Medical brain notes 15

  EDEMA Edema is the presence of excess fluid in the intercellular space. It has many causes. ·              Increased hydrostatic pressure  causes edema in congestive heart failure (gen-eralized edema), portal hypertension, renal retention of salt and water, and venous thrombosis (local edema). ·              Hypoalbuminemia and decreased colloid osmotic pressure  cause edema inliver disease, nephrotic syndrome, and protein deficiency (e.g., kwashiorkor). ·              Lymphatic obstruction  (lymphedema) causes edema in tumor, following sur-gical removal of lymph node drainage, and in parasitic infestation (filariasis  →  elephantiasis). ·              Increased endothelial permeability  causes edema in inflammatio...

  HEMOSTASIS AND BLEEDING DISORDERS Hemostasis  is a sequence of events leading to the cessation of bleeding by the forma-tion of a stable fibrin-platelet hemostatic plug. It involves interactions between the vascular wall, platelets, and the coagulation system. Vascular Wall Injury Transient vasoconstriction is mediated by endothelin-1. Thrombogenic factors include a variety of processes: ·              Changes in blood flow cause turbulence and stasis favor clot formation.   ·              Release of tissue factor from injured cells activates factor VII (extrinsic pathway).   ·              Exposure of thrombogenic subendothelial collagen activates factor XII (intrin-sic pathway).   ·              Release of von Willebrand f...

  THROMBOSIS Thrombosis is the pathologic formation of an intravascular fibrin-platelet thrombus during life. Factors involved in thrombus formation ( Virchow’s triad ) include: ·              Endothelial injury due to atherosclerosis, vasculitis, or many other causes   ·              Alterations in laminar blood flow predisposing for DIC occur with stasis of blood (e.g., immobilization); turbulence (e.g., aneurysms); and hyperviscosity of blood (e.g., polycythemia vera)   ·                Hypercoagulability of blood can be seen with clotting disorders (factor V Leiden; deficiency of antithrombin III, protein C, or protein S); tissue injury (postoperative and trauma); neoplasia; nephrotic syndrome; advanced age; pregnancy; and oral contraceptives (estrogen increases synthetic activity ...

  EMBOLISM An embolism is any intravascular mass that has been carried down the bloodstream from its site of origin, resulting in the occlusion of a vessel. There are many types of emboli: ·              Thromboemboli:  most common (98%)   ·              Atheromatous emboli (severe atherosclerosis)   ·              Fat emboli (bone fractures and soft tissue trauma)   ·              Bone marrow emboli (bone fractures and cardiopulmonary resuscitation [CPR])   ·              Gas emboli cause decompression sickness (“the bends” and caisson disease) when rapid ascent results in nitrogen gas bubbles in the blood vessels   ·       ...

  INFARCTION Infarction is a localized area of necrosis secondary to ischemia. Common sites of infarction include heart, brain, lungs, intestines, kidneys. Infarcts have multiple causes. ·              Most infarcts (99%) result from thrombotic or embolic occlusion of an artery or vein.   ·              Less common causes include vasospasm and torsion of arteries and veins (e.g., volvulus, ovarian, and testicular torsion). On gross examination infarctions typically have a wedge shape, with the apex of the wedge tending to point to the occlusion. ·              Anemic infarcts (pale or white color)  occur in solid organs with a single bloodsupply such as the spleen, kidney, and heart.   ·              Hemorrhagic infarcts (red color...