General Pathology Objectives Section 1 Cell Injury and Death 1. Define pathogenesis and distinguish it from etiology or cause. a. Pathogenesis refers to the sequence in cells, tissues, or organism in response to a cause or etiology of the disease process. In most diseases, morphological changes occur that cause functional derangements that produce the clinical signs and symptoms. 2. Define and provide an example of autolysis, necrosis, and apoptosis. a. Autolysis refers to cellular alterations that occur from degradative enzymes released from within the cell. An example is the cellular changes that occur after somatic death or when a tissue is removed from the body. b. Necrosis refers to the cellular alterations of cell death that arise from a loss of cell membrane integrity, resulting in a calcium influx into a cell deprived of ATP. The cell swells before it enters necrosis. Ex. coagulative necrosis, caseous necrosis, etc. c. Apoptosis refers to the cellular alterations of cell death that arise from activation of a class of enzymes called caspases that degrade DNA and cause cytoskeletal changes in the presence of ATP. Caspases are activated when mitochondria lose their integrity. Ex. is when the p53 cascade is activated. 3. List the defining characteristics of reversible cellular injury and define what is meant by the point of no return. a. Reversible cellular injury is characterized by changes in cell size and shape. Before necrosis the cell swells with blebs that lack organelles. Before apoptosis the cell shrinks with blebs that contain organelles. b. At the point of no return, the cell will die even if the cause of injury is removed. Pyknosis, Karyorrhexis, and Karyolysis are morphological determinants of cell death. 4. Identify the mechanisms believed to result in acute cellular swelling, chromatin clumping, and coagulative necrosis. a. Acute cellular swelling is caused when an injury increases permeability of cell membrane to sodium or interfering with the synthesis of ATP that fuels the Na/K pump. Increased intracellular sodium causes cell to gain water and swell. Morphologically, vacuoles containing water appear in cytoplasm. Ischemia is most common cause since it deprives cell of ATP. Acute cellular swelling can be a reversible condition. b. Chromatin clumping is caused by decrease in pH. Ischemia causes a decrease in ATP production, therefore, anaerobic glycolysis attempts to replace loss of ATP, this produces lactic acid decreasing pH. Chromatin clumping is a reversible condition. c. Coagulative necrosis is caused by extensive damage to cell membranes, the cell looses the capacity to regulate calcium and the cytoplasmic calcium concentration increases causing necrosis. Cytoplasm becomes eosinophilic due to protein denaturation and loss of RNA.
5. Distinguish reversible from irreversible injury in terms of microscopic appearance. a. Reversible Injury: Acute cellular swelling (cloudy swelling, hydropic degeneration, vacuolar change); Chromatin clumping; myelin figures (membrane residues) b. Irreversible Injury (Necrosis): Mitochondrial densities (flocculent dense bodies); Eosinophilia; Pyknosis, Karyorrhexis, Karyolysis 6. Identify the principal mechanisms of cell membrane damage that give rise to coagulatvie necrosis and identify clinical states where they occur. Define free radicals, identify their source and discuss their role in cell injury. a. Loss of membrane phospholipids, cuased by ischemia. Ischemia impairs the ATP dependent calcium pump causing increased cytosolic calcium. Calcium activates the phospholipases that initiate membrane injury. b. Lipid peroxidation, caused by free radical injury. Free radicals react with polyunsaturated lipids in membranes causing peroxide formation and cleavage of the fatty acid double bonds. Most lipid peroxidation is due to hydroxyl radical rather than superoxide. c. Direct membrane damage, caused by certain toxic chemicals (ex. mercury binding to sulfhydryl groups increasing membrane permeability), cytopathic viruses, trauma, and immunologic injury. 7. Distinguish coagulative necrosis from apoptosis in terms of examples, significance, basic mechanism, types of DNA damage, and host response. a. Coagulative necrosis is characterized by cell outlines that persist for several days, eosinophilic cytoplasm, and nuclear changes. The cell will first swell. Always pathologic, ATP not required, Multiple cells affected (field of cells), Random DNA degradation, Inflammation b. Apoptosis occurs after the cell shrinks and blebs pinch off that contain organelles. Physiologic and sometimes pathologic, ATP required, Single Cells affected, Site specific DNA breakdown (Endonucleases break down DNA producing regions of 180-200 base pairs, this produces the nucleus fragmentation (karyorrhexis)), No inflammation (phagocytosis of apoptotic bodies) c. The requirement for ATP is what determines whether elevated cytoplasmic calcium results in coagulatvie necrosis or apoptosis. 8. Define the characteristic features of the following types of necrosis and their disease associations. a. Coagulative necrosis: i. Nucleus may be lost, but cellular shape and outline is maintained. ii. Eosinophilic due to protein coagulation b. Caseous necrosis i. Cell outlines are lost but eh necrotic area remains intact ii. The dead cells persist indefinitely as amporphous, granular eosinophic debris iii. Associated with inflammatory reactions and infection (mycobacteria like tuberculosis, and fungi) iv. Giant cells (macrophages) are near the border of the necrosis
c. Enzymatic fat necrosis i. Found in adipose tissue and most commonly the pancreas, also seen in breast due to trauma ii. Released pancreatic lipases split fatty acids from triglycerides and calcium complexes with the released fatty acids giving a white chalk-like appearance (basophilic deposits in stained sections) d. Liquefactive necrosis i. Occurs when enzymes breakdown the tissue quickly and completely to where it becomes liquid, for example in the brain ii. Another example is pus in a boil or an abscess iii. Cell outlines are lost e. Gangrenous necrosis i. Coagulative necrosis caused by absence of blood supply (ischemia) usually of an extremity or portion of bowel f. Fibrinoid necrosis i. Fibrin-like and is used to describe the appearance of blood vessels and connective tissue in certain cases of immunologic (vasculitis, rheumatic fever) or non-immunologic (hypertension) injury ii. Appears eosinophilic, smudgy, and structureless iii. It appears this way due to plasma protein insudation and deposition of fibrin g. Gummatous necrosis i. Gummas occur in the late stage of untreated syphilis and consist of a central area of necrosis often surrounded by lymphocytes. ii. Gummas resemble caseous necrosis but the term gumma is restricted to lesions of syphilis 9. Define hyalin and be able to recognize it in tissue section a. Descriptive term that implies a homogeneous, usually eosinophilic change either intra or extracellular b. Hyalin is amorphous and protein in nature but it is not he same protein in different locations and conditions 10. Distinguish the following in terms of definition, common disease or organ associations and significance: a. Anasarca i. Severe and generalized edema with profound subcutaneous tissue swelling. b. Ascites i. Fluid collection in the peritoneum (hydroperitoneum) ii. Seen in liver damage (liver cirrhosis) c. Fatty change i. Triglycerides accumulate in cells from a variety of pathologic conditions, primarily with toxins, lack of oxygen, and diabetes mellitus ii. Fatty change is a manifestation of reversibly injured cells and it occurs primarily in those cells involved in or dependent upon fat metabolism
d.
