Lecture 2 Flashcards
What does the onset and rate of PM changes depend on
- Environmental and body temperature 2. Cause of death
Are PM changes pathological
No, because it occurs after death
What must you refrigerate bodies and not freeze them
Intra and extracellular crystals disrupt cells and makes histopathological interpretation difficult
What tissues decompose more rapidly
GIT and nervous tissue
What do tissues need to be fixed in to be able to determine subtle histological changes
Formalin
Define Rigor Mortis
Contraction of muscles after death
Why does rigor mortis occur
Depletion of glycogen prevents synthesis of ATP after death and without ATP the muscle fibres do not relax, resulting in contraction of muscles and immobilisation of joints
What muscles have rigor mortis first
Involuntary muscles then voluntary muscles starting with the head and defending to the trunk and libs
When does rigor mortis occur
1-6 hours of death
How long can rigor mortis persist
1-2 days
What animals have stronger rigor mortis
Muscular animals
What accelerates onset of rigor
High temperature and activity before death
What animals may not show rigor mortis
Animals with cachexia or extreme malnutrition
What don’t animals with cachexia or extreme malnutrition show rigor
Because stores of ATP and glycogen are so low that contraction of myofibres is not possible
What is Algor Mortis
Gradual cooling of the cadaver
With algor what is cooling dependent on
Temperature
What not to confuse lens opacity with
Cataracts
What is another name for livor mortis
Hypostatic congestion
What is livor mortis/hypostatic congestion
Gravitational pull of blood to the down side of the animal
When does livor mortis/hypostatic congestion occur
Within an hour of death
where is livor mortis/hypostatic congestion seen
Externally in the skin
What colour animal is livor mortis/hypostatic congestion best seen in
On white animals
What do you get with bloating
Organ displacement
Where can you see livor mortis/hypostatic congestion internally the best
Lungs
What happens before the blood clots
Erythrocytes settle to the bottom of large vessels
What does the settlement of erythrocytes mean
2 portions - Bottom red mass - Upper pale yellowish mass
What is the bottom red mass known as
Red current jelly clot
What is the upper pale yellowish mass known as
Chicken fat clot
What is separation of blood clots dependent on
Erythrocyte sedimentation rate
What animal is Erythrocyte sedimentation rate high in
Horses and animals with systemic inflammatory reaction
Why is ESR high in animals with systemic inflammatory reaction
Increased plasma fibrinogen which causes erythrocytes to stack
What does post mortem clotting need to be distinguished from
Antimortem thrombi and thromboembolism
How do you remove the clot
Forceps
Describe postmortem clots
Unattached to vessel walls, tend to be shiny and wet and form a perfect cast of vessel lumens
Describe antimortem arterial thrombi
Attached, tend to be dry and duller and are laminated with tail extending downstream
Describe antimortem venous thrombi
Loosely attached and may resemble postmortem blots
Define autolysis
Breakdown/decomposition of cells after death
Why does decomposition upon death occur
- Failure to maintain ion gradient and cell membrane integrity 2. Cell membrane degrades and ruptures 3. Cell contents spill into interstitial and their cytology proteolytic enzymes further degrade exposed cells 4. Chain reaction of decomposition that results from digestion of tissue by intrinsic enzymes is called autolysis
What is another pathway for decomposition due to bacterial proliferation and consumption
Putrefaction (gas production and odours)
Explain putrefaction
Bacterial metabolism and dissolution of tissues result in colour and texture change - softening of tissues is due to autolysis of cells and actions of bacteria - Tissue becomes friable
After death the body decomposes. What is the first step and what occurs later on
- Autolysis 2. Bacterial putrefaction
What is the difference between mummification and maceration
Mummification is desiccation with no bacteria where maceration has bacteria
What does haemoglobin imbibition refer to
Pink/red staining of tissue
What occurs in haemoglobin imbibition
Haemoglobin from lysed erythrocytes penetrates vessel walls and surrounding tissues
Where is haemoglobin imbibition commonly seen
Heart and walls of large arteries and in veins several hours after death
Where is haemoglobin imbibition very obvious
In aborted foetuses that have been retained for several hours or days in the uterus
When does bile imbibition occur
Several hours after death
What happens with bile imbibition
Bile from gall bladder penetrates its wall and stains adjacent tissue yellowish green
Where is bile ambition seen
- Adjacent liver and intestines in contact with the gall bladder 2. Adjacent to large bile duct
What are some other post mortem changes
- Bloating - ruminants, horses 2. Organ displacement by gas in the intestinal tract 3. Pale areas in the liver 4. Mucosal sloughing in the rumen rapidly occurs 5. Bloody nasal discharge 6. Rectal or vaginal prolapse are usually artefacts
What is bloating difficult to distinguish from
Anti-mortem bloat (luminal tympany) in ruminants
Why do pale areas in the liver occur post mortem
Due to increased intra-abdominal pressure from gas filled intestines or focal action of postmortem bacteria
Why does Rectal or vaginal prolapse occur
due to gas distention of abdominal viscera
Why is bloat common in ruminants
Rumen microbes may produce abundant gas, causing carcass to swell tremendously
Explain
Lens opacity from cooling - algor mortis
Hypostatic congestion - livor mortis
Hypostatic congestion
Postmortem clotting
Postmortem autolysis
Haemoglobin imbition
Bile imbition
Rectal prolapse
