L2 - Pathogenesis

The study of diseases and all the aspects that are involved with that disease

Lesions are anything abnormal in the body

Gross - can see with the naked eye

Microscopic - sometimes called histological, but typically require another tool to visualise the issue

Pathognomic - The lesion is associated with one cause only, or specific to a cause

Gross lesions

Histological lesions

Cytology

Haematology and clinical biochemistry

Determining aetiology

Somatic death is the absence of life in a body

Irreversible cessation of the vital functions of the brain, heart, and lungs

Cardiac myocells and neuronal cells first

Epithelial cells next

Finally fibrous tissue (bone) dies last.

Useful to determine the cause of death

Establish what a real lesion is and what is just post-mortem

Can help determine the post-mortem interval (Time since death)

Algor mortis - the changing of the internal body temperature to fit the ambient temperature

1. Initial temperature

2. Insulation

3. Ambient conditions

Rigor Mortis - Muscle fibre contractions due to loss of ATP production

This locks the actin to the myosin as ATP is required to release this binding within the muscle.

1-9 hours for ATP production to stop. Rigor will last for anywhere up to 36 hours after death, at which point the actin and myosin will decay which releases the muscle

Blood changes

Hypostatic congestion (Livor mortis) where blood will pool in one area of the body. This is typically the side of gravity

Post-mortem blood clotting. This is different to ante-mortem clots as they are typically smooth and in the shape of the vessel they are found within.

Step 4

Post-Mortem degeneration is decay and decomposition

Autolysis (self decomposition with enzymes)

Putrefaction (Bacteria proliferation)

Temperature and presence of bacteria

Colour changes.

• Haemoglobin imbibition

• Bile imbibition

• Pseudo-melanosis (False melanin staining)

• Pseudo-Necrosis (False nocrosis)

Gas production - bloating from the proliferation of anaerobic bacteria (Remember the exploding whale)

6. Organ displacements

7. Mucosal sloughing in rumen

8. Lens opacity

• Some post-mortem changes look like real lesions

• Sometimes post-mortem changes will obliterate the real lesions