e.
f.
g.
iii. Frequently seen in liver, heart, and kidney Steatosis i. Accumulation of fat in hepatocytes ii. Mostly seen in liver since it is the main site of liver metabolism, also seen in heart, muscle, and kidney. iii. Caused by toxins, protein malnutrition, diabetes mellitus, obesity, and anoxia. iv. Present in chronic alcoholics Glycogen accumulation i. Appear as clear vacuoles within the cytoplasm. Staining with PAS reaction gives it a violet color. ii. Occurs with glycogen storage diseases (all genetic). iii. Enzymatic defects in the synthesis or breakdown of glycogen result in massive accumulation, with secondary injury and cell death. Dystrophic calcification i. If necrotic cells (all types of necrosis) and cellular debris are not promptly destroyed and reabsorbed, they tend to attract calcium salts and other minerals and to become calcified. ii. Usually a sign of previous cell injury, but often a cause of organ dysfunction. iii. Hypercalcemia accentuates dystrophic calcification. iv. With H & E stain, calcium slats have a basophilic, amorphous granular, sometimes clumped, appearance. Metastatic calcification i. May occur in normal tissues when there is hypercalcemia. ii. May occur widely through body but principally affects the interstitial tissues of the gastric mucosa, kidneys, lungs, systemic arteries, and pulmonary veins. All these regions lose acid and therefore have an internal alkaline compartment that predisposes them to metastatic calcification. iii. Looks similar to dystrophic calcification.
Inflammation 1. List the cardinal signs of inflammation and explain their pathophysiology. a. Heat and Redness: caused by arteriole dilation and hyperemia b. Swelling: caused by venular permeability and leukocyte emigration creating and exudates c. Pain: caused by chemical mediators (histamine, bradykinin, prostaglandins) d. Loss of Function 2. Describe the purpose of inflammation and its general sequence of events. a. Inflammation is a response to injury of vascularized tissue. Its purpose is to deliver defensive and reparative materials (leukocytes and plasma) to a site of injury.
b. Sequence: Cellualar injury and hemorrhage; Hyperemia and vascular permeability; Leukocyte emigration and function; Return to normal structure or to scar 3. List the cells participating in the inflammatory response and distinguish between them in terms of time and appearance, morphology, source, and function. a. PMN: Characteristic cell of acute inflammation; phagocytic; helps sterilize wound b. Monocyte/Macrophage: Important in late stage of acute inflammation and in chronic inflammation; ingests bacteria and debris; presents antigens; involved in wound repair; monocytes differentiate into macrophages when they leave circulation and enter tissue c. Lymphocytes: B-cell involved in humoral (antibody) immunity and acute inflammation; T-cell involved in cell mediated immunity and chronic inflammation; lymphocytes are present but not prominent in acute inflammation, as antibodies are more important than cellular immunity during acute inflammation; with persistent inflammation, lymphocytes become more prominent and cellular immunity plays an important role in chronic inflammation d. Mast cells: source of histamine; inflammatory mediator e. Platelets: Source of serotonin, platelet activating factor (PAF) and Platelet derived growth factor (PDGF); produced by megakaryocytes in bone marrow 4. In the vascular phase of inflammation, identify the difference between transudate and exudates. Identify sites of vascular leakage and the site of microcirculatory control of hyperemia. a. Transudate is edema fluid with a low protein content b. Exudate is edema fluid with a high protein content that frequently contains inflammatory cells c. Vascular permeability takes place at the venular end of the microcirculation whereas hyperemia occurs at the arteriolar end 5. List five key mediators of vascular permeability generated by the inflammatory response and differentiate among them on the basis of source, chemical composition, and effect. a. Histamine i. Source: Mast cells, basophils, platelets ii. Chemical composition: Amino Acid iii. Effect: Venular leakage through post capillary venule contraction, arteriolar dilation indirectly via NO, contraction of smooth muscle (anaphylaxis) b. Serotonin i. Source: Platelets ii. Chemical composition: Amino Acid iii. Effect: Similar to Histamine c. Bradykinin i. Source: Made from high MW kininogen via intrinsic coagulation system
ii. Chemical composition: Peptide iii. Effect: Vascular permeability through post-capillary venule contraction, vasodilation of arterioles indirectly via NO, affects nerves to produce pain d. Platelet activating factor i. Source: Phospholipase A2 cleavage of phosphatidyl choline followed by acetylation (remodeling pathway) ii. Chemical composition: phosphatidyl choline analogue (lipid) iii. Effect: Vascular permeability through post-capillary venule contraction, vasodilation of arterioles indirectly via NO, acts as a chemotactic agent to cause leukocyte accumulation, contracts smooth muscle (anaphylaxis in bronchiolar smooth muscle) e. Slow reactive substance of anaphylaxis i. Source: SRS-A is composed of leukotrienes derived from arachidonic acid via the lipoxygenase pathway. Phosphatidyl choline is rich in arachidonic acid. SRS-A is compsed of LTC-4, LTD-4, and LTE-4. ii. Chemical composition: Leukotrienes (lipid) iii. Effect: Vascular permeability through post-capillary venule contraction, contracts smooth muscle (anaphylaxis in bronchiolar smooth muscle). (LTB-4 is a chemotactic agent causing leukocyte accumulation) 6. Describe the interrelationships between coagulation, bradykinin formation, complement activation, and fibrinolysis. a. The Hageman factor (factor XII) comes in contact with collagen (due to injury to endothelium) and becomes activated to Factor XIIa (activated Hageman factor). Factor XIIa activates the clotting cascade, which ultimately cleaves fibrinogen to give fibrin. Factory XIIa also cleaves prekallikrein to produce kallikrein. Kallikrein and activated Hageman factor act on high MW kininogen to split off a 9 amino acid residue to give bradykinin. Bradykinin causes vascular permeability. Kallikrein also cleaves plasminogen to give plasmin which activates the complement cascade. b. At the same time that factor XIIa is inducing clotting, it can also activate the fibrinolytic system by activating plasmin. This cascade counterbalances clotting by cleaving fibrin, thereby solubilizing the fibrin clot. Plasmin is important in lysing fibrin clots. c. In conclusion, activated Hageman factor (Factor XIIa) initiates: 1) the kinin system, which produces vasoactive kinins; 2) the clotting system, which induces formation of thrombin, which activates fibrinogen to fibrin; 3) the fibrinolytic system, which produces plasmin and degrades the fibrin; and 4) the complement system, which produces anaphylatoxins. d. It should be evident that coagulation and inflammation are tightly linked.
