L2 - Pathogenesis

Alvaro

What is the definition of pathology?

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

What is the definition of lesions?

Lesions are anything abnormal in the body

What types of lesions are there?

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

What are some diagnostic investigations we can conduct to determine the pathology?

Gross lesions

Histological lesions

Cytology

Haematology and clinical biochemistry

Determining aetiology

What is somatic death?

Somatic death is the absence of life in a body

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

What is the order in which somatic cells die?

Cardiac myocells and neuronal cells first

Epithelial cells next

Finally fibrous tissue (bone) dies last.

Why is it important to understand the changes that happen post-mortem?

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)

What is the first post-mortem change that occurs?

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

What factors affect algor mortis?

1. Initial temperature
2. Insulation
3. Ambient conditions

What is the second post-mortem change?

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.

How long does rigor mortis take to set in? How long does it last for?

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

What is the third step in post-mortem changes?

Blood changes

What type of blood changes occur post-mortem?

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.

What step is post-mortem degeneration and what is it?

Step 4

Post-Mortem degeneration is decay and decomposition

What types of post-mortem degeneration occur?

Autolysis (self decomposition with enzymes)

Putrefaction (Bacteria proliferation)

What factors influence the rate of decay?

Temperature and presence of bacteria

What is the 4th step of post-mortem change? What types are there?

Colour changes.

* Haemoglobin imbibition
* Bile imbibition
* Pseudo-melanosis (False melanin staining)
* Pseudo-Necrosis (False nocrosis)

What is the 5th post-mortem change?

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

What are the final three (6, 7, 8) post-mortem changes?

6. Organ displacements
7. Mucosal sloughing in rumen
8. Lens opacity

Why is it important to understand post-mortem changes?

* Some post-mortem changes look like real lesions
* Sometimes post-mortem changes will obliterate the real lesions