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More Blood (Leukocytes (WBCs) are the only formed element (complete cell…

- - - - Lymphocytes (25-45%): mount immune responses by direct cell attack or via antibodies
        
        2 types of lymphocytes
        
        B-cells: give rise to plasma cells, which produce antibodies
        
        T-cells: act against virus-infected cells and tumor cells
        
        General info
        
        Crucial to immunity
        
        Second most numerous WBC, accounts for 25%
        
        Large, dark purple, circular nuclei with thin rim of blue cytoplasm
        
        mostly found in lymphoid tissue (ex: lymph nodes, spleen), but a few circulate in blood
        
        Production and lifespan
        
        Interleukins are numbered (i.e., IL-3, IL-5)
        
        Colony-stimulating factors (CSFs) are named for WBC type they stimulate (i.e. granulocyte-CSF stimulates granulocytes)
        
        Leukopoiesis: production of WBCs are stimulated by two types of chemical messengers from red bone marrow and mature WBCs
        
        All leukocytes originate from hemocytoblast stem cell that branches into two pathways
        
        lymphoid stem cells produces lymphocytes
        
        myeloid stem cells produce all other elements
      - Monocytes (3-8%): Function=phagocytosis; develop into macrophages in the tissues
    - - 3 types
        
        Basophils (0.5-1%): Bilobed (2?)nucleus, purplish-black cytoplasmic granules. Release histamine and other mediators of inflammation; contain heparin (anticoagulant)
        
        Eosinophils (2-4%): Bilobed (2) nucleus, red cytoplasmic granules. Kill parasitic worms and play complex role in allergy and asthma
        
        Neutrophils (50-70%): multilobed nucleus, pale red and blue cytoplasmic granules. Phagocytize bacteria
      - General info
        
        Larger and shorter lived than RBCs
        
        Cytoplasmic granules stain specifically with Wright's stain
        
        All are phagocytic to some degree
        
        Contain lobed, rather than circular nuclei
  - - - Leukocytosis: WBC count over 11,000 per microliter
- - - - Agglutinate and clog small vessels
      - Rupture and release hemoglobin into bloodstream
      - Result in
        
        Diminished oxygen-carrying capacity
        
        Decreased blood flow beyond blocked vessel
        
        Hemoglobin in kidney tubules can lead to renal failure
  - - - Antigen: anything perceived as foreign that can generate an immune response
      - RBC antigens are referred to as agglutinogens because they promote agglutination
- - - - Mitosis occurs but no cytokinesis, resulting in large stage IV cell with multilobed nucleus
    - - Projections break off into platelet fragments
- - - - Positive feedback cycle: as more platelets stick, they release more chemicals, which cause more platelets to stick and release more chemicals
      - Platelet plugs are fine for small vessel tears, but larger breaks in vessels need additional step
      - von Willebrand factor helps to stabilize platelet-collagen adhesion
      - When activated, platelets swell, become spiked and sticky, and release chemical messengers
        
        ADP causes more platelets to stick and release their contents
        
        Serotonin and thromboxane A_2 enchance vascular spasm and platelet aggregation
      - Platelets stick to collagen fibers that are exposed when vessel is damaged
        
        Platelets do not stick to intact vessel walls because collagen is not exposed
        
        Also, prostacyclins and nitric oxide secreted by endothelial cells act to prevent platelet sticking
      - Step 3: Coagulation (blood clotting) (1-5 min depending on size of wound)
        
        blood is transformed from liquid to gel
        
        Series of reactions use clotting factors (procoagulants), mostly plasma proteins
        
        Numbered I to XIII in order of discovery
        
        Vitamin K needed to synthesize four factors
        
        reinforces platelet plug with fibrin threads
        
        blood clots are effective in sealing larger vessel breaks
        
        Coagulation occurs in three phases: total of 13 procoagulants or blood clotting factors used
        
        Phase 2: becomes thrombin (II_a)
        
        Phase 3: ultimately becomes cross-linked fibrin mesh
        
        Phase 1: Intrinsic (vessel endothelium ruptures, exposing underlying tissues) vs extrinsic (tissue cell trauma exposes blood to tissue factor): funnels to prothrombin activator
        
        Clot retraction and fibrinolysis: Clot must be stabilized and removed when damage has been repaired
        
        Fibrinolysis: process whereby clots are removed after repair is completed. begins within 2 days and continues for several days until clot is dissolved
        
        Plasminogen, plasma protein that is trapped in clot, is converted to plasmin, a fibrin-digesting enzyme
        
        Tissue plasminogen activator(tPA), factor XII, and thrombin all play a role in conversion process
        
        Clot retraction (vessel is healing even as clot retraction occurs)
        
        Contraction pulls on fibrin strands, squeezing serum from clot
        
        serum is plasma minus clotting proteins
        
        Draws ruptured blood vessel edges together
        
        Actin and myosin in platelets contract within 30-60 minutes
        
        Platelet-derived growth factor (PDGF) is released by platelets
        
        Stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall
        
        Vascular endothelial growth factor (VEGF) stimulates endothelial cells to multiply and restore endothelial lining
        
        Disorders of Hemostasis
        
        2 major types of disorders
        
        Thromboembolic disorders: result in undesirable clot formation
        
        Bleeding disorders: abnormalities that prevent normal clot formation: thromocytopenia, impaired liver function, hemophilia
        
        Disseminated intravascular coagulation (DIC)
        
        Involves both widespread clotting and severe bleeding
        
        Can occur in septicemia (bloodstream infection), incompatible blood transfusions, or complications in pregnancy
    - - Direct injury to vascular smooth muscle
      - Chemicals released by endothelial cells and platelets
      - pain relfexes