7. Describe the sequence of events in leukocyte emigration from vessels and the role of adhesion molecules in neutrophil and monocyte diapedesis. Be able to predict the effect of a genetic deficiency of an adhesion molecule. a. Margination – the peripheral orientation of leukocytes that occurs when stasis develops due to microvascular permeability. b. Rolling – Uses interaction between selectins and addressins. P-selectin (pre-formed) and E-selectin (synthesized at time of injury) are on endothelium and L-selectin (constitutive) is on leukocytes. c. Attachment – The beta-2 integrins are present on the surface of leukocytes and are responsible for arresting leukocytes and allowing diapedesis to occur. They are also involved in phagocytosis. LFA-1 is an example that is found on leukocytes and participates in diapedesis. VLA-4 is also an example, but it is not part of the beta-2 integrin family. The integrins bind to endothelial adhesion molecules of the immunoglobulin family. LFA-1 binds to ICAM-1 (constitutive) and VLA-4 binds to VCAM-1(expressed upon endothelial stimulation). d. Transmigration – PECAM-1 is present in the junction between endothelial cells (Robbins says it’s on both leukocytes and endothelial cells) and is involved in transmigration of leukocytes between endothelial cells. 8. Define chemotaxis and distinguish it from chemokinesis. List substances with major chemotactic properties, their source, and the cells attracted. Define and provide examples of chemokines. a. Chemotaxis – the directional movement of cells against a concentration gradient of attractant b. Chemokinesis – increased random movement of the cell in response to a chemical mediator Chemotactic Factor Principal Source Principal Cells Attracted Leukotriene B-4 Neutorphils Neutrophils C-X-C Family: IL-8 Endothelium Neutrophils C5a Complement N-formyl-methionyl peptide Bacteria Neutrophils and monocytes PAF Phosphatidyl choline C-C Family: MCP-1 Endothelium Monocytes TGF-beta Platelets Monocytes, fibroblasts PDGF Platelets, macrophage, Fibroblasts, smooth muscle Fibroblasts, Smooth muscle 9. Describe the sequence of events in phagocytosis and the importance of oxidative burst. Predict the clinical consequence if there were a defect in the oxidative burst. a. Steps: Attachment, oxidative burst, engulfment, phagosome-lysosome fusion. b. During phagocytosis, oxygen is drawn into the cell that is not used in oxidative phosphorylation but is converted to superoxide. Interaction of the particle with the phagocyte membrane activates a membrane NADPH
dependent oxidase that generates superoxide and subsequently hydrogen peroxide. 10. Identify some lysosomal enzymes and their function. a. Acid hydrolases b. Defensins: cationic proteins that bind to cell wall and puncture them c. Lysozyme: Decrade cell wall of bacteria d. Lactoferrin: Binds Fe so that the bacteria can’t use it to sustain life e. Myeloperoxidase (Neutrophils): Produces HOCl from H2O2 11. Compare neutrophils with macrophages in terms of key mechanisms of bacterial killing and principal functions at the inflammatory site. a. Neutrophils i. Uses HOCl for oxygen-dependent killing ii. Contains a large marrow reserve iii. Main function is to control infection by phagocytosis (sterility) b. Macrophages i. Uses hydroxyl radical for oxygen-dependent killing since it doesn’t contain myeloperoxidase ii. No marrow reserve iii. Functions: Debridement (wound cleaning), anti-microbial (phagocytosis), antigen presentation, angiogenesis, fibroplasia 12. Distinguish monocyte differentiation from macrophage activation with respect to reversibility and function. Develop a concept map of the relationship of macrophage activation to cell mediated immunity and explain why this is important in host parasite interactions. a. Monocytes differentiation begins as cells emigrate, changing morphology and function to become macrophages. Differentation appears to be due to specific environmental signals. Differentiation is not reversible. b. Macrophage activation is reversible. Macrophage activation for bactericidal or tumoricidal activity is initiated by INF-gamma derived from CD4 Th1 cells. Macrophages produced IL-12 that stimulates differentiation of CD4 T-helper cells, which produce interferon gamma upon encountering macrophage-associated antigens. IFN-gamma stimulates macrophage production of TNF-alpha, which in turn potentiates the effect of IFN-gamma resulting in full macrophage activation. Macrophage activation is important because it has the capacity to kill intracellular parasites and tumor cells. c. PGE-2 and corticosteroids inactivate macrophages. d. Nitric oxide synthetase (NOS) is induced when macrophages are primed by IFN-gamma. 13. Define the factors that determine if an acute inflammatory response ends with restoration of structure and function or scar formation. a. Capacity of injured tissue to regenerate i. Labile cells and stable cells Fibrous union (restoration) ii. Permanent cells fibrous scar b. Extent of tissue injury i. Extracellular matrix intact restoration
ii. Extracellular matrix damaged fibrous scar c. Amount of granulation tissue i. More granulation tissue that forms increases probability of scar formation 14. Describe how granulation tissue is transformed into connective tissue. List key cells involved in wound repair. Identify the principal cytokines involved in forming new blood vessels, fibroblast proliferation, and collagen formation. Describe how tensile strength of the wound develops. Be able to distinguish healing by first intention from second intention. a. Granulation tissue is an essential process in wound repair and is characterized by the formation of new blood vessels, extracellular matrix, and collagen. Its ultimate purpose is to restore blood supply to the wound and to provide collagen for tensile strength or scar formation. b. Granulation tissue formation: Formed by the processes of angiogenesis and fibroplasia. First macrophages secrete VEGF to stimulate endothelial proliferation causing angiogenesis. Fibroplasia follows angiogenesis. The wound is first filled with fibrin stabilized by plasma fibronectin. As time passes, fibroblasts replace this matrix with collagen type 3 liked by tissue fibronectin and glycosaminoglycans (GAGs). Myofibroblasts are then responsible for wound contracture that facilitates healing. Macrophages secrete IL-1/TNF that causes fibroblasts to secrete procollagenase that is converted to collagenase by the plasmin (enzyme produced during coagulation). Collagenase removes Type 3 collagen at the same time that Type 1 collagen is synthesized in response to TGF-beta. c. Cytokines for forming blood vessels (angiogenesis): i. VEGF ii. Minor role for bFGF d. Cytokines for fibroblast proliferation i. PDGF e. Cytokines for collagen formation i. TGF-beta f. Tensile strength develops by the replacement of type 3 collagen with type 1 collagen through the action of collagenase. Tensile strength also increases by cross-linking of the collagen fibers. Wound achieves about 70-80% of tensile strength of tissue before injury. g. First intention vs. second intention i. First Intention: Healing of a clean, uninfected surgical incision approximated by sutures. The incision causes death of a limited number of epithelial and connective tissue cells as well as disruption of epithelial basement membrane continuity. The narrow incisional space immediately fills with clotted blood containing fibrin and blood cells; dehydration of the surface clot forms the scab that covers the wound. ii. Second Intention: When there is more extensive loss of cells and tissue. Regeneration of parenchymal cells cannot completely restore the original architectures, and hence abundant granulation
tissue grows in from the margin to complete the repair. Large wounds have myofibroblasts that cause contraction, this doesn’t occur in first intention healing. 15. Identify the function of the following mediators of inflammation: a. Bradykinin b. Basic fibroblast growth factor (bFGF) i. Helps with angiogenesis c. Complement components (C3a and C5a) d. Epithelial growth factor (EGF) i. Indirectly causes fibroblast proliferation by causing fibroblasts to secrete PDGF ii. Involved in epithelial regrowth e. Histamine f. Interferon gamma g. Nitric oxide h. Platelet activating factor (PAF) i. Platelet derived growth factor (PDGF) i. Produced in macrophages and megakaryocytes (stored in platelets) and smooth muscle. Produced in fibroblasts when they are stimulated by growth factors for autocrine stimulation. ii. Causes fibroblast proliferation j. Prostaglandin E-2 k. Slow reactive substance of anaphylaxis (SRS-A) l. Transforming growth factor Beta (TGF-Beta) i. Produced in megakaryocytes and stored in platelets. Also made in macrophages and fibroblasts. ii. Growth factor for fibroblasts causing proliferation (type 1 receptor indirectly by causing fibroblast to secrete PDGF) and their secretion of collagen type 3 ( and later type 1 collagen), GAG and tissue fibronectin (type 2 receptor) iii. This effect on fibroblasts causes rapid induction of fibrosis iv. Inhibits angiogenesis m. IL1/Tumor necrosis factor (TNF) i. Secretion of procollagenase from fibroblasts (converted to collagenase by plasmin which removes type 3 collagen and replaces it with type 1 collagen) ii. Growth factor for fibroblasts n. Vasucalr endothelial growth factor (VEGF) i. Derived from macrophages and platelets ii. Causes angiogenesis by stimulating endothelial proliferation 16. List factors that determine the severity, duration and outcome of the inflammatory response. a. Acute inflammatory response can end in resolution, organization with eventual fibrous scar formation, chronic abscess formation, or chronic inflammation.
