General Pathology

General Pathology

1. Haemolysis

   • Extravascular: Normal, rarely pathological
     • Spleenic macrophages filter our blood and destroy old/ damaged RBC
       • Iron
         • Recycled and stored as Hs: haemosiderin is an orange-brown insoluble pigment of fe complexed loosely with proteins. Can be stored as ferritin
           • Haemosiderosis is the accumulation of Hs- organs in which its deposited become yellow-brown
             • caused by a systemic overload of Iron: haemolytic anaemia, blood transfusions
               • use a Prussin stain and it should stain blue-black
       • Heme
         • Broken down into Billirubin
           • This is an orange pigment which is released in the blood to become loosely coupled with albumin- FREE
             • Its insoluble, gets taken up by the liver and conjugated with Glucoronic acid to form conjugated bilirubin
               • Its excreted via the common bile duct, enters the duodenum and transformed into colourless substances: URObiliogens
                 • Some are resorbed and excreted in the urine after oxidation. Stercobilin is also an oxidised product that is secrted in faeces
                   • Excessive Billirubin in the blood and tissues= Jaundice/ Icterus
                     • Pre-Hepatic (Haemolytic)
                       • Excessive haemolysis which can be either EXTRA or INTRA- Lepto, mycoplasma, incompatible blood transfusions, neonatal- in all cases the release of billirubin may induce neoronal damage
                     • Hepatic (toxic)
                       • damage to the hepatocytes means that insufficently conjugate and excrete the billirubin- build up of unconjugated..canine hepatitis (CADV) and Cu toxicity causing hepatocellular necrosis
                     • Post-Hepatic (Obstructive)
                       • There is blockage of the bile duct system which impairs the secretion of CONJUGATED billirubin. *Intravascular obstruction, extrahepatic cholestasis, rupture of the vile ducts of Aplasia- no lumen forms so faeces appaer "white"
       • Globin: Recycled into AA and transported to liver
     • Pathological: incompatible blood transfusions, malaria, mycoplasma etc
   • Haemogllobin is a complex molecule made up of 4 globin proteins (each with a Heme molecule incoprporated) and a central iron atom
   • Intravascular: a pathological destruction of RBC within the blood vessels
     • Haemoglobinuria- some, but not all Hb will be filtered by the kidneys
       • Dark pink clouration of the urine
     • Haemoglobinaemia: Free Hb is circulated in the blood
       • Pink discolourtion of the plasma after centrifugation
     • caused by: Complement mediated immune reponses, damage to RBC- onion oxidative damage , red maple toxicity