Flashcards in PM Change Deck (21):
What should happen as soon as possible when cadavers are submitted?
They should be refrigerated especially if they are ruminants or horses (large amounts of abdominal viscera). Freezing should be avoided as the formation of ice crystals damages the tissue and hampers histological interpretation.
What is the definition of algor mortis?
Cooling of the body after death (time of death)
What is PM clotting of blood?
Blood coagulation in vessels- differentiate from ante mortem thrombi
What is hypostatic congestion?
The effect of gravity- seen in lungs and kidneys
What is Pseudomelanosis?
Green/black discolouration due to conversion of iron to iron sulphide by GI bacteria.
What is biliary imbibition?
Pigment imbibed into any organs that are in contact with it e.g. GIT
What is emphysema?
Invasion by gas producing bacteria.
What is rigour mortis and how does it form?
Begins 2-4hrs after death, it is the rigidity of skeletal muscles.
There is a burst of metabolic activity as substrates are depleted on cessation of circulation= decrease in pH, oxygen and ATP.
Ca efflux from SR= shortening of mm fibres.
Head and neck affected first then the extremities.
When should rigour mortis disappear and what can influence its onset?
As putrefaction begins (1-2days), should have completely disappeared after 72hrs.
Low glycogen= quick
high temp=faster onset
pH- higher in pyrexic animals so slower progression.
What is autolysis?
Release of intracellular enzymes that results in self digestion of tissues. It results in changes in the cytoplasm and nucleus that resemble those seen in necrosis, but there is no associated inflammatory response (differentiate by this!)
How does the rate of autolysis differ?
Mucosa of the stomach and intestine are very rapid whereas muscle and skin retain their structure for much longer. Bacterial involvement = rapid.
How does putrefaction occur?
When dead tissue is invaded by anaerobic organisms such as Clostridia- the tissue turns green/brown due to haemoglobin breakdown and formation of hydrogen sulphide.
What are agonal changes?
They occur around the time of death due to irreversible circulatory failure that leads to congestion in the vessels.
What do agonal changes look like?
Exaggerated in the lung- hypostatic pooling of blood in dependant sites. The spleen is particularly susceptible to congestion after barbituate euthanasia- this also shows crystals in the endocardium.
Can also be regurgitation of GI contents being in the alveoli or airways- GI intussusception.
What types of lesions can resemble neoplasia?
Nodular Hyperplasia- (inc. in number of cells), occurs when hyperplastic nodules of tissue develop in organs- multiple nodules of well-differentiated cells within a tissue.
Inflammatory lesions- can resemble neoplasia due in influx of inflammatory cells, combined fibrosis and reactive hyperplasia.
How can neoplasia be both a significant and insignificant finding?
If it is as a result of age, and is in a location that has room for expansion e.g. abdominal cavity and on the spleen. If it is in the spinal chord, where there is no potential space for expansion then it will be significant.
What are 3 examples of age-related changes?
Bones, joints an CT lose flexibility and become rigid.
Wear and tear to joints
Splenic siderofibrosis- yellow, dry encrustations on the capsule= local haemorrhage with subsequent deposits of Fe, Ca and fibrosis.
What changes can be seen in the lungs?
Anthracosis- polluted areas= inhaled carbon particles are phagocytosed by alveolar macrophages which become visible as multiple black foci in the lung tissue. The medulla of the trachebronchial lymphnode may also be black.
What changes can be seen in the vasculature?
Arteriosclerosis- common but incidental finding. Degeneration and proliferation in the arterial wall results in a loss of elasticity and hardening- obvious at branches of arteries.
Atherosclerosis- not common in animals except dogs with hyperthyroidism and hypercholesterolaemia- walls are thickened due to accumulation of cholesterol.
What drug associated changes can be seen?
1) local reaction- jugular v can be purple and swollen
2) Barbituate crystals
3) Splenomegaly- engorged with blood