b. Restoration depends on ability of damaged cells to regenerate, and intact support stroma, and limited formation of granulation tissue. c. Fibrous scar is most likely outcome of acute inflammation when damaged cells can not regenerate, the support stroma has been damaged, and significant amounts of scar tissue formation. d. Chronic abscess formation is formed when an abscess fails to drain and it is transformed into a chronic abscess as collagen forms to wall of the injured area. e. Chronic inflammation may follow an acute inflammatory response that fails to eliminate the agent (persistent or repetitive stimulus) or it may occur without a clinically apparent acute phase. It is recognized by infiltration of mononuclear cells, increased tissue destruction and fibrosis. 17. Distinguish between acute and chronic inflammation on the basis of injurious agent, host response, cellular activity, and morphology. Be able to recognize the gross and microscopic appearance of acute inflammation, chronic inflammation, and chronic granulomatous inflammation. Know the significance of numerous eosinophils in an inflammatory reaction. a. Acute inflammation i. Injurious agent 1. Infections 2. Trauma 3. Physical and Chemical agents 4. Tissue Necrosis 5. Foreign bodies 6. Immune reactions ii. Host response 1. Vascular permeability 2. Vasodilation 3. Emigration of leukocytes iii. Cellular activity 1. chemotaxis 2. leukocyte activation and secretion of cytokines and mediators 3. phagocytosis iv. Morphology 1. dilated capillaries 2. presence of neutrophils 3. exudates 4. eosinophilia b. Chronic inflammation i. Injurious agent 1. Persistent infections 2. Prolonged exposure to potentially toxic agents 3. Autoimmunity ii. Host response 1. Recruitment of monocytes from circulation
2. Activation of macrophages 3. Repair iii. Cellular activity 1. Activation of macrophages 2. Secretion of collagen by fibroblasts (fibrosis) 3. Development of new vessels (angiogenesis) iv. Morphology 1. Mononuclear infiltrate (macrophages and lymphocytes) 2. Fibroblasts 3. Granuloma formation (angiogenesis and fibrosis) 4. Tissue destruction and scar c. Chronic granulomatous inflammation i. Form when phagocytosis fails to neutralize the causative agent. d. Eosinophils i. Seen in allergic inflammation, parasitic infestations, and some forms of chronic inflammation. 18. Differentiate granulomatous inflammation from granulation tissue. List several diseases that are characterized by granulomatous inflammation. Describe the sequence of events leading to giant cells and epithelioid cells. a. Granulation tissue is characterized by the formation of new blood vessles, extracellular matrix, and collagen. Whereas, a granuloma is a nodular collection of modified macrophages, surrounded by lymphocytes found in response to a persistent stimulus. b. Giant cells arise from fusion of macrophages. T-cells are not required, however, fusion can be induced by factors generated by an immune response. After fusion, nuclear division gives rise to multi-nucleated giant cells. This forms a foreign body giant cell which turns into a Langhan’s giant cell after nuclear rearrangement. c. Epithelioid cells are derived from macrophages. Infectious agents cause the release of IFN-gamma and TNF-alpha which activates macrophages. The macrophages have iNOS activity and will eventually lose iNOS activity and become epithelioid cells. d. Granulomas can be caused by infectious agents and inert foreign material. Tuberculosis causes caseating granulomas. 19. Define and be able to use in context the following terms: a. Abscess b. Cellulitis i. Pyogenic inflammation spreading diffusely through subcutaneous tissue c. Chemotaxis d. Diapedesis e. Granuloma f. Granulation tissue g. Margination h. Opsonin i. Purulent inflammation
j. Pus k. Healing by first intention i. Healing of a clean, uninfected surgical incision approximated by sutures. The incision causes death of a limited number of epithelial and connective tissue cells as well as disruption of epithelial basement membrane continuity. The narrow incisional space immediately fills with clotted blood containing fibrin and blood cells; dehydration of the surface clot forms the scab that covers the wound. l. Healing by second intention i. When there is more extensive loss of cells and tissue. Regeneration of parenchymal cells cannot completely restore the original architectures, and hence abundant granulation tissue grows in from the margin to complete the repair. Large wounds have myofibroblasts that cause contraction, this doesn’t occur in first intention healing. m. Fibrinous inflammation n. Suppurative inflammation i. Same as purulent inflammation o. Serous inflammation p. Ulceration 20. Explain how inflammation can cause disease and identify the principal mechanism by which neutrophils and macrophages cause tissue pathology. a. Inflammation causes disease by neutral proteases and oxidants. Serine proteases that degrade extracellular matrix include: elastase and cathepsin G. Matrix metalloproteases (MMPs) that are zinc dependent and degrade extracellular matrix and collagen include: collagenase and stromelysin. These are all found on PMNs and macrophages, except elastase is not present on macrophages. b. Elastase is the main enzyme from PMN’s responsible for connective tissue injury, while the MMPs are the major neutral proteases invlolved in macrophage mediated tissue destruction. In addition, macrophages secrete IL-1/TNF that stimulates fibroblasts to produce collagenase. c. Leukocyte oxidants that injure tissues are the same agents generated to kill microorganisms. d. Neutrophils mediate injury by: i. cytolytic enzyme release: ex. Acute abscess ii. deficiency of alpha-1-antitrypsin due to inactivation by chloramines that were created from HOCl (there is no longer an inhibitor for elastase): ex. emphysema iii. exocytois plus oxidant injury (granulation by high concentration of chemotactic factor or anti-neutrophil antibody, also caused by regurgitation): ex. Hypersensitivity diseases 21. Describe the role of TGF-beta in fibrotic disorders. a. Macrophages produce TGF-beta and PDGF (fibroblast proliferation) for repair. When these cytokines are overproduced, a fibrotic disorder may
