Post Mortem Change
Factor
Autolysis
Digestion of tissue by own enzyme (pancreas, liver, kidney quickly, high proteolytic enzyme content)
Can be inhibited by inactivate or slow down enzyme
Refrigeration
Slow enzyme activity, allow necropsy performed later
Fixation: chemical inactivate enzyme, preserve for pathological process
Alcohol. formalin, mercury
Heating: denature enzyme
Canning
Algor mortis
Gradual cooling of body to environment T
Rate affected by insulation (body fat, hair coat) and ambient T
Livor mortis
Gravitational settling of blood at the ventral side
Cessation of blood flow, stagnation, settling
Dark red discolouration, seen in lungs and skin
1st sign: half to 2 hrs, full lividity at 8-12 hrs post mortem
Compress on rigid surface prevent settling on the region
Rigor mortis
Shortening, contraction of muscle to stiffening, immobilization
Circulation of blood stop, no O2 supplied, convert to anaerobic respiration, glycolysis, glycogen and ATP depleted, Ca flood --> contraction of muscle, myosin actin lock
Dissipates wt autolysis of myofilaments
Start from head, neck, trunk, limb and dissipates same order
Rate depends on glycogen storage (faster in emaciated animal), T, exercise
Start 1-6 hrs, gone in 1-2 days
Post mortem blood clotting
Circulation stop, no O2, endothelial cells died off, release thrombokinase initiate clotting wt leukocyte, thrombocyte
Heart, artery, vein
differentiate wt thrombus (pale, red, rough, attached firmly to vessel, injured vessels)
smooth, gelatinous Red / currant jelly (RBC homogenous clot, rapid clotting time), Yellow/ chicken fat (yellow plasma, WBC, fibrin above, red RBC below, slow clotting time/ rapid sedimentation, in horse high fibrinogen)
Persists until autolysed
Incomplete in septicaemia (Anthrax)
Putrefaction
Digestion by bacteria
Immune system x function, bacteria fermenting, overgrow
Digestive tract
Imbibition of hemoglobin
RBC break down (autolysis and putrefaction), Hb escape and stain the tissue red
More intense given longer time
Imbibition of bile
Cholebilirubin diffuse into surrounding tissue
Yellow pigmentation near gall bladder
Pseudomelanosis
Black pigment, stained by hydrogen sulfides produced by bacteria + iron in Hb = iron sulfide
Green, gray, black
Softening
Post mortem emphysema
Autolysis or putrefaction
Rapid in high T and high enzyme organ (liver, pancreas)
Accumulation of gas bubbles by putrefaction
Hydrogen sulfide most common
Kidney, liver
Distention
Bacteria fermentation in gut
Postmortem (pale liver, congested limbs) vs antemortem (esophageal bloat line)
Pressure on viscera, push blood out, pale liver and myocardium
Rupture of organs and tissues
vs antemortem: haemorrhage at edge
Bacteria fermentation, distended, rupture and hernia
Stomach, diaphragm, intestine, ventral wall
Displacement
Rolled over, causing intussusception, torsion, volvolus
Gas filled above, feed filled below
vs antemortem (congestion)