Histochemical stains
Prussian blue – iron Congo red – amyloid Acid fast (Ziel-Neelsen, Fite) – acid-fast bacilli Periodic acid Schiff (PAS) – high carbohydrate content molecules Trichrome – cells and connective tissues Reticulin – collagen type III molecules
Antibody stains
Cytokeratin – epithelial cells Vimentin – cells of mesenchymal origin except the 3 muscle types; stains many sarcomas Desmin – smooth, cardiac, and skeletal myosin
Hematoxylin and Eosin
Hematoxylin: Stains blue to purple- Nucleus and nucleolus- Calcium- Bacteria Eosin: Stains pink to red- Cytoplasm- Collagen- Fibrin- RBCs- Thyroid colloid
Contents of platelet granules
Alpha granules:- Fibrinogen- Fibronectin- Factor V and vWF- Platelet factor 4- PDGR Dense bodies:- ADP- Ca2+- Histamine and serotonine- Epinephrin
Immune thrombocytopenia purpura (ITP)
Immune-mediated attack (usually IgG antiplatelet antibodies) against platelets leading to decreased platelets (thrombocytopenia) which result in petechiae, purpura (bruises), and a bleeding diathesis (eg, hematomas). - Antiplatelet antibodies against platelet antigens such as GpIIb-IIIa and GpIb-X (type II hypersensitivity reaction)- Antibodies are made in the spleen and the platelets are destroyed peripherally in the spleen by macrophages, which have Fc receptors that bind IgG-coated platelets. Acute ITP: Seen in children following a viral infection and is self-limitingChronic ITP: Usually seen in women in their childbearing years and may be the first manifestation of SLE. Labs:- Decreased platelet count, prolonged bleeding time- Normal prothrombin time and partial thromboplastin time- Peripheral blood smear: thrombocytopenia with enlarged immature platelets (megathrombocytes) Treatment: Corticosteroids, splenectomy
Thrombotic thrombocytopenic purpura (TTP)
Rare disorder of hemostasis in which there is a widespread intravascular formation of fibrin-platelet thrombi. It is sometimes associated with an acquired or inherited deficiency of the enzyme ADAMTS13, responsible for cleaving large multimers of von Willebrand factor. - Often affects adult women- Inclusion criteria: Microangiopathic hemolytic anemia and thrombocytopenia, with or without renal failure or neurological abnormalities.- Widespread formation of platelet thrombi with fibrin (hyaline thrombi) leading to intravascular hemolysis (thrombotic microangiopathy) Labs:- Decreased platelet count, prolonged bleeding time- Normal prothrombin time and partial thromboplastin time- Peripheral blood smear: thrombocytopenia, schistocytes, reticulocytosis Treatment: plasma exchange
Hemolytic uremic syndrome (HUS)
Thrombotic microangiopathy due to endothelial cell damage. - Occurs mostly in children, typically after a gastroenteritis (typically due to Shiga toxin-producing E coli 0157:H7) - Abdominal pain, diarhhea- Microangiopathic hemolytic anemia- Thrombocytopenia- Renal failure (more commonly than in TTP) - Kidneys show fibrin thrombi in the glomeruli
Coagulation factors
The intrinsic pathway is activated by the contact factors, which include:- Subendothelial collagen- High molecular weight kininogen (HMWK)- KallikreinXII → XIIa The extrinsic pathway is activated by the release of tissue factor (thromboplastin)VII → VIIa
Coagulation lab tests
Prothrombin time (PT): Tests extrinsic and common coagulation pathways- VII, X, V, prothrombin, fibrinogen- INR standardizes the PT Partial thromboplastin time (PTT): Tests instrinsic and common coagulation pathways- XII, XI, IV, VIII, X, V, prothrombin, fibrinogen Thrombin time (TT): Tests for adequate fibrinogen levels Fibrin degradation products (PDP): Tests fibrinolytic system (increased with DIC)
Thrombus vs blood clot
Thrombus- Location: Intravascular- Composition: Platelets, fibrin, RBCs and WBCs- Lines of Zahn: Present- Shape: Has shape Blood clot- Location: Extravascular or intravascular (postmortem)- Composition: Lacks platelets, fibrin, RBCs and WBCs- Lines of Zahn: Absent- Shape: Lacks shape
Major causes of shock
Cardiogenic shock (pump failure): myocardial infarction, cardiac arrhythmias, pulmonary embolism, cardiac tamponade Hypovolemic shock (reduced blood volume): hemorrhage, fluid loss secondary to severe burns, severe dehydration Septic shock (viral of bacterial infection): causes cytokines to trigger vasodilation and hypotension, ARDS, DIC, multiple organ dysfunction syndrome Neurogenic shock (generalized vasodilation): anesthesia, brain or spinal cord injury Anaphylactic shock (generalized vasodilation): type I hypersensitivity reaction
Atherosclerosis
Earliest (clinically reversible stage): Fatty streak - Grossly: yellow intimal streak and characterized - Microscopically: lipid-laden macrophages (foam cells) - Stable atheromatous plaques: Dense fibrus cap, small lipid core, less inflammation. Cause chronic ischemia. - Vulnerable atheromatous plaques: At risk for rupture, thrombosis or embolization due to composition (thin fibrous cap, large lipid core, dense inflammation).
Mönkeberg medial calcific sclerosis
Medial calcification of medium-sized (muscular) arteries, such as femoral, tibial, radial, and ulnar arteries. - Asymptomatic, but may be detected by x-ray.
Arteriolosclerosis
- Affects small arteries and arterioles. - Hyaline arteriolosclerosis: pink, glassy arterial wall thickening with luminal narrowing seen in benign hypertension, diabetes, and aging- Hyperplastic arteriolosclerosis: smooth-muscle proliferation resulting in concentric ("onion skin") wall thickening and luminal narrowing seen in malignant hypertension
Syphilitic aneurysms
Involve the ascending aorta in tertiary syphilis. Syphilitic aortitis causes an obliterative endarteritis of the vasa vasorum, leading to ischemia and smooth-muscle atrophy of the aortic media. Syphilitic aneurysms may dilate the aortic valve ring, causing aortic insufficiency.
Vascular ectasias
Nevus flammeus nuchae: Neck "birthmark" or "stork bite" that regresses. Port wine stain: Vascular birthmark that does not regress. Spider telangiectasias: Occur on the face, blanch with pressure, and are associated with pregnancy.
Glomus tumor
Benign, small, painful tumor of the glomus body that usually occurs under fingernails.