result. TGF-beta promotes fibroblast production of collagen ad proteoglycans. TGF-beta can also come from platelets and fibroblasts. b. Seen in atherosclerosis, silicosis, liver cirrhosis, idiopathic pulmonary fibrosis, post-operative adhesions, glomerulosclerosis, and granulomas. Diseases where Neutrophils contribute to tissue injury: Abscess formation Glomerulonephritis Rheumatoid Arthritis Gout Myocardial Infarction System Lupus erythematosis Emphysema Reperfusion injury Vasculitis Acute Respiratory Distress Syndrome Diseases where Macrophages contribute to injury: Atherosclerosis Caseous necrosis Amyloidosis Chronic Inflammation Cachexia Interstitial lung disease
Reheumatoid arthritis Septic shock Silicosis
Thrombosis 1. Define the use in context of the following terms: a. Clotting i. Process of forming fibrin. b. Clot i. Blood coagulum that forms OUTSIDE blood vessels or intravascularly AFTER death. ii. Does NOT require platelets c. Hemostasis i. Events that take place in injured vessels to prevent hemorrhage. d. Hemostatic plug i. Collection of platelets that adhere to collagen via von Willebrand factor. e. Release reaction i. Upon activation of platelets once they bind to collagen, they secrete chemicals from their granules. This helps in platelet aggregation and formation of primary hemostatic plug. ii. Granules contain ADP (changes configuration of fibrinogen receptor (GP IIb/IIIa) allowing fibrinogen to link platelets), calcium, fibrinogen, TxA2 (vasoconstrictor, platelet aggregator) f. Thrombosis i. Mass of fibrin, platelets, and entrapped blood cells that forms WITHIN a vessel or cardiac chamber DURING life. ii. Can be pathologic or physiologic. g. Embolism i. A mass of solid, liquid or gas carried by the blood from one site to another. h. Lines of Zhan i. Gross and microscopic laminations (entrapment of red and white blood cells within a coral-like arrangement of fibrin and platelets)
of thrombi due to their formation in a flowing stream of blood and help distinguish them from clots. i. Mural thrombus i. A non-occlusive thrombus. ii. Tend to occur in aorta or cardiac chambers j. Infarction i. An area of coagulative necrosis caused by occlusion of either an artery or vein ii. Most are due to arterial occlusions by thrombi or emboli k. Active hyperemia i. Caused by too much blood brought into a vessel due to arteriolar dilation ii. Example is dilation of arterioles in inflammation l. Passive hyperemia i. Caused from pressure build up due to blood not being able to drain from a vein ii. Ex. congestion 2. Develop a concept map of the pathway by which injured endothelium leads to a hemostatic plug or thrombus. Distinguish between intrinsic and extrinsic coagulation. a. Begins with platelet adherence to subedothelial structures resulting in a hemostatic plug. Requires von Willebrand factor. Platelets are then activated secreting their contents (which includes fibrinogen). The fibrinogen links the platelets. Blood coagulation generates fibrin that stabilizes the hemostatic plug forming a thrombus (white thrombus). b. Intrinsic coagulation is initiated by activation of Hageman factor. All other enzymes in series are produced in liver and found normally in the circulation. Extrinsic coagulation is activated by tissue factor (thromboplastin) which is released when endothelium is injured. 3. Identify the factors in Virchow’s triad and explain why they are important. Cite examples where each factor participates in thrombosis. a. Virchow’s triad is important because these conditions cause pathological thrombi. All three are important in causing VENOUS thrombosis. b. Endothelial Injury – exposes thrombogenic subendothelial collagen and their release of tissue factor c. Abnormal blood flow – disrupts the normal pattern of blood flow and causes endothelial injury. i. Stasis is a major factor in initiating venous thrombosis d. Hypercoagulability – genetic and acquired alteration sin coagulation that promote thrombosis. i. Most important defect is a mutation in Factor V (Factor V Leiden deficiency) that renders Factor V resistant to inactivation by protein C/Protein S (anti-thrombogenic pathway). ii. Acquired states include immobilization and cancer. e. Most common cause of arterial thrombi is atherosclerosis.
