Ch. 18: lymphatic system

• Cardiovascular System (Blood)


  Made up of cellular elements & extracellular matrix
• Cellular elements (formed elements)


  • Red blood cells (RBCs)
  • White blood cells (WBCs)
  • Platelets

  
• Extracellular matrix


  Plasma, makes blood unique among connective tissues because it is fluid
• Hematocrit


  Measures the percentage of RBCs, clinically known as erythrocytes
• Buffy coat


  Located above the erythrocytes, contains WBCs (leukocytes) and platelets (thrombocytes)
• Packed cell volume


  Volume of erythrocytes after centrifugation
• Blood


  • Bright red (oxygen rich)
  • Dusky red (oxygen poor)
  • Viscous and sticky to the touch
  • Temperature (about 38 ºC or 100.4 ºF)
  • pH range from 7.35 to 7.45, averages about 7.4
• Blood makes up 8 percent of adult body weight
• Adult males average about 5 to 6 liters of blood, adult females average 4–5 liters
• Plasma composition


  • Water (92%)
  • Proteins (Albumin, Globulins, Fibrinogens)
• Hemopoiesis (hematopoiesis)


  1. Before birth: Liver, spleen, lymphatic tissue, red bone marrow

  2. After birth: Red bone marrow in cranial and pelvic bones, the vertebrae, the sternum, and the proximal epiphyses of the femur and humerus
• Hemopoietic stem cell or hemocytoblast


  Lymphoid stem cells give rise to leukocytes (lymphocytes), Myeloid stem cells give rise to erythrocytes, megakaryocytes, and myeloblast (neutrophils, eosinophils, basophils)

  
• Erythropoietin


  Secreted by kidneys in response to low oxygen levels, prompts the production of erythrocytes
• Thrombopoietin


  Produced by the liver and kidneys, triggers development of megakaryocytes into platelets
• Cytokines


  Colony-stimulating factors (CSFs) trigger the differentiation of myeloblasts into granular leukocytes, Interleukins are signaling molecules important in hemopoiesis

  
• Erythrocytes (RBCs)


  • Males have 5.4 million per microliter (μL) of blood, females have 4.8 million per μL
  • Diameter of 7–8 micrometers (μm)
  • Function in O2/CO2 transport
  • Reticulocytes are immature RBCs in circulation
  • Biconcave disks, plump at their periphery and very thin in the center
  • Live up to 100-120 days
  • Approximately 5,000,000 in one drop of human blood!
• Hemoglobin


  Large molecule made up of proteins and iron, consists of four folded chains of a protein called globin, each bound to a red pigment molecule called heme containing an iron (Fe2+) ion

  
• Oxyhemoglobin


  Hemoglobin picks up oxygen and binds to iron ions (bright red)

  
• Deoxyhemoglobin


  Hemoglobin releases some of the oxygen molecules (darker red)

  
• Carbaminohemoglobin


  CO2 binds to Hb
• Types of Anemia


  • Sickle cell disease (sickle cell anemia)
  • Iron deficiency anemia
  • Megaloblastic anemia (Vit B12 deficiency &/or folate)
  • Pernicious anemia (Poor B12 absorption)
  • Thalasemia
• Leukocytes (WBCs)


  • There are only 5000 to 10,000 per μL
  • Larger than erythrocytes
  • Only formed elements that are complete cells
  • Leave the capillaries through emigration or diapedesis
• Types of Leukocytes


  • Granular leukocytes: Neutrophils, Eosinophils, Basophils
  • Agranular leukocytes: Lymphocytes, Monocytes
• Neutrophils


  • 50–70 percent of total leukocyte count
  • Stain chemically neutral
  • Nucleus has a distinct lobed appearance with two to five lobes
  • Polymorphonuclear (polys)
  • Responders to site of infection, efficient phagocytes with preference for bacteria
  • Granules include lysozyme, oxidants, defensins
• Eosinophils


  • 2–4 percent of total leukocyte count
  • Stain best with acidic eosin stain
  • Nucleus has two to three lobes
  • Granules include antihistamine molecules, toxic to parasitic worms
  • High counts in allergies, parasitic worm infestations, autoimmune diseases

  
• Basophils


  • Less than one percent of total leukocyte count
  • Stain best with basic (alkaline) stains
  • Contain large granules that pick up a dark blue stain, intensify inflammatory response
  • Share trait with mast cells, release histamines and heparin
  • High counts in allergies, parasitic infections, hypothyroidism
• Lymphocytes


  • 20–30 percent of all leukocytes
  • High counts in viral infections
  • Three major groups: Natural killer cells, B cells, T cells

  
• Monocytes


  • 2–8 percent of total leukocyte count
  • Indented or horseshoe-shaped nuclei
  • Macrophages are monocytes that have left circulation, phagocytize debris, release antimicrobial defensins and chemotactic chemicals

  
• Leukocyte Disorders


  • Leukopenia (too few leukocytes)
  • Leukocytosis (excessive leukocyte proliferation, often nonfunctional)
  • Leukemia (cancer involving leukocytes, chronic or acute)
  • Lymphoma (cancer of T and/or B lymphocytes)
• Platelets (Thrombocytes)


  • Fragments of megakaryocyte cytoplasm
  • Typically 150,000–160,000 per μL of blood
  • Remain only about 10 days
  • Critical to hemostasis
• Platelet Disorders


  • Thrombocytosis (too many platelets, may trigger unwanted blood clots)
  • Thrombocytopenia (blood may not clot properly, excessive bleeding)