Anatomy - test 1

• The cardiovascular system is a series of tubes filled with fluid connected to a pump
• Blood is composed of plasma and formed elements
• Blood plasma is mostly water and contains plasma proteins, electrolytes, nutrients, hormones, gases, and waste products
• Plasma proteins include albumin, globulins (immunoglobulins, antibodies), prothrombin, and fibrinogen
• Formed elements of blood include red blood cells (erythrocytes), platelets (thrombocytes), and white blood cells (leukocytes)
• Hematocrit is the amount of total blood volume occupied by cells
• Blood cell formation, or hematopoiesis, occurs in the red marrow of flat and irregular bones, and ends of long bones
• Blood cell formation involves pluripotent stem cells, myeloid stem cells, lymphoid stem cells, and various growth factors like erythropoietin and thrombopoietin
• Erythrocytes are biconcave disks without a nucleus or mitochondria, containing hemoglobin that carries oxygen and carbon dioxide
• Blood groups are based on the presence or absence of various antigens on red blood cells
• The ABO typing system categorizes blood into types A, B, AB, and O based on the presence of A and B antigens
• Rh blood groups are determined by the presence of the Rh antigen on red blood cells
• Incompatible blood transfusions can lead to agglutination and serious complications
• The life cycle of red blood cells involves erythropoiesis, circulation, and recycling in the spleen and liver
• White blood cells include basophils, neutrophils, eosinophils, lymphocytes, and monocytes
• Neutrophils are the most abundant white blood cells, with lobed nuclei and fine granules in the cytoplasm
• Basophils have large, dark purple granules and an irregular, S-shaped, bilobed nucleus
• Eosinophils have granules that stain red, and they play a role in the immune response
• Basophils:

  • % of circulating WBCs
  • Large, dark purple, variable-sized granules that stain with basic dyes
  • Irregular, S-shaped, bilobed nucleus
• Eosinophils:

  • % of circulating WBCs
  • Large, uniform-sized granules that stain orange-red with acidic dyes
  • Nucleus has 2-3 lobes connected by thin strand(s)
• Monocytes:

  • % of circulating WBCs
  • Largest WBC in circulating blood (12-20 µm in diameter)
  • Foamy blue-gray cytoplasm
  • Kidney or horse-shoe shaped nucleus
  • Migrate to the tissues soon after formation, differentiate into macrophages
  • Fixed groups found in some tissues (e.g., alveolar macrophages in lungs)
  • Wandering macrophages accumulate at sites of infection
• Lymphocytes:

  • % of circulating WBCs
  • Numbers vary
  • Cytoplasm sky blue in color
  • Dark, oval to round nucleus may occupy most of cytoplasm
• WBC Physiology:

  • Less numerous than RBCs
  • 1 WBC for every 700 RBC
  • Leukocytosis = WBC count due to microbes, strenuous exercise, anesthesia, surgery
  • Leukopenia = WBC count due to radiation, shock, chemotherapy
• Emigration and Phagocytosis of WBCs:

  • WBCs roll along endothelium, stick to it, and squeeze between cells
  • Adhesion molecules help stick WBCs to endothelium
  • Neutrophils and macrophages migrate to injury site by chemotaxis (attracted by toxins produced by microbes and kinins from injured cells)
  • Phagocytose bacteria and debris
• Neutrophil Function:

  • First WBCs to arrive at scene of infections
  • Contain lysozyme (bactericidal enzyme), defensins (antibiotic proteins), superoxidants
• Basophil Function:

  • Involved in inflammatory and allergic reactions
  • Secrete chemicals of inflammation (histamine, heparin, serotonin)
  • Stimulate inflammatory response
• Eosinophil Function:

  • Leave capillaries, enter tissue fluid
  • Release histaminase and other enzymes that combat effects of inflammatory mediators in allergic reactions
  • Combat parasitic worms
  • High count suggests allergic reaction or parasitic infection
• Monocyte Function:

  • Slower to arrive at infection site but arrive in larger numbers, destroy more microbes
  • Enlarge and differentiate into macrophages
  • Clean up cellular debris and microbes following infection
• Lymphocyte Functions:

  • B cells destroy bacteria and inactivate bacterial toxins
  • B cells produce antibodies when stimulated by foreign antigens
  • T cells secrete perforin (enzyme that perforates cell membranes) and are effective against various pathogens
  • Helper T cells stimulate T- and B-cells, activate macrophages, necessary for immunity
  • Regulatory T cells help prevent hypersensitivity reactions, regulate the immune system
  • Natural killer cells attack microbes and some tumor cells
• Differential WBC Count:

  • Indicates inflammation or infection
  • Differential count (count of each type of WBC as % of total WBCs) indicates type of pathology (infection, poisoning, leukemia, chemotherapy, parasites, or allergy reaction)
• Platelet (Thrombocyte) Anatomy:

  • Disc-shaped cellular fragments 2-4 µm in diameter
  • Normal count = 150,000-400,000 cells/mm3 of blood
• Complete Blood Count (CBC):

  • Screens for anemia and infection
  • Includes total RBC, WBC, platelet counts, differential WBC, hematocrit, hemoglobin
• Hemostasis:

  • Stoppage of bleeding when blood vessels are damaged
  • Three mechanisms: vascular spasm, platelet plug formation, coagulation (clotting)
• Vascular Spasm:

  • Immediate contraction of damaged vessel wall
  • Reduces blood loss for several minutes to several hours
  • Allows time for other hemostatic mechanisms to proceed
• Platelet Plug Formation:

  • Platelet adhesion, release reaction, aggregation
• Coagulation (Clotting):

  • Cascade of reactions resulting in the formation of fibrin threads
• Role of Vitamin K:

  • Produced by bacteria in the large intestine
  • Required for normal clotting
  • Not involved in clot formation but required for synthesis of several clotting factors
• After clot has formed:

  • Platelets pull on fibrin threads (retraction) drawing edges of damaged vessel closer together
  • Serum can still escape, but cells cannot
  • Eventually new endothelium grows, and scar tissue produced by fibroblasts
  • Breakdown of small, intravascular clots and clots at a site of completed repair by tissue plasminogen activator (t-PA)
• Hemostatic Control Mechanisms:

  • Fibrin, prostacyclin, anticoagulants
  • Low dose aspirin inhibits vasoconstriction and platelet aggregation
  • Clot formation remains localized because fibrin absorbs blood dispersing clotting factors
  • Prostacyclin opposes platelet adhesion and release
  • Anticoagulants (e.g., heparin, antithrombin) block or inactivate various clotting factors
• Thrombolytic Agents:

  • Injected to dissolve clots and restore circulation
  • Directly or indirectly activate plasminogen (e.g., streptokinase, t-PA)