4. List four fates of thrombi. Describe the changes that occur during organization and recanalization of a thrombus. a. Dissolution via plasmin b. Propagation c. Organization and recanalization i. Oraganization is similar to a healing wound. Endothelial cells, smooth muscle cells, and fibroblasts move into the thrombus. Capillary channels may form and reestablish blood flow (recanalization). d. Embolization – thrombi dislodge from vessel wall and move to another site 5. Identify potential mechanisms that maintain the fluidity of blood and control the extent of thrombus formation at a site of injury. a. Thrombin when it comes in contact with intact endothelium causes the production of PGI-2 and NO which increases the blood flow through intact vessels around the site of injury. Intact endothelium also produced thrombomodullin and heparin sulfate that help inhibit coagulation. 6. Identify the biological importance of: a. Von Willebrand factor i. Needed for the adherence of platelets to subendothelium (collagen). ii. Produced by endothelial cells iii. Deficiency causes most common bleeding disorder b. Tissue factor i. Also known as thromboplastin and is made by endothelium ii. Is secreted by endothelial cells when they are injured and initiates the extrinsic pathway of coagulation. c. Thromboplastin i. Same as tissue factor d. Hageman factor i. Initiates the intrinsic pathway of coagulation when it is activated. ii. Activated when it comes in contact with collagen. e. Factor X i. Part of coagulation cascade ii. Activated via thromboplastin (minor) and by factor IX. It converts Prothrombin to thrombin with the help of Factor Va. f. Prothrombin i. Part of coagulation cascade ii. Is converted to thrombin via Factor Xa and Factor Va. g. Thrombin i. Part of coagulation cascade ii. Made from prothrombin (via the action of Factor Xa and cofactor factor Va) and converts Fibrinogen to Fibrin h. Thrombomodulin i. Binds and inactivates thrombin i. Protein C
i. Activated by thrombomodulin/thrombin complex j. Protein S i. Activated protein C binds to Protein S which then can inactivate Factors Va and VIIIa. By this means, excess thrombin tends to shut off coagulation. k. Factor 5 Leiden mutation i. Renders Factor V resistant to inactivation by Protein C/Protein S. l. Tissue plasminogen activator (TPA) i. TPA is produced by endothelium and is stimulated by thrombin. It converts plasminogen to plasmin which causes fibrinolysis. m. Heparin sulfate i. Binds to antithrombin and changes its configuration, allowing it to inhibit thrombin and several other coagulation factors. n. Other platelet inhibitors i. NO and PGI-2 7. Be able to recognize the gross and microscopic appearance of: a. Thrombus i. There is white, mixed, and red thrombi b. Embolus c. Post-mortem clot d. Recanalized thrombus 8. List several ways that emboli may form and identify some consequences of embolization. a. Broken bone causing a fat emboli (bone marrow) b. Deep sea divers creating an air embolus c. Emboli can cause infarcts 9. Define infarction and identify its cause. Distinguish red infarcts from white infarcts and cite examples where each may occur. a. Infarction is an area of coagulative necrosis caused by occlusion of either an artery or vein. b. Most are due to arterial occlusions by thrombi or emboli c. Red infarcts are venous occlusions or when the occlusion occurs in an area of duel blood supply. It is red due to hemorrhage. d. White (pale) infarcts occur in arterial occlusions. Inflammation: Systemic Effects 1. List several acute phase proteins and identify why they are important. a. Ceruloplasmin: a copper binding protein which is an anti-oxidant and superoxide scavenger. b. Complement C-3 forms opsonic and anaphylatoxic fragments c. Fibrinogen forms in the wound and serves as the initial matrix upon which repair occurs d. Haptoglobin binds iron preventing its loss in the urine e. Alpha-1-antitrypsin is the major inactivator of PMN elastase f. Plasma fibronectin binds to fibrinogen and in healing wounds stabilizes the wound clot and augments cell adhesion, migration, and phagocytosis
g. C-reactive protein activates complement promoting chemotaxis and phagocytosis, it also acts as an Fc dependent opsonin h. Serum amyloid A levels increase 100 to 1000 fold during acute inflammation i. Lipopolysaccharide binding protein (LBS) is a serum protein that binds lipopolysaccharide facilitating its removal by macrophages 2. Explain how local inflammation produces the following systemic effects: a. Leukocytosis i. Initial rise in leukocyte count is due to mobilization of marginated pools and increased release of neutrophils from the bone marrow. Prolonged infections induced proliferation of bone marrow precursors. b. Fever i. IL-1/TNF goes to brain stimulating production of PGE-2. PGE-2 activates vasomotor center resulting in autonomic nervous system vasoconstriction decreasing heat loss. There is also an increased metabolic activity. c. Elevated sedimentation rates i. Due to increased circulating fibrinogen levels d. Synthesis of acute phase proteins i. IL-6 causes liver protein synthesis to shift from albumin to acute phase proteins. IL-6 is produced by macrophages and by fibroblasts upon stimulation by IL-1/TNF. 3. Contrast the physiologic and pathologic effects of tumor necrosis factor, platelet activating factor, and interleukin 1. a. TNF Physiologic: i. Leukocyte adherence, Synthesis of tissue factor by endothelium, synthesis of IL-1 and PAF b. TNF Pathologic: i. Neutropenia, Disseminated intravascular coagulation (DIC), cachexia (generalized wasting), and can lead to heart failure c. IL-1 Physiologic: i. Local: leukocyte adherence, synthesis of tissue factor, fibroplasia, synthesis of PAF, induce production of IL-6 ii. System: Fever, sleep, anorexia, increase C3 levels, increase haptoglobin d. IL-1 Pathologic: i. Due to its ability to stimulate synthesis of PAF e. PAF Physiologic: i. Vasodilation, vascular leakage, PMN chemotaxis, Platelet activation f. PAF Pathologic: i. Shock, neutropenia (homotypic adhesion), thrombocytopenia and DIC 4. Describe the sequence of events believed to underlie the pathogenesis of septic shock.
