulocytes: Neutrophils, Eosinophils, Basophils
  • Agranulocytes: Lymphocytes, Monocytes
• Hematopoietic stem cells (HSCs)


  Multipotent stem cells in bone marrow that give rise to all formed elements of blood

  
• Erythrocyte production


  1. Hematopoietic stem cells give rise to erythrocyte colony-forming units

  2. Erythrocyte colony-forming units produce erythroblasts

  3. Erythroblasts multiply and synthesize hemoglobin, then discard nucleus to form reticulocytes

  4. Reticulocytes mature into fully formed erythrocytes

  
• Erythrocytes


  • Discoid cells with a biconcave shape, 7.5 μm diameter and 2.0 μm thick at rim
  • Lose nearly all organelles during development, lack mitochondria and nucleus, no protein synthesis or mitosis
• Hemoglobin


  33% of erythrocyte cytoplasm, facilitates oxygen delivery to tissues and enhances carbon dioxide transport to lungs
• Carbonic anhydrase


  Enzyme in erythrocyte cytoplasm that produces carbonic acid from carbon dioxide and water, important role in gas transport and pH balance
• Hemoglobin structure


  Four polypeptide subunits (globins), adult hemoglobin has two alpha and two beta chains, fetal hemoglobin has two alpha and two gamma chains, four heme groups that bind oxygen

  
• Hypoxemia (low oxygen)


  Kidney produces erythropoietin to stimulate bone marrow and increase red blood cell count
• Blood doping


  Either freezing and reinjecting one's own blood, or injecting synthetic erythropoietin to increase red blood cell production
• Life and death of erythrocytes


  Macrophages in liver and spleen digest membrane bits, separate heme from globin, remove iron from heme, convert heme to biliverdin and then bilirubin, which is released into blood plasma and removed by the liver

  
• Polycythemia


  Excess of red blood cells, can be primary (cancer of erythropoietic cell line) or secondary (causes include dehydration, emphysema, high altitude, physical conditioning)

  
• Dangers of polycythemia include increased blood volume, pressure, and viscosity, which can lead to embolism, stroke, or heart failure
• Causes of anemia


  • Hemorrhagic (bleeding)
  • Hemolytic (red blood cell destruction)
  • Inadequate erythropoiesis or hemoglobin synthesis (kidney failure, iron deficiency, pernicious anemia)
• Malaria


  Parasite Plasmodium passes from mosquito to human liver, multiplies asexually in liver cells, then invades and multiplies in red blood cells, causing cyclic fever
• Sickle-cell disease


  Recessive allele modifies hemoglobin structure, causing red blood cells to become rigid, sticky, and pointed, leading to blocked blood vessels and complications

  
• Heterozygotes for sickle-cell allele (one normal, one sickle) are resistant to malaria
• Leukocytes


  Least abundant formed element of blood, protect against infectious microorganisms and other pathogens, spend only a few hours in the bloodstream before migrating to connective tissue

  
• Types of granulocytes


  • Neutrophils
  • Eosinophils
  • Basophils
• Regions where sickle cell trait is most common


  • Mostly areas of Africa
  • Southern Asia
  • The Mediterranean
• Recessive allele


  Modifies structure of Hb (makes HbS)