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Weeks 4 and 5 Disturbances of Blood Flow

Weeks 4 and 5 Disturbances of Blood Flow. Dr.İ.Taci Cangül Bursa-2008. Disturbances of Blood Flow. Hyperemia and congestion Hemorrhage Ischemia Thrombosis Postmortem clots Disseminated intravascular coagulation Embolism Infarction Edema Shock. Hyperemia and Congestion.

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Weeks 4 and 5 Disturbances of Blood Flow

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  1. Weeks 4 and 5Disturbances of Blood Flow Dr.İ.Taci Cangül Bursa-2008

  2. Disturbances of Blood Flow • Hyperemia and congestion • Hemorrhage • Ischemia • Thrombosis • Postmortem clots • Disseminated intravascular coagulation • Embolism • Infarction • Edema • Shock

  3. Hyperemia and Congestion Increased volume of blood in an affected tissue or part • Hyperemia (active hyperemia): Arterial and arteriolar dilatation produces an increased flow of blood into capillary beds • Congestion (passive congestion or venous congestion): Impaired venous drainage

  4. Active Hyperemia Too much arterial blood is brought to an organ or tissue by dilated arterioles and capillaries • Sympathetic neurogenic mechanisms or • The release of vasoactive substances • Inflammatory reaction • Heat applied locally to a part • Increased physiological activity

  5. Can the increased blood flow (active hyperemia) in acute inflammation be a defense mechanism of the body?

  6. Passive Congestion • Blood leaving an organ or part is impeded (impaired venous drainage) • Grossly, the involved tissues appear bluish-red because of the poorly oxygenated venous blood • Microscopically, congestion is similar to hyperemia (capillaries and veins are dilated and filled with blood)

  7. Types of Passive Congestion • Localized passive congestion • Generalized passive congestion • Chronic generalized passive congestion of the lungs: Reduced left ventricular output (left-sided heart failure). • Chronic passive congestion of the liver: Right-sided heart failure (rarely from obstruction of the posterior vena cava).

  8. Hemorrhage The presence of erythrocytes outside the blood vessels • The vessel may be physically damaged so that erythrocytes flow out through a break in the wall (hemorrhage by rhexis) or • The erythrocytes may pass through an intact vascular wall by a process called diapedesis (hemorrhage by diapedesis)

  9. Naming Hemorrhage-1 • Petechiae • Ecchymoses • Purpura • Agonal hemorrhages • Linear hemorrhages • Paint-brush hemorrhages • Hemothorax • Hemopericardium

  10. Naming Hemorrhage-2 • Epistaxis • Hemoptysis • Enterorrhagia • Metorrhagia • Hematuria

  11. The Significance of Hemorrhage Depends on: (1) The volume of blood loss (2) The rate of blood loss, and (3) The site of hemorrhage

  12. Ischemia Local anemia or a deficiency of arterial blood to a portion of an organ or part. The chief causes of ischemia are: (1) External pressure upon an artery (2) Narrowing of the lumen of an artery (3) A thrombus or embolus

  13. Effects of Ischemia • The organ involved • The size of the vessel • The degree of occlusion • The degree of collateral circulation • End artery (as in kidneys): Acute necrosis • Gradual obstruction: Atrophy

  14. Thrombosis • Formation of a clot from elements of the circulating blood within the vascular system during life • May decrease or obstruct vascular flow causing ischemic/hypoxic injury to cells, tissues and organs • May become dislodged or fragmented to create emboli (an embolus is an intravascular mass carried in the bloodstream to some site remote from its origin)

  15. Factors Effective in Thrombosis (1) Injury to vascular endothelium (2) Alterations in normal blood flow (3) Alterations in the blood (hypercoagulability)

  16. Arterial vs Venous Thrombus • Grossly: Thrombi are friable, a mixture of red and gray in irregular layers, dull, and attached to the endothelium • Arterial thrombus: Dry, friable gray masses composed of almost regularly arranged layers of platelets and fibrin, irregularly mixed with small amounts of darker red coagulated blood (White or conglutination thrombus) • Venous thrombus: Red, gelatinous (Stasis or red coagulation thrombus)

  17. Nomenclature of Thrombi-I • Mural thrombi - are attached to the wall of the heart or blood vessel • Occluding thrombi - are attached to the entire circumference of the vessel • Valvular thrombi - are attached to the heart valves • Canalized thrombi - occur when new blood channels form in an organized thrombus

  18. Nomenclature of Thrombi-II • Saddle thrombi - straddle the bifurcation of blood vessels • Septic thrombi - are those which contain bacteria • Aseptic thrombi - are those that do not contain bacteria, etc.

  19. The Thrombus may … (1) increase in size and, by its enlargement, eventually cause obstruction of some critical vessel (2) give rise to emboli (3) be removed by fibrinolytic action or (4) become organized

  20. Disseminated Intravascular Coagulation (DIC) • Widespread microthrombi formation in capillaries, arterioles and venules • Composed largely of fibrin and aggregated platelets • A complication of a diverse group of clinical diseases in which there is activation of the intrinsic pathway of blood clotting

  21. Embolism • Process of a foreign body moving through the circulatory system and becoming lodged in a vessel causing obstruction • An embolus (plural, emboli) is a detached intravascular solid, liquid or gaseous mass that is carried by the blood to a site distant from its point of origin

  22. Infarction • A localized area of ischemic necrosis in an organ or tissue resulting from occlusion of either its arterial supply or venous drainage • Usually caused by thrombosis and/or embolism of the arterial blood supply • More rarely, external compression of vessels by expanding tumors, etc.

  23. Edema • Abnormal accumulation of fluid (water) in the intercellular tissue spaces or body cavities • Localized (e.g. obstruction of venous outflow from the leg) • Generalized in distribution (e.g. in chronic congestive heart failure)

  24. Nomenclature • Anasarca: Generalized edema in which fluid in subcutaneous tissues is especially prominent • Ascites: Collection of edematous fluid in the peritoneal cavity • Hydrothorax: Collection of edematous fluid in the thoracic cavity • Hydropericardium or Pericardial Effusion: Collection of edematous fluid in the pericardial sac

  25. Transudate-Exudate • Inflammatory edema is referred to as an exudate and it is associated with an inflammatory reaction • Non-inflammatory edema is referred to as a transudate

  26. Edema is caused by … (1) Decreased plasma osmotic pressure (2) Increased hydrostatic pressure (3) Increased permeability of vascular endothelium (4) Lymphatic obstruction

  27. Decreased Plasma Osmotic Pressure • Deficiency of blood proteins (hypoproteinemia) • Decreased formation or excessive loss • Albumin • More fluid is pushed into the intercellular spaces. Also, the force available to pull fluid into the bloodstream at the venous end of the capillary is reduced

  28. Decreased Plasma Osmotic Pressure-I • Malnutrition (starvation, emaciation) • Severe or advanced liver diseases (cirrhosis, etc.) • The loss of plasma proteins (intestine and kidneys)

  29. Decreased Plasma Osmotic Pressure-II • In the intestine, blood protein loss is usually the result of hemorrhage over a long period of time (stomach worms in sheep and cattle, slowly bleeding stomach ulcers in pigs and dogs, etc.) • In the kidneys, renal amyloidosis is the only frequently encountered condition in animals in which large volumes of blood protein are lost through the urine

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