a. LPS (Lipopolysaccharide) LPS-LPB complex interacts with macrophage CD14 LPS-CD14 complex activates toll-like receptor (TLR-4) induces macrophages to synthesize TNF-alpha stimulates production of IL-1 stimulates PAF production by endothelium b. LPS also activates complement (C5a) which activates neutrophils c. LPS also activates coagulation system with release of bradykinin d. IL-1/TNF causes: release of thromboplastin, upregulates adhesion molecules, endothelial production of IL-8 (activates LFA-1). These events cause leucopenia e. PAF causes vasodilation, vascular permeability causing shock 5. List major organ systems affected by shock and morphologic changes that may occur. a. Kidney i. Acute tubular necrosis (coagulative necrosis) b. Lung i. Neutrophil aggregation causes emboli in lungs. Activated neutrophils destroy alveolar walls by release of PMN elastase and generation of oxidants. ii. The alveolar damage [diffuse alveolar damage (DAD)] causes proteins to leak into the alveolar spaces that subsequently aggregate along the alveolar walls as hyaline membranes. iii. Shock lung or adult respiratory distress syndrome c. GI i. Mesenteric ischemia and hemorrhagic gastroenteropathy particularly of small bowel d. Liver i. Central lobular necrosis e. Heart i. Myocardial decompensation characterized by ventricular dilation and decreased ejection of blood. ii. TNF-alpha causes cardiac failure f. Brain i. Ischemic encephalopathy 6. Types of shock a. Cardiogenic i. Failure of myocardial function b. Hypovolemic i. Acute blood or fluid loss c. Septic i. Systemic inflammatory response syndrome d. Neurogenic i. Anesthesia or spinal cord injury e. Anaphylactic i. Hypersensitivity (constriction of airways)
Arteriosclerosis and Atherosclerosis 1. Define and be able to used in context the following terms: a. Atherosclerosis i. Loss of vessel elasticity of large elastic and medium sized muscular arteries ii. Affects the intima iii. Results from intima thickening resulting from lipid and smooth muscle accumulation iv. Does not affect intra-myocardial vessels and tends to involve proximal portions of the epicardial vessels (allows for coronary artery bypass grafting) v. Does not generally affect the internal mammary artery (internal thoracic artery), therefore, it is a good conduit for coronary artery bypass. b. Arteriosclerosis i. The term means a loss of vessel elasticity and is not a specific disease c. Arteriolosclerosis i. Loss of vessel elasticity of small arteries and arterioles ii. Affects the intima iii. Two types: hyaline and hyperplastic d. Atheroma i. A fatty deposit in the intima of an artery as a result of atherosclerosis. Also called an atherosclerotic plaque. e. Diffuse intimal thickening i. With aging or in response to injury, the intima thickens due to accumulation of smooth muscle cells. f. Stable plague i. Luminal surface is intact making ii. Probability of a thrombotic event is low g. Unstable plaque i. A plaque that has undergone surface change (ex. cap thinning leading to fissures or cracks) predisposing it to thrombosis. ii. When a fissure or crack extends into the necrotic core it could rupture leading to thrombosis. iii. Conditions that predispose to plaque rupture are areas of inflammation, a large lipid core, and a thin fibrous cap. h. Hard plaque i. Contains fibrous and/or calcified tissue and is rigid. ii. Can cause lumen stenosis iii. Not suitable for balloon angioplasty i. Soft plaque i. Contains a fatty core with necrotic debris, a cap that consists of smooth muscle cells and collagen, and is potentially moldable ii. Contains macrophages and lymphocytes (T-cells) mostly in core (chronic inflammation) and c-reactive protein
iii. Can cause lumen stenosis iv. Is suitable for balloon angioplasty 2. Be able to recognize the gross and microscopic appearance of: a. Foam cells i. Lipid laden cells that have been identified by monoclonal antibodies as macrophages or SMCs. ii. The lipid is mainly cholesterol esters derived almost exclusively from LDL. b. Fatty streaks i. Characterized by lipid accumulation within macrophages ii. Earliest recognized lesions of atherosclerosis iii. Flat lesion c. Hyalin arteriolosclerosis i. Characterized by hyalinization of the walls of arterioles increasing rigidity and decreasing lumen size ii. The hyalin is due to plasma proteins or extracellular matrix deposition iii. Predilection: elderly, diabetes, hypertension iv. Sites: kidney, spleen, GI, pancreas d. Hyperplastic arteriolosclerosis i. Characterized by increased SMCs in small arteries and arterioles that fixes lumen size and restricts capacity to dilate. ii. Associated with accelerated hypertension, fibrinoid necrosis iii. With accelerated HTN, plasma leaks into the vessel and deposits as fibrin with or without necrosis of smooth muscle (fibrinoid necrosis). e. Atheromatous plaques i. Intimal lesions that contain a superficial fibrous cap and a deeper core of extracellular lipid. ii. They are eccentric rather than concentric (circumferential). f. Complicated plaques i. Defined by the presence of calcification, ulceration, plaque rupture or hemorrhage into the plaque g. Monckeberg’s calcific sclerosis i. Loss of vessel elasticity of medium sized muscular arteries ii. Calcium deposits in the media iii. Does not cause stenosis, but does cause hard stiff arteries 3. Describe the relationship between hypertension and hyaline or hyperplastic arteriolosclerosis. a. The central lesion in HTN is a decrease in lumen size in resistant vessels (small muscular arteries and arterioles). With mild increase in pressure, there may be no morphologic changes. Moderate chronic HTN produces hyaline arteriolosclerosis. With more severe HTN, hyperplastic arteriolosclerosis develops. Note that hyaline arteriolosclerosis can be produced by conditions other than HTN such as diabetes and old age. 4. Contrast fatty streaks with atheromatous plaques (AP) with respect to:
5.
