PL 2.2

• Formed Elements


  • Includes 3 principal components: Red blood cells, White blood cells, Platelets
• A significant drop in hematocrit indicates anemia, a lower-than normal number of RBCs
• Hematology


  The branch of science concerned with the study of blood, blood-forming tissues, and the disorders associated with them
• Physical Properties of Blood

  • Blood is denser and more viscous (thicker) than water and feels slightly sticky
  • The temperature of blood is 38C (100.4F), about 1C higher than oral or rectal body temperature
  • A slightly alkaline pH ranging from 7.35 to 7.45
  • The color of blood varies with its oxygen content
  • Blood constitutes about 20% of extracellular fluid, amounting to 8% of the total body mass
  • The blood volume is 5 to 6 liters (1.5 gal) in an average-sized adult male and 4 to 5 liters (1.2 gal) in an average-sized adult female
• Interstitial Fluid


  The fluid that bathes body cells and is constantly renewed by the blood
• Red Blood Cells

  • Contain the oxygen-carrying protein hemoglobin, which gives whole blood its red color
  • Healthy adult male has ~5.4 million red blood cells per μl of blood
  • Healthy adult female has ~4.8 million red blood cells per μl of blood
  • RBCs are biconcave discs
• Blood Plasma


  A straw-colored liquid where the formed elements are removed from blood
• Functions of the Blood

  • Transportation - blood transports oxygen, nutrients, heat and waste products
  • Regulation - helps maintain homeostasis of all body fluids, regulate pH, adjust body temperature
  • Protection - Blood can clot, protect against disease
• Plasma Proteins

  Proteins in blood plasma that maintain proper blood osmotic pressure, which is an important factor in the exchange of fluids across capillary walls
• Components of Blood

  • Blood Plasma (55%) - a watery liquid extracellular matrix that contains dissolved substances
  • Formed Elements (45%) - these are cells and cell fragments
• In polycythemia, the percentage of RBCs is abnormally high, and the hematocrit may be 65% or higher
• Red Blood Cells or erythrocytes


  Contain the oxygen-carrying protein hemoglobin, which is a pigment that gives whole blood its red color
• A significant drop in hematocrit indicates anemia, a lower-than-normal number of RBCs
• Monocytes


  • Can be Fixed macrophages or wandering macrophages
• White Blood Cells


  • Classified as either granular or agranular
• Each platelet is disc-shaped, 2–4 µm in diameter, and has many vesicles but no nucleus
• Platelets


  • Between 150,000 and 400,000 platelets are present in each L of blood
• Granular Leukocytes


  • Eosinophil
  • Basophil
  • Neutrophil
• Lymphocytes may be as small as 6–9 µm in diameter or as large as 10–14 µm in diameter
• Monocytes are large eaters, 12–20 µm in diameter, with a kidney-shaped or horseshoe-shaped nucleus and blue-gray cytoplasm with a foamy appearance
• Platelets, also called thrombocytes, help stop blood loss from damaged blood vessels by forming a platelet plug
• White Blood Cells leave the bloodstream

  By a process termed emigration, formerly called diapedesis, in which they roll along the endothelium, stick to it, and then squeeze between endothelial cells
• Leukopenia is an abnormally low level of white blood cells (below 5000/L)
• White Blood Cells are outnumbered by RBCs by about 700:1
• White Blood Cells make up less than 1% of the formed elements, have nuclei, and do not contain hemoglobin like RBCs
• Red Blood Cells (RBCs)


  Mature RBCs have no nucleus, so all their internal space is available for oxygen transport
• Red Blood Cells (RBCs)


  Biconcave discs with a diameter of 7–8 µm
• Healthy adult female

  • ~4.8 million red blood cells per μl of blood
• Healthy adult male

  • ~5.4 million red blood cells per μl of blood
• Red blood cells live only about 120 days due to the wear and tear their plasma membranes undergo as they squeeze through blood capillaries
• Erythropoiesis


  The production of RBCs starts in the red bone marrow with a precursor cell called a proerythroblast
• Red Blood Cells (RBCs)

  Lack a nucleus and other organelles and can neither reproduce nor carry on extensive metabolic activities
• White Blood Cells can live for several months or years, but most live only a few days
• Three types of lymphocytes

  • T lymphocytes (T cells), B lymphocytes (B cells), and natural killer (NK) cells
• Agranular leukocytes


  White blood cells without granules in their cytoplasm
• Neutrophil


  Smaller, evenly distributed, and pale lilac in color; the nucleus has two to five lobes, connected by very thin strands of chromatin
• Monocytes


  Large eaters; 12–20 m in diameter; The nucleus of a monocyte is usually kidney shaped or horseshoe shaped, and the cytoplasm is blue-gray and has a foamy appearance
• Lymphocyte


  The nucleus is round or slightly indented and stains darkly; The cytoplasm stains sky blue and forms a rim around the nucleus
• Granular leukocytes


  White blood cells with granules in their cytoplasm
• Types of lymphocytes

  • T lymphocytes (T cells)
  • B lymphocytes (B cells)
  • Natural killer (NK) cells