6.
7.
8.
a. Site of prevalence i. Fatty streaks occur in the thoracic region ii. AP occur in abdominal region b. Age of first appearance i. Fatty streak occur in newborns and older ii. AP occur in teens and older c. Reversibility i. Fatty streaks are reversible ii. AP are probably not reversible d. Clonality of smooth muscle proliferation i. Fatty streaks clonality is polyclonal (multiple cells proliferate) ii. AP clonality is monoclonal (proliferation is only in SMCs) Cite evidence that the fatty streak is not the precursor of atheromatous plaques. Cite evidence that favors such a transition. a. The fact that fatty streak has a minor SMC component, it is polyclonal, and occurs in the thoracic region compared to atheromatous plaques having a major SMC component, is monoclonal, and occurs in the abdominal region does not favor the idea that fatty streaks are the precursor to atheromatous plaques. b. Fatty streaks commonly occur earlier in life compared to atheromatous plaques and they each involve foam cells seem to indicate that fatty streaks may be precursors. Discuss the cellular origin of foam cells. Know the source of lipid in foam cells. a. Macrophages are phagocytic and internalize modified LDL via the scavenger receptor. Modified LDL results when lipid peroxides react with lysine residues on apoproteins making them recognizable by scavenger receptor. CRP also complexes with LDL in the arterial wall and facilitates uptake by macrophages via Fc receptor. b. Smooth muscle cells normally do no express scavenger receptors and can not be transformed into foam cells via LDL receptor uptake. However, scavenger receptors can be induced in SMCs by exposure to cytokines such as TNF-alpha or INF-gamma. Explain the contribution of each of the following to atherogenesis: a. Macrophages b. Cholesterol c. Low density lipoproteins d. Smooth muscle cells e. High density lipoproteins f. lymphocytes Identify the morphological and clinical significance of soft versus hard atheromatous plaques and stable versus unstable plaques. a. Stable plague i. Luminal surface is intact making ii. Probability of a thrombotic event is low b. Unstable plaque
i. A plaque that has undergone surface change (ex. cap thinning leading to fissures or cracks) predisposing it to thrombosis. ii. When a fissure or crack extends into the necrotic core it could rupture leading to thrombosis. iii. Conditions that predispose to plaque rupture are areas of inflammation, a large lipid core, and a thin fibrous cap. c. Hard plaque i. Contains fibrous and/or calcified tissue and is rigid. ii. Can cause lumen stenosis iii. Not suitable for balloon angioplasty d. Soft plaque i. Contains a fatty core with necrotic debris, a cap that consists of smooth muscle cells and collagen, and is potentially moldable ii. Contains macrophages and lymphocytes (T-cells) mostly in core (chronic inflammation) and c-reactive protein iii. Can cause lumen stenosis iv. Is suitable for balloon angioplasty 9. Identify the key growth factors for smooth muscle cells. a. These are the same for fibroblasts. PDGF causes smooth muscle cells to proliferate and TFF-beta causes SMC to produce collagen and ECM. 10. Know the most important clinical outcome of atherosclerosis of aorta and coronary artery. a. Aorta: Aneurysm b. Coronary artery: Stenosis and Thrombosis 11. Describe the reaction to injury hypothesis of atherogenesis and the monoclonal hypothesis of atherogenesis. a. Reaction to injury hypothesis: SM cells accumulate and proliferate in the arterial intima in response to injury similar to fibroblast accumulation at sites of repair during inflammation. i. Injury must alter endothelium increasing permeability and monocyte adherence. Injury must increase wall stress, by affecting the media. ii. Causes of injury: hemodynamic injury, hyperlipidemia, thrombi, viruses, immune. iii. For atherosclerosis to occur, there must be sustained injury that puts stress on the arterial wall and induces a chronic inflammatory response. b. Monoclonal hypothesis: SM cells undergo a mutation like event that confers a growth advantage so that this cell selectively proliferates in response to injury leading to a monoclonal SM cell accumulation. i. Initiator is a mutation caused by cholesterol epoxides, aryl hydrocarbons, or free radicals that damage DNA ii. Promoter is an agent that stimulates proliferation like injury or hypertension
c. It is probably a combination of the two hypotheses. Selection of SMC with a growth advantage (Monoclonal hypothesis) and an initiator of development of the atherosclerotic lesion (reaction to injury hypothesis). 12. List the major risk factors for the development of atherosclerosis. a. Hypertension, cigarette smoking, hyperlipidemia, diabetes, male sex, increased age.